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# The Social Brain Hypothesis

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## Abstract

Conventional wisdom over the past 160 years in the cognitive and neurosciences has assumed that brains evolved to process factual information about the world. Most attention has therefore been focused on such features as pattern recognition, color vision, and speech perception. By extension, it was assumed that brains evolved to deal with essentially ecological problem-solving tasks. © 1998 Wiley-Liss, Inc.

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... Indeed, it has been found in a diverse range of social systems, including traditional hunter-gatherer groups and small-scale horticultural communities from across 5 continents as well as the armies of ancient Rome and most modern-day militaries [9]. In fact, the ENM is so ubiquitous that it can even be observed in many species of non-human primates, albeit with smaller group sizes [10]. The pervasiveness of the ENM is explained by Dunbar's Social Brain Hypothesis [10], which posits that primates have a hardwired cognitive limit that determines the maximum size and complexity of the social groups they can maintain; for humans, this is around 150 (Dunbar's number). ...
... In fact, the ENM is so ubiquitous that it can even be observed in many species of non-human primates, albeit with smaller group sizes [10]. The pervasiveness of the ENM is explained by Dunbar's Social Brain Hypothesis [10], which posits that primates have a hardwired cognitive limit that determines the maximum size and complexity of the social groups they can maintain; for humans, this is around 150 (Dunbar's number). Once this limit is surpassed, a social group will start to become unstable and fragment into smaller, more manageable groups [8]. ...
... As mentioned in the previous section, the ENM is a structure with an Ego at the centre, surrounded by groups of Alters in concentric circles. The ENM stems from the Social Brain Hypothesis [10] in anthropology, which posits that the social life of primates is constrained by the size of their neocortex. Accordingly, the typical group size for humans is estimated to be around 150 individuals (the famous Dunbar's number). ...
Preprint
The Ego Network Model (ENM) describes how individuals organise their social relations in concentric circles (typically five) of decreasing intimacy, and it has been found almost ubiquitously in social networks, both offline and online. The ENM gauges the tie strength between peers in terms of interaction frequency, which is easy to measure and provides a good proxy for the time spent nurturing the relationship. However, advances in signed network analysis have shown that positive and negative relations play very different roles in network dynamics. For this reason, this work sets out to investigate the ENM when including signed relations. The main contributions of this paper are twofold: firstly, a novel method of signing relationships between individuals using sentiment analysis and, secondly, an investigation of the properties of Signed Ego Networks (Ego Networks with signed connections). Signed Ego Networks are then extracted for the users of eight different Twitter datasets composed of both specialised users (e.g. journalists) and generic users. We find that negative links are over-represented in the active part of the Ego Networks of all types of users, suggesting that Twitter users tend to engage regularly with negative connections. Further, we observe that negative relationships are overwhelmingly predominant in the Ego Network circles of specialised users, hinting at very polarised online interactions for this category of users. In addition, negative relationships are found disproportionately more at the more intimate levels of the ENM for journalists, while their percentages are stable across the circles of the other Twitter users
... Instead of thinking more expansively, they think more narrowly as information increases. In essence, abundant information engenders a paradox: individuals cope with the availability of high levels of information by narrowing cognitively. 1 Similar to decision making choice sets, research on human sociality indicates that the human brain has a limited capacity to store and actively manage relationships (e.g., Dunbar, 1998;Dunbar & Spoors, 1995). Emotionally close ties are cognitively more salient and are stored in mental maps as core social information leading individuals on average to disproportionately emphasize closer ties (Binder, Roberts, & Sutcliffe, 2012;Dunbar, 1998;Dunbar & Spoors, 1995;Hill & Dunbar, 2003). ...
... In essence, abundant information engenders a paradox: individuals cope with the availability of high levels of information by narrowing cognitively. 1 Similar to decision making choice sets, research on human sociality indicates that the human brain has a limited capacity to store and actively manage relationships (e.g., Dunbar, 1998;Dunbar & Spoors, 1995). Emotionally close ties are cognitively more salient and are stored in mental maps as core social information leading individuals on average to disproportionately emphasize closer ties (Binder, Roberts, & Sutcliffe, 2012;Dunbar, 1998;Dunbar & Spoors, 1995;Hill & Dunbar, 2003). Just as individuals have limited time and energy to maintain many relationships, which may undermine the ability to focus on and perform creative tasks (Baer, 2010;Dahlander & Fredrisken, 2011;McFadyen & Cannella, 2004), individuals have limited cognitive capacities. ...
... For instance, in a supplemental analysis we found "inner circle" ties to be more frequently activated during idea elaboration: these ties could actually be not only what is actually used by creators, but also what is needed at this stage, rather than generic strong ties. Extant research on human sociality has shown that our minds clearly differentiate between inner circle and other types of strong ties (e.g., Dunbar, 1998;Hill & Dunbar, 2003). It may thus be that the type of strong tie matters, such that strongest, "inner circle" ties may be necessary. ...
Article
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Considering creativity as a journey beyond idea generation, scholars have theorized that different ties are beneficial in different phases. As individuals usually possess different types of ties, selecting the optimal ties in each phase and changing ties as needed are central activities for creative success. We identify the types of ties (weak or strong) that are helpful in idea generation and idea elaboration, and given this understanding, whether individuals activate ties in each phase accordingly. In an experimental study of individuals conversing with their ties, we provide evidence of the causal effects of weak and strong ties on idea generation and idea elaboration. We also find that individuals do not always activate ties optimally and identify network size and risk as barriers. Our results in a series of studies reveal that individuals with large networks, despite providing more opportunity to activate both strong and weak ties, activate fewer weak ties and are less likely to switch ties across phases than individuals with smaller networks, particularly when creativity is perceived as a high-risk endeavor. Finally, we find that activating the wrong ties leads to either dropping creative ideas or pursuing uncreative ones.
... The social brain hypothesis, and its use to predict a natural grouping size for humans (Dunbar's Number), was established through a series of empirical and theoretical studies beginning some thirty years ago (Dunbar 1992(Dunbar , 1993(Dunbar , 1998. Its origin lies in an attempt to understand why primate brains are so much larger than those of all other animals (Jerison 1973). ...
... brain) to handle the relationships involved. Over the decades, it has been established that: (1) there exists a statistical relationship between the typical size of a species' social group and the size of its neocortex, ostensibly derivative of selection for specialised cognition required for group-living (the social brain hypothesis) (Dunbar 1992(Dunbar , 1998Shultz & Dunbar 2022), (2) the quantitative form of this relationship applies only to primates (in other mammals and birds, the hypothesis takes the much simpler form of a qualitative switch between pairbonded and non-pairbonded species) , 2010, (3) the relationship actually consists of a set of four (possibly five) grades arranged in a fractal series that explains the multilevel structure of primate (and human) social systems (Dunbar 1993(Dunbar , 1998Kudo & Dunbar 2001;Hill & Dunbar 2003;Zhou et al. 2005;Hill et al. 2009;Sutcliffe et al. 2012;Dunbar & Shultz 2021a), (4) the grades differ in group size, brain size, social complexity, cognitive competences, and ecological context (Dunbar & Shultz 2021a), (5) the regression equation for the social brain relationship predicts a value of ~150 as the core group size for modern humans (Dunbar 1993), (6) there is now considerable empirical evidence that both the size of personal social networks and the size of natural social groups for humans is indeed ~150, and that this is nested within a fractal series of social layers (Dunbar 2020;Wang et al. 2016Wang et al. , 2021, (7) 150 is a stable value (an 'attractor') because it turns out to be a criticality (or phase transition point) in the efficiency of information flow in networks (West et al. 2019), and (8) at least in humans, the fractal structure is the product of a tradeoff between the time costs required to maintain different kinds of relationship and the benefits these provide (Sutcliffe et al. 2016;Tamarit et al. 2018Tamarit et al. , 2022. ...
... brain) to handle the relationships involved. Over the decades, it has been established that: (1) there exists a statistical relationship between the typical size of a species' social group and the size of its neocortex, ostensibly derivative of selection for specialised cognition required for group-living (the social brain hypothesis) (Dunbar 1992(Dunbar , 1998Shultz & Dunbar 2022), (2) the quantitative form of this relationship applies only to primates (in other mammals and birds, the hypothesis takes the much simpler form of a qualitative switch between pairbonded and non-pairbonded species) , 2010, (3) the relationship actually consists of a set of four (possibly five) grades arranged in a fractal series that explains the multilevel structure of primate (and human) social systems (Dunbar 1993(Dunbar , 1998Kudo & Dunbar 2001;Hill & Dunbar 2003;Zhou et al. 2005;Hill et al. 2009;Sutcliffe et al. 2012;Dunbar & Shultz 2021a), (4) the grades differ in group size, brain size, social complexity, cognitive competences, and ecological context (Dunbar & Shultz 2021a), (5) the regression equation for the social brain relationship predicts a value of ~150 as the core group size for modern humans (Dunbar 1993), (6) there is now considerable empirical evidence that both the size of personal social networks and the size of natural social groups for humans is indeed ~150, and that this is nested within a fractal series of social layers (Dunbar 2020;Wang et al. 2016Wang et al. , 2021, (7) 150 is a stable value (an 'attractor') because it turns out to be a criticality (or phase transition point) in the efficiency of information flow in networks (West et al. 2019), and (8) at least in humans, the fractal structure is the product of a tradeoff between the time costs required to maintain different kinds of relationship and the benefits these provide (Sutcliffe et al. 2016;Tamarit et al. 2018Tamarit et al. , 2022. ...
Preprint
Full-text available
The social brain hypothesis was proposed 30 years ago as an explanation for the fact that primates have much larger brains than all other animals. The claim was that primates live in unusually complex societies, and hence need a large 'computer' to manage the relationships involved. The core evidence subsequently provided in support of this claim was that there is a simple statistical relationship between the social group size characteristic of a species and the size of its brain, with humans fitting into this pattern. However, testing evolutionary hypotheses raises some challenging philosophical and statistical issues that are often overlooked, and great care is needed to ensure that we test the hypothesis we think we are testing. Here, I examine some of these challenges and illustrate the traps they can create for the unwary.
... Across diverse clades, sociality is hypothesized to drive brain size and structure. In primates, greater cognitive challenges associated with forming bonded social groups in large societies, among other influences (DeCasien et al., 2017;González-Forero and Gardner, 2018;DeCasien and Higham, 2019), appear to have selected for increased brain size (Dunbar, 1998;Dunbar andShultz, 2007, 2017;Meguerditchian et al., 2021). A broad phylogenetic perspective can be of significant value in exploring the evolution of nervous systems (Striedter et al., 2014;Keifer and Summers, 2016;Shigeno, 2017). ...
... Across diverse clades, sociality is hypothesized to drive brain size and structure. In primates, greater cognitive challenges associated with forming bonded social groups in large societies, among other influences (DeCasien et al., 2017;González-Forero and Gardner, 2018;DeCasien and Higham, 2019), appear to have selected for increased brain size (Dunbar, 1998;Dunbar andShultz, 2007, 2017;Meguerditchian et al., 2021). A broad phylogenetic perspective can be of significant value in exploring the evolution of nervous systems (Striedter et al., 2014;Keifer and Summers, 2016;Shigeno, 2017). ...
... The expensive tissue hypothesis (Aiello and Wheeler, 1995) posits that a trade-off in allocated resources from one expensive tissue (the brain) to another (the gut) was made possible by shifts to a higher quality diet in Homo, enabled in part by enhanced technological skills (Lepre et al., 2011), exploitation of diverse resources (Braun et al., 2010), and the invention of cooked foods through controlled fire (Wrangham, 2009;Herculano-Houzel, 2016). In addition to evidence that energetic constraints on encephalization may have been released by dietary shifts in early Homo, others have posited that brain expansion in early Homo may have been driven by the need for enhanced social intelligence (Dunbar, 1998;Dunbar and Shultz, 2017). With growing complexity in social life, perhaps associated with increased group size, brain expansion occurred. ...
Article
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Human brain size nearly quadrupled in the six million years since Homo last shared a common ancestor with chimpanzees, but human brains are thought to have decreased in volume since the end of the last Ice Age. The timing and reason for this decrease is enigmatic. Here we use change-point analysis to estimate the timing of changes in the rate of hominin brain evolution. We find that hominin brains experienced positive rate changes at 2.1 and 1.5 million years ago, coincident with the early evolution of Homo and technological innovations evident in the archeological record. But we also find that human brain size reduction was surprisingly recent, occurring in the last 3,000 years. Our dating does not support hypotheses concerning brain size reduction as a by-product of body size reduction, a result of a shift to an agricultural diet, or a consequence of self-domestication. We suggest our analysis supports the hypothesis that the recent decrease in brain size may instead result from the externalization of knowledge and advantages of group-level decision-making due in part to the advent of social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains contribute to the emergence of collective intelligence. Although difficult to study in the deep history of Homo, the impacts of group size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as models. The remarkable ecological diversity of ants and their species richness encompasses forms convergent in aspects of human sociality, including large group size, agrarian life histories, division of labor, and collective cognition. Ants provide a wide range of social systems to generate and test hypotheses concerning brain size enlargement or reduction and aid in interpreting patterns of brain evolution identified in humans. Although humans and ants represent very different routes in social and cognitive evolution, the insights ants offer can broadly inform us of the selective forces that influence brain size.
... Esto sugiere que la vida social es tan compleja que requiere estrategias cognitivas complejas y flexibles que les confieran a los individuos de un grupo la capacidad para reconocer, manipular y comportarse de acuerdo con estímulos sociales (como género, parentesco, estatus social, tenden-cias conductuales individuales, etc.) y hacer inferencias sobre lo que pueden hacer los otros en contextos específicos. Por lo tanto, se ha propuesto que estas especializaciones cognitivas para el mundo social producirían cerebros particularmente grandes, como dice la hipótesis de los cerebros sociales y especializados en el procesamiento de información social (Gazzaniga, 1985;Dunbar, 1998). Según esta hipótesis, el ambiente social no sólo ha producido cerebros especializados en la producción y procesamiento de información social, sino que, debido a este procesamiento tan complejo, toda la circuitería neuronal involucrada en dicho procesamiento debió haber aumentado durante la evolución social debido a las demandas cognitivas de la complejidad social como se ha demostrado en diversas especies de primates sociales en los que hay una correlación entre el tamaño de la neocorteza y la complejidad social (Dunbar, 1992(Dunbar, , 1993Dunbar & Shultz, 2007). ...
... No obstante, esto no significa que los problemas ecológicos no sean importantes para los animales sociales, sino que éstos son resueltos a través de la sociedad (Dunbar & Shultz, 2007). Diversos estudios (Dunbar, 1998;Barton & Dunbar, 1997;Dunbar & Bever, 1998;Schultz & Dunbar, 2006) señalan que, las variaciones en el tamaño y las proporciones del cerebro se pueden vincular con las capacidades cognitivas de diferentes especies y las correlaciones con la socioecología pueden dar pistas sobre los orígenes evolutivos de estas especializaciones. Por ejemplo, en primates no humanos, insectívoros, carnívoros, ungulados, murciélagos y cetáceos, se encontró un patrón común en la relación entre el tamaño del cerebro y el tamaño del grupo típico de la especie: cuanto más grande es el grupo, más grande es el cerebro; en general, se han encontrado correlaciones más estrechas entre el tamaño del grupo social y la neocorteza, un área que está notablemente ampliada en varios grupos de mamíferos de cerebro grande, incluidos primates, carnívoros y cetáceos (Byrne & Bates, 2007). ...
... Funciones de las habilidades socioemocionales Adolphs (2001) a diferencia de Ostrom (2006), propone que la cognición social es la capacidad de construir representaciones respecto a las relaciones entre uno mismo y los demás, y de usar flexiblemente tales representaciones para guiar una respuesta apropiada en las interacciones sociales de la vida cotidiana; para ello intervienen procesos que modulan el comportamiento, como son, la memoria, la toma de decisiones, la atención, la motivación y las emociones. En tal sentido, la percepción, el procesamiento e interpretación de información sobre el sí mismo, sobre otras personas (intenciones, disposiciones y comportamientos) y situaciones sociales, contribuyen a que los individuos continuamente realicen ajustes socioemocionales para cumplir con las normas de la sociedad en general (Dunbar, 1998). Al respecto, Ochsner (2008) propone un modelo de procesamiento socioemocional, que incluye habilidades sociales, cognitivas y afectivas con sus correlatos neurales específicos e interrelacionados, las cuales integran la respuesta a estímulos socioemocionales: 1) La adquisición de valores y respuestas socioafectivas. ...
Chapter
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... Today, the social brain hypothesis (SBH) is well established as an explanation for the link between large brains and intense sociality among the anthropoid primates [1][2][3][4][5]. The SBH argues that the need to live in large groups selected for increased brain size and, by extension, the cognitive capacities needed to ensure that these groups remain functional and cohesive. ...
... The SBH argues that the need to live in large groups selected for increased brain size and, by extension, the cognitive capacities needed to ensure that these groups remain functional and cohesive. In other words, it is an evolutionary hypothesis that explains how primates have solved the ecological problem of predation risk through the evolution of group-living, [6,7], and then solved the problem of inter-individual competition-which arises inevitably when animals are forced to live in close proximity to one another-by evolving large brains and complex cognitive capacities [1][2][3][4][5]. Support for this hypothesis has come from comparative studies of brain size and social life, in which Robin Dunbar and colleagues [1][2][3][4][5] have played a major role, as well as from studies of primate social behaviour and cognition, in both the wild and captivity [8][9][10][11][12][13][14][15][16]. ...
... In other words, it is an evolutionary hypothesis that explains how primates have solved the ecological problem of predation risk through the evolution of group-living, [6,7], and then solved the problem of inter-individual competition-which arises inevitably when animals are forced to live in close proximity to one another-by evolving large brains and complex cognitive capacities [1][2][3][4][5]. Support for this hypothesis has come from comparative studies of brain size and social life, in which Robin Dunbar and colleagues [1][2][3][4][5] have played a major role, as well as from studies of primate social behaviour and cognition, in both the wild and captivity [8][9][10][11][12][13][14][15][16]. In the case of the latter, the evidence presented is not directly tied to brains as such; rather, the objective is to establish the existence of the kinds of cognitive capacities that only a large brain can support (e.g. ...
Article
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The anthropoid primates are known for their intense sociality and large brain size. The idea that these might be causally related has given rise to a large body of work testing the ‘social brain hypothesis'. Here, the emphasis has been placed on the political demands of social life, and the cognitive skills that would enable animals to track the machinations of other minds in metarepresentational ways. It seems to us that this position risks losing touch with the fact that brains primarily evolved to enable the control of action, which in turn leads us to downplay or neglect the importance of the physical body in a material world full of bodies and other objects. As an alternative, we offer a view of primate brain and social evolution that is grounded in the body and action, rather than minds and metarepresentation. This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’.
... Lemurs are an ideal taxonomic group for conducting comparative studies because closely related species and genera have radiated into a diverse range of socioecological niches on Madagascar (Gould et al., 2007;Kappeler, 2012). This is particularly relevant to cognitive studies as there is debate regarding the relative effects of ecological and social pressures on brain size and learning mechanisms (social brain hypothesis: Dunbar, 1998; ecological intelligence hypothesis: Gibson, 1986). For example, assessing different learning processes exhibited during experimental tasks with taxa that inhabit different social and ecological niches can shed light on the selective pressures acting on cognitive abilities. ...
... Unlike haplorrhines (apes, monkeys, and tarsiers), group size in strepsirrhines (lemurs, lorises, galagos, and pottos) did not correlate with relative brain size but did correlate with performance on social cognition tasks (Maclean et al., 2009;Maclean et al., 2013). Group size is thought to drive cognitive complexity because of the necessity to maintain social bonds, remember interactions with many conspecifics, and track fluid rank relationships (Dunbar, 1998). Previous studies indicated that Lemur (who live in large multi-male, multifemale groups) equaled and even outperformed some monkeys in cognitive tests (Sandel et al., 2011;Jones et al., 2014;Devaine et al., 2017;Fichtel et al., 2020). ...
... Studying this behaviours and determining whether it can be exhibited by other taxa than primates is particularly important and would support the Social Brain Hypothesis. Dunbar (1998) proposed the Social Brain Hypothesis as an explanation for brain evolution. According to this concept, social complexity, not only the size of a social group (Dunbar, 2009) but also the importance and flexibility of social relationships, like fission-fusion society or monogamous bond (Shultz and Dunbar, 2007), would be the main constraint to shape evolution of the size of the brain in vertebrate taxa. ...
... Nonetheless, the fact that prosociality and reciprocity could be found outside primates supports the idea that social relationships could be a more important factor than mere phylogenetic proximity from humans to exhibit these behaviours. According to Dunbar's (1998Dunbar's ( , 2009) Social Brain Hypothesis, bonded relationships would be cognitively demanding enough to modulate the evolution towards a bigger brain (especially a bigger neocortex). Considering the scale of an individual's lifespan rather than evolution of species, Dale et al. (2020) highlighted the importance of social relationship over cognition for prosociality and cooperation tasks. ...
Article
Prosocial behaviours (providing benefits to a recipient with or without cost for the donor) have been found to be highly influenced by sex and by hierarchy. Rodents, in particular, are good model for studying prosocial responses, as they were found to exhibit intentional prosocial behaviours to reward a conspecific, and are very sensitive to reciprocity. In our study, we conducted a Prosocial Choice Test (PCT) in which four capybaras (Hydrochoerus hydrochaeris) living in a social group could choose between three tokens: choosing the prosocial token rewarded simultaneously the subject and a recipient, while choosing the selfish token only rewarded the subject; and choosing the null token provided no reward to anyone. Dominance within each dyad was also studied, both before and during the PCT experiment. Our results showed an influence of hierarchy: subjects were more prosocial towards the recipient when it was a subordinate than when it was a dominant individual. These results could be interpreted as a desire of strengthening a hierarchical rank regarding the subordinate, of punishing aggressive conspecifics (usually the subject's direct dominant), and of weakening dominant individuals in order to modify the pre-existing hierarchy. Additionally, our results highlighted a direct reciprocity phenomenon, a subject being more likely to be prosocial towards a prosocial recipient. All these findings suggest that prosociality could be well developed in other taxa than Primates and that, in long enough PCT experiments, subtle rules could influence individual prosocial strategies.
... Although research on social signature is just in its cradle, this phenomenon may turn to present a fundamental feature of human communication if it gets confirmed across different societies, types of communication, and communication channels. It will then be able to provide new evidence and development for a broader social brain theory proposed by evolutionary psychologist Robin Dunbar (Dunbar, 1998(Dunbar, , 2009) and continued in the respective stream of further research (Centellegher et al., 2017;Godoy-Lorite et al., 2016;Heydari et al., 2018;Liu et al., 2018;Saramäki, 2014;Sutcliffe et al., 2012). ...
... We suggest that further theory should develop around the explanation of variance of social signature and of its stability among individuals where both social and cognitive factors are likely to play a role. • We show that social brain hypothesis (Dunbar 1992(Dunbar , 1998(Dunbar , 2009 sustains in OSN private messaging as a communication channel, but suggest that the mechanism of OSNs' influence on the growth of individual social networks found by Wellman (2011) is different from a direct break-through Dunbar's number and that it should be captured by different research methods. • We confirm the relation between communication volume and emotional closeness, but simultaneously show that it significantly varies across individuals and thus enrich the social layers theory (Dunbar, 2016;Sutcliffe et al., 2012) by proposing to refocus it on the factors explaining individual variance. ...
Article
Social tie maintenance has always had cognitive and emotional costs and has been leading to uneven distribution of communication volume among interaction partners of individuals. This distribution, known as social signature, is assumed to be stable for each person. Availability of digital traces of human communication allows testing whether this assumption is true and whether it holds in specific channels of computer-mediated communication. In this paper, we investigate private messaging on a popular social networking website on a sample of 39 users and 8063 communication partners of those users over the period of 18 months. We find that this communication channel does not reduce cognitive costs as the overall number of users’ active contacts, on average, is equivalent to the cognitive limit known as Dunbar’s number. Confirming some previous research, we show that the volume of communication is unevenly distributed, related to emotional closeness, and that changes in this distribution (that is, the changes in social signature) over time within an individual are smaller than the distances between social signatures of different individuals. However, as an absolutely novel finding, we demonstrate that the changes within individuals are statistically significant, thus questioning the concept of social signature as a stable phenomenon.
... For example, a friend gifts you a sweater that you find hideous, but when asked how you like it, you respond with "thank you, this is very thoughtful of you!" Given the potential usefulness of bullshit as a method for navigating social systems, and with evidence that human intelligence may be set up largely for navigating the social world, an open question is whether bullshit ability as a behavioral feature reveals something about one's relative intelligence. If our brains have evolved for the purpose of manipulating information about social relationships (e.g., using tactical deception; Dunbar, 1998), then it is plausible that intelligent people will produce bullshit that is of higher quality, as a means of efficiently navigating their social surroundings. ...
... Overall, we interpret these results as initial evidence that the ability to bullshit well provides an honest signal of a person's ability to successfully navigate social systems, fitting the current work into existing frameworks whereby human intelligence is geared towards efficiently navigating such systems (Dunbar, 1998;Crow, 1993). More specifically, we propose that the ability to produce satisfying bullshit may have emerged as an energetically efficient strategy for achieving an individual's goals (such as acquiring status or impressing mates). ...
Article
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Navigating social systems efficiently is critical to our species. Humans appear endowed with a cognitive system that has formed to meet the unique challenges that emerge for highly social species. Bullshitting, communication characterised by an intent to be convincing or impressive without concern for truth, is ubiquitous within human societies. Across two studies ( N = 1,017), we assess participants’ ability to produce satisfying and seemingly accurate bullshit as an honest signal of their intelligence. We find that bullshit ability is associated with an individual’s intelligence and individuals capable of producing more satisfying bullshit are judged by second-hand observers to be more intelligent. We interpret these results as adding evidence for intelligence being geared towards the navigation of social systems. The ability to produce satisfying bullshit may serve to assist individuals in negotiating their social world, both as an energetically efficient strategy for impressing others and as an honest signal of intelligence.
... The size of egocentric networks has been observed to be higher for younger people and becomes more stable as they grow older 2,32 . The emotional closeness of an ego or focal individual with its alters (the individuals connected to the ego in each of these layers) is inversely proportional to the number of alters in the layer, with the innermost layer of around 5 alters (usually known as the support clique) consisting of the most intimate friendships and are the closest of all 24,33,34 . This layer commonly includes parents, siblings or close friends as well as romantic partners from the first layer and is the set of people the ego would rely on for advice, help and emotional support. ...
... However, when they form a close bond, even though calls initiated by both genders are not significantly different from each other (i.e. p values > 0.05 obtained from (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) year old) cohorts between peers and non-peers and having interactions with their opposite genders. The aggregated calls over four-month intervals over a span of three years have been calculated for the opposite-gender friendships for peers (having age differences of less than 10 years) exhibiting (a) formation of close bonds and (b) decaying of close bonds. ...
Article
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Humans are social animals and the interpersonal bonds formed between them are crucial for their development and well being in a society. These relationships are usually structured into several layers (Dunbar’s layers of friendship) depending on their significance in an individual’s life with closest friends and family being the most important ones taking major part of their time and communication effort. However, we have little idea how the initiation and termination of these relationships occurs across the lifespan. Mobile phones, in particular, have been used extensively to shed light on the different types of social interactions between individuals and to explore this, we analyse a national cellphone database to determine how and when changes in close relationships occur in the two genders. In general, membership of this inner circle of intimate relationships is extremely stable, at least over a three-year period. However, around 1–4% of alters change every year, with the rate of change being higher among 17-21 year olds than older adults. Young adult females terminate more of their opposite-gender relationships, while older males are more persistent in trying to maintain relationships in decline. These results emphasise the variability in relationship dynamics across age and gender, and remind us that individual differences play an important role in the structure of social networks. Overall, our study provides a holistic understanding of the dynamic nature of close relationships during different stages of human life.
... As developing the neural substrates for cognition is energetically demanding (Kool & Botvinick, 2013;Kotrschal et al., 2013), the evolution of cognitive skills involved in social tasks is expected to be strongly tied to levels of social complexity (the social brain hypothesis; Dunbar et al., 1998). According to this hypothesis, inhibitory control should be enhanced in those species in which social relationships are, on average, more complex (Bond et al., 2003;Byrne & Bates, 2007;Jolly, 1966;Kamil, 2004). ...
... Interestingly, our results on the plastic response of the guppies to social experiences early in life do not fit with the logic of the social brain hypothesis which predicts that more complex social environments should be linked to greater cognitive abilities on evolutionary timescales (Dunbar, 1998). Empirical support for the social brain hypothesis has been mostly drawn from primates (e.g. ...
Article
Living in a social group may impose cognitive demands, for example individual recognition, social memory and the inhibition of behaviour when it is not adaptive. As the neural substrates for these cognitive skills are metabolically expensive, cognitive abilities may be positively related to the complexity of the social system. Where there is large spatiotemporal variation in the ecological conditions experienced and hence in the social system exhibited by species, selection may favour adaptive phenotypic plasticity of cognitive abilities involved in social tasks rather than evolved differences across populations. Here, we tested this hypothesis in a social-living teleost fish, the guppy, Poecilia reticulata. We exposed new-born guppies to treatments that altered two parameters of social environmental complexity: group size (experiment 1) and group stability (experiment 2). Then, we assessed guppies' inhibitory control, the ability to withhold responding to a stimulus, a cognitive function that is critically involved in social interactions. In experiment 1, guppies reared alone showed higher levels of behavioural inhibition in a foraging task compared to guppies reared in pairs or in groups of six. In addition, we found that individuals' variance in performance was smaller for fish raised alone. In experiment 2, guppies reared in a stable social group showed greater inhibition than those from groups subjected to frequent fission–fusion events. These results reveal phenotypic plasticity of inhibitory control in guppies; however, contrary to prediction, they indicate greater inhibitory abilities developing in individuals exposed to ‘simpler’ social environments.
... Both of these changes can have effects on social interactions. Humans are inherently social beings (Dunbar, 1998(Dunbar, , 2003 and social interaction may even have had evolutionary advantages, in line with the social intelligence hypothesis (Tomasello, 2014). Social contacts can be a protective factor against psychological disorders such as depression (Peirce et al., 2000) and a lack of social contacts has been related to psychological distress (Cacioppo et al., 2014). ...
... Furthermore, perspective taking develops as a social skill at this age (van den Bos et al., 2011). In vulnerable phases of development, receiving appropriate social input plays a crucial role in human interactions (Dunbar, 1998(Dunbar, , 2003 and may provide evolutionary advantages (Tomasello, 2014). The government-mandated rules during the pandemic might thus, to some degree, prevent healthy social development in adolescence. ...
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During the COVID-19 pandemic, government-mandated protection measures such as contact restrictions and mask wearing significantly affected social interactions. In the current preregistered studies we hypothesized that such measures could influence self-reported mood in adults and in adolescents between 12 and 13 years of age, who are in a critical phase of social development. We found that mood was positively related to face-to-face but not to virtual interactions in adults and that virtual interactions were associated with negative mood in adolescents. This suggests that contact restrictions leading to a decrease in face-to-face compared to virtual interactions may be related to negative mood. To understand if prolonged exposure to people wearing masks during the pandemic might be related to increased sensitivity for subtle visual cues to others’ emotions from the eye region of the face, we also presented both age groups with the same standardized emotion recognition test. We found slightly better performance in emotion recognition from the eyes in our student sample tested during the pandemic relative to a comparable sample tested prior to the pandemic although these differences were restricted to female participants. Adolescents were also better at classifying emotions from the eyes in the current study than in a pre-pandemic sample, with no gender effects occurring in this age group. In conclusion, while social distancing might have detrimental effects on self-reported mood, the ability to recognize others’ emotions from subtle visual cues around the eye region remained comparable or might have even improved during the COVID-19 pandemic.
... Understanding the factors that shaped the evolution of the relatively large primate brain has been a topic of extensive debate, with multiple competing hypotheses postulated over the years [4]. Diet, increased social complexity and the energetic cost of brain tissue development and maintenance have been studied as predictors of brain size in primates [5][6][7]. Accumulating evidence points to diet as a main predictor of brain size across Primates [4,8,9], with factors like sociality playing an important role in certain groups (i.e. anthropoids, [10]). ...
... Combined, our results provide clear evidence for the effect of diet in the variation and integration of brain and dental morphology during strepsirrhine diversification. Furthermore, our results emphasise the differential effect of factors like diet and sociality have for the evolution of the brain across multiple primate groups [5,10], highlighting the importance of studying macroevolutionary processes at multiple phylogenetic scales. Given the unique evolutionary trajectory of the Aye-Aye in our results, we replicated our analyses while excluding it to test the sensitivity of our results. ...
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The evolution of the remarkably complex primate brain has been a topic of great interest for decades. Multiple factors have been proposed to explain the comparatively larger primate brain (relative to body mass), with recent studies indicating diet has the greatest explanatory power. Dietary specialisations also correlate with dental adaptations, providing a potential evolutionary link between brain and dental morphological evolution. However, unambiguous evidence of association between brain and dental phenotypes in primates remains elusive. Here we investigate the effect of diet on variation in primate brain and dental morphology and test whether the two anatomical systems coevolved. We focused on the primate suborder Strepsirrhini, a living primate group that occupies a very wide range of dietary niches. By making use of both geometric morphometrics and dental topographic analysis, we extend the study of brain-dental ecomorphological evolution beyond measures of size. After controlling for allometry and evolutionary relatedness, differences in brain and dental morphology were found between dietary groups, and brain and dental morphologies were found to covary. Historical trajectories of morphological diversification revealed a strong integration in the rates of brain and dental evolution and similarities in their modes of evolution. Combined, our results reveal an interplay between brain and dental ecomorphological adaptations throughout strepsirrhine evolution that can be linked to diet.
... 4 As research reviewed later in this chapter will make clear, every other effort to explain otherregarding behavior as fundamentally motivated by self-regarding interests has also failed. Dunbar (1998) demonstrated that the significant development of the neocortex in humans versus other primates is best explained by the species' advanced social development. The neocortex is the area of the mammalian brain involved in higher-order mental processes (e.g., analysis, planning, inferencing, and social relations). ...
... The problem with this development from an evolutionary perspective is the heavy cost to the organism's fitness that such brain development imposes. As Dunbar (1998) noted, "The adult human brain weighs about 2% of body weight but consumes about 20% of total energy intake" (1998, p. 178). Given the heavy cost of maintaining a large brain, "it is intrinsically unlikely that large brains will evolve merely because they can. ...
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The issue with Capitalism is more than economics. It is about the survival of humankind. This first-ever book to evaluate the effects of Capitalism from economic, societal, and evolutionary perspectives offers a detailed presentation of an alternative approach to commerce that is founded on the principles of individual freedom and property rights, yet it ensures that all commercial endeavors protect, nurture, and enrich human life and the ecosystem that supports all life. Capitalism, as a theoretical model of an imaginary world, is fine. Empirical evidence makes clear, however, that, as a practical economic system, Capitalism is a sham. Its dominance has undermined our understanding of ourselves as a species; commerce as our common means for enabling each other’s survival, growth, and fulfillment; and our notion of what constitutes appropriate conduct within a society and across societies internationally. It falsely pits individual emergence against social well-being when in fact each requires the other for its realization. This book documents the bases for Capitalism’s destructiveness including its false understanding of human nature and incorrect assumptions about the commercial context. It assumes that all people act egoistically without regard for others, and they do not. It also assumes that no asymmetries of information or power exist between buyers and sellers, and they do. Its theorems, drawn from these errors, construct a system that enables the few to exploit the many. As to human nature, studies repeated hundreds of times have shown that humankind displays two different response dispositions toward others. One portion always acts egoistically as Capitalism posits. Another portion is natively cooperative and other-regarding. For this latter segment, following Capitalism’s guidance requires them to behave in ways that contravene their native inclinations. And, it is the native human dispositions of this second segment of humankind that evolutionary science credits with enhancing our species’ ability to survive and evolve. The research reviewed in this book also clarifies the true nature of commerce; the breadth of human necessities, beyond material needs, that commerce must serve; Capitalism’s real utility as a “social control system”; and the potential consequences for evolved humankind of Capitalism’s universal promulgation.
... Robin Dunbar is well known for his alternative social brain hypothesis and the derivation of Dunbar's Number, the approximate species-typical number of social relationships that an individual can reasonably maintain. In humans this number is estimated at three to five people in close support cliques, about 12-20 with whom there are special ties and frequent contacts, and about 150 for acquaintances, which is roughly the size of the social networks of individuals in huntergatherer groups as well as functioning communities within modern complex societies (Dunbar, 1998). ...
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High levels of stress are known to accelerate biological aging in susceptible individuals, often leading to a downward course of ill health and early death. This book-length review explores how and why. It is too long to expect anyone to read the whole thing, but it serves to keep track of my understandings and syntheses (as of May 2022) while delving into literatures on toxic stress, aging, life history, and evolutionary theory. A common theme in these literatures is the connection between early life adversity (ELA) and later ill health and early death. Just about the only evolutionary explanation to be found is that ELA signals infants and children to develop a “live fast, die young” strategy to beat the odds against reproduction in their harsh environments, but this siphons energy from bodily maintenance leading to ill health later in life. However, the “live fast, die young” model has been increasingly questioned based on both theory and research. Even if it is valid in some cases, it must be incomplete because it is based on individual level theoretical reasoning. But humans and most primates live in social groupings that can only exist because individuals give up some degree of autonomy as they cooperate and support each other, especially their close relatives. This review takes the very rare approach of asking what happens if we assess the mass of ELA research through the lenses of inclusive fitness and multilevel selection, which were both developed to explain the puzzle of altruism. Is it possible there’s an altruistic aspect to accelerated biological aging? We arrive at an answer of “yes” in a multilevel model of stress and aging which appears to be particularly unique in simultaneously accounting for (1) inclusive fitness as a universal design principle; (2) the existential imperative to control free-riders (a concept virtually absent in the aging and stress literatures); (3) allometric scaling with body size determining baseline species-specific metabolic rates and lifespans (as reflected in the same lifetime limit in number of heartbeats across all mammal species); (4) social status hierarchies as venues of social selection which imposes distresses and eustresses based on relative current social and prospective fitness values of individuals; and (5) the tendency of high social distress to accelerate biological aging while eustress can maintain or even decelerate it, thereby (6) channeling individuals along diverging reproductive arcs which advantage higher status individuals, but disadvantage and speed the altruistic exit-by-aging of lower status individuals along with identified predatory free-riders.
... Communities arise and expire in irreversible, and roughly symmetric, fission events when social conflicts spiral out of control (Goodall 1986;Furuichi 1987;Feldblum et al. 2018). This becomes progressively more likely if group size increases and overburdens social cognitive mechanisms for handling conflicts and maintaining cohesion (Dunbar 1992(Dunbar , 1993(Dunbar , 1998. These events are under-researched but appear to be inherent to social features shared between Pan and Homo. ...
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Evolutionary Transitions in Individuality (ETI) have been responsible for the major transitions in levels of selection and individuality in natural history, such as the origins of prokaryotic and eukaryotic cells, multicellular organisms, and eusocial insects. The integrated hierarchical organization of life thereby emerged as groups of individuals repeatedly evolved into new and more complex kinds of individuals. The Social Protocell Hypothesis (SPH) proposes that the integrated hierarchical organization of human culture can also be understood as the outcome of an ETI-one that produced a "cultural organism" (a "sociont") from a substrate of socially learned traditions that were contained in growing and dividing social communities. The SPH predicts that a threshold degree of evolutionary individuality would have been achieved by 2.0-2.5 Mya, followed by an increasing degree of evolutionary individuality as the ETI unfolded. We here assess the SPH by applying a battery of criteria-developed to assess evolutionary individuality in biological units-to cultural units across the evolutionary history of Homo. We find an increasing agreement with these criteria, which buttresses the claim that an ETI occurred in the cultural realm.
... Whereas an increase in brain size probably played a role in early hominin evolution in terms of the social brain hypothesis (e.g., Dunbar, 1998;Pérez-Barbería et al., 2007), this aspect was less distinct between the later populations (Galway-Witham et al., 2019;Lombard and Högberg, 2021). Homo sapiens is known for the bulging of the parietal profile and a more rounded skull shape compared to all other homininspartly caused by the enlargement of the precuneus (e.g., Bruner et al., 2018;Bruner, 2021). ...
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Much has been written about Middle Stone Age hunting in southern Africa, yet there is no comprehensive overview for the development and use of stone-tipped hunting weapons. With this contribution, I use the tip cross-sectional area (TCSA) method to hypothesise about variation in weapon-assisted hunting strategies for the last 300,000 years or more. I assess and build onto previous hypotheses generated from similar approaches, introducing a larger sample from across the region. By also bolstering the standard TCSA ranges for javelin tips and stabbing/thrusting spear tips with more experimental and ethno-historical material, the method's interpretative robusticity is increased. The results indicate a general trend through time towards smaller weapon tips until reaching arrow-tip range during the MIS 4 glacial. Whereas light-weight javelins, similar to those used by African hunters today may have been in play since almost 200,000 years ago, it remains uncertain whether spearthrower-and-dart technology was ever used in southern Africa. Finally, I align the TCSA outcomes with climatic and demographic reconstructions and explain how human cognition interacts with technological adaptations such as the use of hunting weapons – demonstrating how the interplay between environment, demography, technology and cognition is integral to the development and understanding of Middle Stone Age weapon-assisted hunting strategies.
... Considering the results of Dunbar's initial research and the conception of the Social Brain Hypothesis in Dunbar (1998) the question can be raised in how far the patterns observed in the real-world apply similarly to an internet context (Dunbar 2012) or in particular, the context of Social Media platforms. A practical example for this assumption stems from Facebook's self-perception as a social network and its initial use of a limit of 5000 to the number of possible virtual friends (Ching et al. 2015). ...
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Based on the research done by Dunbar and the resulting Social Brain Hypothesis, the present study introduced a mathematical model for the development of follower numbers and the number of followed accounts regarding users/influencers of Social Media platforms. Under very simple assumptions the mathematical model suggests that an universal upper bound to follower and followed numbers exists. The theoretical upper bound is then empirically validated by using a representative data set of 255 influencers on Instagram from the field of women’s fashion. The follower numbers show convergence to a common boundary for the years 2018 to 2019 and stagnation for 2019 to 2020, while the number of followed accounts show stagnation for 2018 to 2019 and convergence for 2019 and 2020. The model in conjunction with its empirical validation therefore provides the mathematical background to establish the socio-biological Social Brain Hypothesis in the field of influencer marketing in regards to Social Media platforms.
... 10 According to the social brain hypothesis, Robin Dunbar argued that the cognitive demands of social life have served as the dominant selective pressure for mammalian brain size. 11 Specifically, cortical thickness increases with species' group size, particularly in regions associated with social cognition such as frontal polar, insular, and temporal cortices. 12,13 Individual differences in social network size may also be associated with increased volume of brain areas involved with affective and executive function, including the amygdala and prefrontal cortex. ...
Article
Social networks are the persons surrounding a patient who provide support, circulate information, and influence health behaviors. For patients seen by neurologists, social networks are one of the most proximate social determinants of health that are actually accessible to clinicians, compared with wider social forces such as structural inequalities. We can measure social networks and related phenomena of social connection using a growing set of scalable and quantitative tools increasing familiarity with social network effects and mechanisms. This scientific approach is built on decades of neurobiological and psychological research highlighting the impact of the social environment on physical and mental well-being, nervous system structure, and neuro-recovery. Here, we review the biology and psychology of social networks, assessment methods including novel social sensors, and the design of network interventions and social therapeutics.
... This number is smaller than expected by chance (Binomial test, p<1e -10 ), but these regions are proximal to genes enriched for cytoskeletal organization and processes related to synapse and neurotransmitter functions, among other GO terms (Permutation tests, p<0.05; Table S7; Fig. S6), potentially providing molecular support to hypotheses that the evolution of eusociality involves altered investments in cognitive function 40,41 . ...
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Life’s most dramatic innovations, from the emergence of self-replicating molecules to highly-integrated societies, often involve increases in biological complexity. Some groups traverse different levels of complexity, providing a framework to identify key factors shaping these evolutionary transitions. Halictid bees span the transition from individual to group reproduction, with repeated gains and losses of eusociality. We generated chromosome-length genome assemblies for 17 species and searched for genes that both experienced positive selection when eusociality arose and relaxed selection when eusociality was secondarily lost. Loci exhibiting these complementary evolutionary signatures are predicted to carry costs outweighed by their importance for traits in eusocial lineages. Strikingly, these loci included two proteins that bind and transport juvenile hormone (JH) – a key regulator of insect development and reproduction. Though changes in JH abundance are frequently associated with polymorphisms, the mechanisms coupling JH to novel phenotypes are not well understood. Our results suggest novel links between JH and eusociality arose in halictids by altering transport and availability of JH in a tissue-specific manner, including in the brain. Through genomic comparisons of species encompassing both the emergence and breakdown of eusociality, we provide insights into the mechanisms targeted by selection to shape a key evolutionary transition.
... Work by Robin Dunbar suggests that evolutionary increases in the size of primate groups produced new levels of social complexity, challenging and ultimately enhancing the interpretive capacity of the social brain and the use of vocalization to service relationships (Dunbar, 1992(Dunbar, , 1993(Dunbar, , 1998(Dunbar, , 2009; also see Gustison et al., 2012;Roberts and Roberts, 2019). These changes in neural and vocal complexity may have been as adaptive as alarm calls. ...
Article
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Many studies of primate vocalization have been undertaken to improve our understanding of the evolution of language. Perhaps, for this reason, investigators have focused on calls that were thought to carry symbolic information about the environment. Here I suggest that even if these calls were in fact symbolic, there were independent reasons to question this approach in the first place. I begin by asking what kind of communication system would satisfy a species’ biological needs. For example, where animals benefit from living in large groups, I ask how members would need to communicate to keep their groups from fragmenting. In this context, I discuss the role of social grooming and “close calls,” including lip-smacking and grunting. Parallels exist in human societies, where information is exchanged about all kinds of things, often less about the nominal topic than the communicants themselves. This sort of indexical (or personal) information is vital to group living, which presupposes the ability to tolerate, relate to, and interact constructively with other individuals. Making indexical communication the focus of comparative research encourages consideration of somatic and behavioral cues that facilitate relationships and social benefits, including cooperation and collaboration. There is ample room here for a different and potentially more fruitful approach to communication in humans and other primates, one that focuses on personal appraisals, based on cues originating with individuals, rather than signals excited by environmental events.
... Additionally, some theories have proposed that this interaction plays a vital role in human society (Fitch, 2006;Merker et al., 2009;Kirschner and Tomasello, 2010;Ravignani et al., 2014) because it has the function of building and facilitating social bonds among people, which contributes to the maintenance and development of a community. As people benefit from living in a large group (Dunbar, 1998), music performances and dances have spread across almost all cultures and communities. Recent studies have quantitatively suggested that people's relationships strengthen when they collectively participate in music or dance performances (Wiltermuth and Heath, 2009;Kirschner and Tomasello, 2010;Weinstein et al., 2016). ...
Article
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In the performing arts, such as music and dance performances, people actively interact with each other and show their exciting performances. Some studies have proposed that this interaction is a social origin of the performing arts. Some have further investigated this phenomenon based on the synchronization and coordination theory. Though the majority of these studies have focused on the collaborative context, several genres of the performing arts, such as jazz sessions and breakdance battles, have a competitive context. Several studies have suggested that, in this competitive context, performers actively interact with each other and construct some correspondence. Moreover, a few recent studies focusing on competitive conversations, such as debates, have shown that, compared to people's interactions in collaborative conversations, people in competitive contexts frequently coordinate their behaviors in complicated ways. However, the interaction and coordination among performers in these competitive contexts have not been sufficiently investigated. Therefore, we investigated the coordination of expert breakdancers in battle scenes and measured their rhythmic movements using a motion capture system. We calculated the relative phase of the rhythmic movements between two dancers to investigate their coordination. The results showed that the dancers' rhythmic movements tended to synchronize in an anti-phase fashion, which means that there were similarities as well as differences between the two dancers' rhythmic movements. Furthermore, this pattern of coordination changed dynamically as time elapsed, from an in-phase synchronization or leader-follower relationships to an anti-phase synchronization and then leader-follower relationships.
... According to the social brain hypothesis from anthropology (Dunbar 1998), the social life of primates is constrained by the size of their neocortex. Specifically, for humans, the typical group size is estimated around an average of 150 members, a limit that goes under the name of Dunbar's number. ...
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... The idea that language enables communication understood mostly as social information transfer is a premise that furthermore founded the field of evolutionary linguistics (Tomasello and Call 2007;Dunbar 1998;Hurford et al. 1998;Steels 2006). Pinker and Bloom (1990), for example, tried to synthesize the former schools by arguing that the biological faculty of language evolved by means of natural selection to enhance better social communication, understood as information transfer, at the sociocultural level. ...
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New definitions are proposed for communication and language. Communication is defined as the evolution of physical, biochemical, cellular, community, and technological information exchange. Language is defined as community communication whereby the information exchanged comprises evolving individual and group-constructed knowledge and beliefs, that are enacted, narrated, or otherwise conveyed by evolving rule-governed and meaningful symbol systems, that are grounded, interpreted, and used from within evolving embodied, cognitive, ecological, sociocultural, and technological niches. These definitions place emphasis on the evolutionary aspects of communication and language, and they are here differentiated from four older paradigms that instead focus either on the referential or social aspects of language, or the informational or semantic aspects of communication. In contrast with these paradigms, the definitions proposed here for communication and language are in line with a pluralistic evolutionary worldview, one that necessitates the recognition that a multitude of units, levels, mechanisms and processes are involved in bringing forth communication and language.
... Recently, there is an increasing awareness that colonization with gut microbes also plays an important role in the appropriate early-life development and functioning of the HPA axis in host species (Sudo, 2014;Foster et al., 2017), and raises intriguing questions about the role host microbes have in the phylogeny of the HPA axis. The role of the microbiome as an evolutionary driver of neuronal development has been examined in the context of the social brain hypothesis (Dunbar, 1998), which suggests that increased socialization between individuals favors the transmission of commensal bacteria that produce metabolites involved in regulating genes associated with cognition and anxiety (Stilling et al., 2014;Davidson et al., 2018). An adaptive component to microbiome variation could function to optimize social behavior, cognition, immunity, and host stress responses (Davidson et al., 2018). ...
Article
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Stress is broadly defined as the non-specific biological response to changes in homeostatic demands and is mediated by the evolutionarily conserved neuroendocrine networks of the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic nervous system. Activation of these networks results in transient release of glucocorticoids (cortisol) and catecholamines (epinephrine) into circulation, as well as activation of sympathetic fibers innervating end organs. These interventions thus regulate numerous physiological processes, including energy metabolism, cardiovascular physiology, and immunity, thereby adapting to cope with the perceived stressors. The developmental trajectory of the stress-axis is influenced by a number of factors, including the gut microbiome, which is the community of microbes that colonizes the gastrointestinal tract immediately following birth. The gut microbiome communicates with the brain through the production of metabolites and microbially derived signals, which are essential to human stress response network development. Ecological perturbations to the gut microbiome during early life may result in the alteration of signals implicated in developmental programming during this critical window, predisposing individuals to numerous diseases later in life. The vulnerability of stress response networks to maladaptive development has been exemplified through animal models determining a causal role for gut microbial ecosystems in HPA axis activity, stress reactivity, and brain development. In this review, we explore the evolutionary significance of the stress-axis system for health maintenance and review recent findings that connect early-life microbiome disturbances to alterations in the development of stress response networks.
... Rule of relation is derived from rule for the extended instinctive ingroup relations under collectivism worldview. The four instinctive ingroup relations in the social brain (Dunbar, 2016;Chung, 2020a) cracy. All high administrators in government had to be professionally qualified through the national examination system and the national promotion system (Tan & Geng, 2005). ...
... Is it more accurate to say there are concentric circles of in-groups, say from the brotherhood of man to ethnic groups, neighbors, and family? If so, is there a continuum of feelings of empathy, from a little blip for making a judgment of fairness for someone who went to the same high school to someone who likes the same hockey team to surges of empathy for intimate friends (Dunbar, 1998;de Waal, 1996)? Now that we have some clarity on the role of empathy, how can we characterize reasoned judgments, i.e. judgments based on critical comprehension and subsequent logical contemplation which result in decisions followed by actions? ...
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Empathy is expected to correlate with pro-social attitude s, but what effect does empathy have on judgments of distributive fairness? In our study, we found that participants with higher empathy scores on the Interpersonal Reactivity Index (IRI) were more likely to: (a) favor the use of egalitarian distribution when the joint effort is involved, and (b) deem overly self-interested or opportunistic behavior unfair. Female participants were more consistent in the exercise of moral judgments across diverse scenarios. Furthermore, empathy has several dimensions (e.g., perspective-taking or empathetic concern) and we observed that they interacted with gender and the nature of the hypothetical problem differently in some cases. Although the findings of the study are not counterintuitive, it has identified some avenues for further explorations and highlighted some potential methodological shortcomings of the IRI as a measure of empathetic traits.
... Crucially, both approaches can be extended to supply the evolutionary feedback dynamics necessary to explain the rapid expansion of brains and cognitive abilities in the human lineage. The leading version of the Social Brain Hypothesis, which we label the Machiavellian Intelligence Hypothesis (for clarity), proposes that big brains and sophisticated cognitive abilities result from the selection pressures for strategic thinking applied to managing relationships in larger, or more intensely social, groups (Byrne & Whiten, 1988;Whiten & Byrne, 1997;Dunbar, 1998). Favoured individuals, in this view, are better able to track and strategically deploy information, including about third parties, regarding the strategies or choices of others. ...
... There is vigorous debate about the selective pressures that originally favored increases in brain size and cognitive abilities in primates and about the most informative measure of brain size (Deaner et al., 2017). Supporters of the 'social brain hypothesis' cite evidence that various measures of brain size (e.g., the size of the neocortex in relation to the rest of the brain) are correlated with proxies of social complexity, such as social-group size and number of grooming partners (Dunbar, 1998(Dunbar, , 2003. However, others have argued that ecological pressures have favored increases in brain size Laland, 2001, 2002). ...
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... Hence, there is protracted opportunity for development of a complex web of differentiated social relationships among group members according to these various social distinctions. Indeed, the conclusion from many decades of research is that these different social relationships powerfully affect all manner of daily activities and have resulted in a highly developed "social acumen" (Jolly, 1966;Humphrey, 1976;Dunbar, 1998). ...
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In 1980, Robert Seyfarth, Dorothy Cheney and Peter Marler published a landmark paper in Science claiming language-like semantic communication in the alarm calls of vervet monkeys. This article and the career research program it spawned for its authors catalyzed countless other studies searching for semantics, and then also syntax and other rarefied properties of language, in the communication systems of non-human primates and other animals. It also helped bolster a parallel tradition of teaching symbolism and syntax in artificial language systems to great apes. Although the search for language rudiments in the communications of primates long predates the vervet alarm call story, it is difficult to overstate the impact of the vervet research, for it fueled field and laboratory research programs for several generations of primatologists and kept busy an equal number of philosophers, linguists, and cognitive scientists debating possible implications for the origins and evolution of language and other vaunted elements of the human condition. Now 40-years on, the original vervet alarm call findings have been revised and claims of semanticity recanted; while other evidence for semantics and syntax in the natural communications of non-humans is sparse and weak. Ultimately, we are forced to conclude that there are simply few substantive precedents in the natural communications of animals for the high-level informational and representational properties of language, nor its complex syntax. This conclusion does not mean primates cannot be taught some version of these elements of language in artificial language systems – in fact, they can. Nor does it mean there is no continuity between the natural communications of animals and humans that could inform the evolution of language – in fact, there is such continuity. It just does not lie in the specialized semantic and syntactic properties of language. In reviewing these matters, I consider why it is that primates do not evince high-level properties of language in their natural communications but why we so readily accepted that they did or should; and what lessons we might draw from that experience. In the process, I also consider why accounts of human-like characteristics in animals can be so irresistibly appealing.
... According to Dunbar (1993Dunbar ( , 1998Dunbar ( , 2009Dunbar ( , 2010Dunbar ( , 2016, humans have, on average, a stable social network of about 150 people (i.e., Dunbar's number). We, therefore, used Dunbar's number to calibrate the number of links between agents so that we arrive at an average degree d of 150. 31 Even though a real social network typically comprises millions of users, we restrict the simulated network size to a maximum of N = 500 agents due to computational feasibility. ...
Chapter
While organizational and business researchers have fruitfully applied evolutionary theory at various levels of analysis, few utilize organizational memetics to capture the complexity of organizational culture. This article contributes to bridging the gap between theorizing and empirical research on organizational memetics by raising and addressing the question if and how the diversity and interdependence of organizational memes can be captured. To tackle this exploratory question, the authors present a comprehensive literature review on organizational memetics and demonstrate how meme mapping can be used to highlight interdependencies among organizational memes based on the case of a German consulting firm. Besides revealing the most prominent memes in the complex memetic system of the organization, the meme map illustrates connections of varying strength among the organizational memes, thereby supporting the argument that organizational memetics can help to expose attractive memes that are important for both the stability and change of organizational cultures.
... To account for that, we consider separately those who have an unreasonably large number of friends and everyone else. We choose Dunbar's number (N = 150) as a threshold to separate these two groups as it is thought to be a soft upper limit of the personal social network size [35] and was empirically confirmed in both offline and online settings [36][37][38][39]. ...
Chapter
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As social interactions are increasingly taking place in the digital environment, online friendship and its effects on various life outcomes from health to happiness attract growing research attention. In most studies, online ties are treated as representing a single type of relationship. However, our online friendship networks are not homogeneous and could include close connections, e.g. a partner, as well as people we have never met in person. In this paper, we investigate the potentially differential effects of online friendship ties on mental health. Using data from a Russian panel study (N = 4, 400), we find that – consistently with previous research – the number of online friends correlates with depression symptoms. However, this is true only for networks that do not exceed Dunbar’s number in size (N ≤ 150) and only for core but not peripheral nodes of a friendship network. The findings suggest that online friendship could encode different types of social relationships that should be treated separately while investigating the association between online social integration and life outcomes, in particular well-being or mental health.
... First, animals may make sacrifices to increase the survival of other animals that share their genes, such as their offspring and relatives (Dawkins, 1989). Second, animals (especially humans) may make sacrifices for friends because they are part of a long-term assistance pact (i.e. a friendship) that benefits both parties (Dunbar, 1998;Fletcher et al., 2015). But neither of these situations applies to products or brands. ...
Article
Purpose Building meaningful relationships between consumers and service brands has received significant attention. This paper aims to explore how brand love in services – a relationship between the consumer and the service brand – is created through relationships between the consumer and other people. Specifically, we explore how brand love is created through the social relationships consumers form with other consumers. Design/methodology/approach This conceptual paper synthesizes the literature on consumer-brand relationships, brand community, social support and service providers, psychological ownership and brand love in the context of services. Findings This paper suggests that consumers love brands that are meaningful to them. Brands can become more meaningful to consumers by facilitating interpersonal connections and helping consumers define their identity. The connection between social relationships with other consumers and brand love is mediated by the consumer's level of perceived membership in the community. For some consumers, perceived membership grows to the point of becoming perceived psychological ownership of the community, where the consumer feels a sense of responsibility for the brand's and the community's well-being. Originality/value This paper advances theoretical understanding of how brand love operates in services and how it can be enhanced through services’ management.
... Similar to a few other studies, we observe that the volume of communication egos invest in transient alters is far from negligible, suggesting that such relationships are essential. In a broader context, our results uncover a new striking regularity in ego networks that reinforces related findings[6,17, 60, 52] of regularity and steadiness within the dynamics of communication. ...
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In contrast to stable relationships, far less is known about the temporal evolution of transient relationships, although these constitute a substantial fraction of people's communication networks. Previous literature suggests that ratings of relationship emotional intensity decay gradually until the relationship ends. Using mobile phone data from three countries (US, UK, and Italy), we demonstrate that the volume of communication between ego and its alters is stable for most of the duration of a transient relationship. Alters with longer durations receive more calls, with the duration of the relationship being predictable from call volume within the first few weeks of first contact. Relationships typically start with an early elevated period of communication, settling into the longer steady regime until eventually terminating abruptly. This is observed across all three countries, which include samples of egos at different life stages. These results are consistent with the suggestion that individuals initially engage frequently with a new alter so as to evaluate their potential as a tie, and then settle back into a contact frequency commensurate with the alter's match to ego on the so-called Seven Pillars of Friendship.
... The individuals may lose or gain friends in each of these layers 17,18 and the size of their egocentric networks has been observed to be higher for younger people and becomes more stable once they grow older 2,19 . The emotional closeness of an ego or focal individual with alters or individuals connected to the ego in each of these layers is inversely proportional to the number of alters in them, with the innermost layer consisting of the most intimate friendships and are the closest of all 12,20,21 . This layer includes parents, siblings or close friends as well as romantic partners from the first layer and they are the set of people the ego would rely on for advice, help and emotional support. ...
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Humans are social animals and the interpersonal bonds formed between them are crucial for their development and well being in a society. These relationships are usually structured into several layers (Dunbar's layers of friendship) depending on their significance in an individual's life with closest friends and family being the most important ones taking major part of their time and communication effort. However, we have little idea how the initiation and termination of these relationships occurs across the lifespan. To explore this, we analyse a national cellphone database to determine how and when changes in close relationships occur in the two genders. In general, membership of this inner circle of intimate relationships is extremely stable, at least over a three-year period. However, around 1-4% of alters change every year, with the rate of change being higher among 17-21 year olds than older adults. Young adult females terminate more of their opposite-gender relationships, while older males are more persistent in trying to maintain relationships in decline. These results emphasise the variability in relationship dynamics across age and gender, and remind us that individual differences play an important role in the structure of social networks. Overall, our study provides a holistic understanding of the dynamic nature of relationships during the life-course of humans.
... Yet, the larger the groups, the sparser the networks were, because every added individual added only 0.4 weak and 0.2 strong ties per group member in proximity and DSI networks. These patterns either suggest time constraints (Dunbar 1992) imposed by foraging on dispersed resources (Henzi et al. 1997), constraints on social cognition (Dunbar 1998), or network modularity increasing with group size (Kasper and Voelkl 2009). When released from time, space, and energy constraints as in captivity, macaques in small to medium-sized groups (7-25) do not show an increase in affiliation network density with increasing group size (Sueur et al. 2011b). ...
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It has long been recognized that the patterning of social interactions within a group can give rise to a social structure that holds very different places for different individuals. Such within-group variation in sociality correlates with fitness proxies in fish, birds, and mammals. Broader integration of this research has been hampered by the lack of agreement on how to integrate information from a plethora of dyadic interactions into individual-level metrics. As a step towards standardization, we collected comparative data on affinitive and affiliative interactions from multiple groups each of five species of primates to assess whether the same aspects of sociality are measured by different metrics and indices. We calculated 16 different sociality metrics used in previous research and thought to represent three different sociality concepts. We assessed covariation of metrics within groups and then summarized covariation patterns across all 15 study groups, which varied in size from 5 to 41 adults. With some methodological and conceptual caveats, we found that the number of weak ties individuals formed within their groups represented a dimension of sociality that was largely independent from the overall number of ties as well as from the number and strength of the strong ties they formed. Metrics quantifying indirect connectedness exhibited strong covariation with strong tie metrics and thus failed to capture a third aspect of sociality. Future research linking affiliation and affinity to fitness or other individual level outcomes should quantify inter-individual variation in three aspects: the overall number of ties, the number of weak ties, and the number or strength of strong ties individuals form, after taking into account effects of social network density. Significance statement In recent years, long-term studies of individually known animals have revealed strong correlations between individual social bonds and social integration, on the one hand, and reproductive success and survival on the other hand, suggesting strong natural selection on affiliative and affinitive behavior within groups. It proved difficult to generalize from these studies because they all measured sociality in slightly different ways. Analyzing covariation between 16 previously used metrics identified only three rather independent dimensions of variation. Thus, different studies have tapped into the same biological phenomenon. How individuals are weakly connected within their group needs further attention.
... Rearing animals in such enriched environments improves their learning and memory, increases synaptic arborization, and increases total brain weight (Van Praag et al., 2000). The second strand of biological reasoning concerns the "social brain hypothesis" for the evolutionary emergence of intelligence in the primate order (Dunbar, 1998). It is based on the observation that a species' brain size correlates well with its typical social group size (adjusted for overall body size). ...
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Advances in artificial intelligence often stem from the development of new environments that abstract real-world situations into a form where research can be done conveniently. This paper contributes such an environment based on ideas inspired by elementary Microeconomics. Agents learn to produce resources in a spatially complex world, trade them with one another, and consume those that they prefer. We show that the emergent production, consumption, and pricing behaviors respond to environmental conditions in the directions predicted by supply and demand shifts in Microeconomics. We also demonstrate settings where the agents' emergent prices for goods vary over space, reflecting the local abundance of goods. After the price disparities emerge, some agents then discover a niche of transporting goods between regions with different prevailing prices -- a profitable strategy because they can buy goods where they are cheap and sell them where they are expensive. Finally, in a series of ablation experiments, we investigate how choices in the environmental rewards, bartering actions, agent architecture, and ability to consume tradable goods can either aid or inhibit the emergence of this economic behavior. This work is part of the environment development branch of a research program that aims to build human-like artificial general intelligence through multi-agent interactions in simulated societies. By exploring which environment features are needed for the basic phenomena of elementary microeconomics to emerge automatically from learning, we arrive at an environment that differs from those studied in prior multi-agent reinforcement learning work along several dimensions. For example, the model incorporates heterogeneous tastes and physical abilities, and agents negotiate with one another as a grounded form of communication.
... Um exemplo deste tipo de desafio enfrentado atualmente por nossas mentes é o da manutenção das relações sociais. Dunbar (1998) sugere que a mente humana está apta a administrar informações sobre aproximadamente outras 150 ou pouco mais de 200 pessoas. Modelada em um contexto de relações sociais de pequenos grupos, a mente não estaria adaptada ao isolamento, como requerido pelas medidas de prevenção do distanciamento social e confinamento, tampouco bem adaptada ao convívio em multidões, como imposto pelas aglomerações dos grandes centros urbanos. ...
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Viral analogy models for the study of information distribution in the scope of human communication have been interdisciplinarily debated in different academic spheres, from naturalistic epistemiology (DENNET, 1995, 2017), through evolutionary biology (DAWKINS, 1976, 1993), genetics population (CAVALLI-SFORZA, 2000), mathematical modeling in evolutionary anthropology (BOYD; RICHERSON, 2005) and cultural epidemiology (SPERBER, 1985, 1994, 1996; WEISS, 2001; MORIN, 2016). In this essay, I propose the idea that in the same way - in a globalized world - diseases in human populations have the potential to spread pandemic orders (UJVARI, 2011), the globalized flow of information, under the impact of new cognitive technologies (DASCAL, 2005) also had ecological distribution potential exceeding epidemiological scales, reaching pandemiological levels. Therefore, I will seek to articulate the still embryonic notion of pandemiology (CASTIEL, 1995; ISPIR, 2020; AKERMAN; CASTIEL, 2021) and the Epidemiology of Representations (SPERBER, 1985, 1996; LERIQUE, 2017) in what I am proposing as a Pandemiology of Representations. Initially, I will introduce two well-established theories that characterize communication and how they are directly implicated in viral models for the study of ecological information distribution. Next, I will present the epidemiology of representations in their original formulation, suggesting its expansion towards a pandemiology of representations, in order to monitor/analyze projected information beyond an ecological boundary. Finally, I will seek to typify some of the phenomena that could be more closely studied in the context of the worsening public health crisis that is plaguing Brazil in the context of the COVID-19 pandemic.
... Our understanding of pattern and process in brain evolution in group-living animals benefits from sampling phylogenetically diverse species. Ants and other eusocial insects (primarily wasps, bees, and termites) have become important models to explore what is broadly conceptualized as "social brain evolution" (Dunbar, 1998;Lihoreau et al., 2012Lihoreau et al., , 2019Godfrey and Gronenberg, 2019;Muratore and Traniello, 2020;Coto and Traniello, 2021). Eusocial insects have exceptional reproductive and ergonomic polyphenisms associated with division of labor and highly cooperative behavior, and thus offer multiple opportunities and a rich array of species to examine how reproductive competence, sterility, and morphological and behavioral differentiation impact social roles and neuroarchitecture. ...
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Current methods used to quantify brain size and compartmental scaling relationships in studies of social insect brain evolution involve manual annotations of images from histological samples, confocal microscopy or other sources. This process is susceptible to human bias and error and requires time-consuming effort by expert annotators. Standardized brain atlases, constructed through 3D registration and automatic segmentation, surmount these issues while increasing throughput to robustly sample diverse morphological and behavioral phenotypes. Here we design and evaluate three strategies to construct statistical brain atlases, or templates, using ants as a model taxon. The first technique creates a template by registering multiple brains of the same species. Brain regions are manually annotated on the template, and the labels are transformed back to each individual brain to obtain an automatic annotation, or to any other brain aligned with the template. The second strategy also creates a template from multiple brain images but obtains labels as a consensus from multiple manual annotations of individual brains comprising the template. The third technique is based on a template comprising brains from multiple species and the consensus of their labels. We used volume similarity as a metric to evaluate the automatic segmentation produced by each method against the inter- and intra-individual variability of human expert annotators. We found that automatic and manual methods are equivalent in volume accuracy, making the template technique an extraordinary tool to accelerate data collection and reduce human bias in the study of the evolutionary neurobiology of ants and other insects.
... Studies combining neuroimaging techniques and cognitively demanding tasks show that individual differences in the volume of the orbitofrontal cortex (a specific region of the neocortex) explained differences in mentalising skills, and those, in turn, were able to explain differences in network size. 9 In fact, according to the Social Brain Hypothesis, 10 the size of a personal (active) relationship network is limited by the size of the neocortex 11 to contain about 150 individuals (Dunbar's number). ...
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We discuss the structure of human relationship patterns in terms of a new formalism that allows to study resource allocation problems where the cost of the resource may take continuous values. This is in contrast with the main focus of previous studies where relationships were classified in a few, discrete layers (known as Dunbar's circles) with the cost being the same within each layer. We show that with our continuum approach we can identify a parameter $\eta$ that is the equivalent of the ratio of relationships between adjacent circles in the discrete case, with a value $\eta\sim 6$. We confirm this prediction using three different datasets coming from phone records, face-to-face contacts, and interactions in Facebook. As the sample size increases, the distributions of estimated parameters smooth around the predicted value of $\eta$. The existence of a characteristic value of the parameter at the population level indicates that the model is capturing a seemingly universal feature on how humans manage relationships. Our analyses also confirm earlier results showing the existence of social signatures arising from having to allocate finite resources into different relationships, and that the structure of online personal networks mirrors those in the off-line world.
... The presence of the threshold η finds its ground reason in the anthropological literature. In fact, according to the social brain hypothesis developed by Dunbar [63] and verified in several experiments [64,65], to model the user's social relationships, η can be surely set to 150, which represents the human cognitive limit to the number of people with whom an individual can maintain stable social relationships. Such characteristic allows the model to dynamically keep track of the changes in the structure of the user's social relationships. ...
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Context modeling and recognition represent complex tasks that allow mobile and ubiquitous computing applications to adapt to the user's situation. Current solutions mainly focus on limited context information generally processed on centralized architectures, potentially exposing users' personal data to privacy leakage, and missing personalization features. For these reasons on-device context modeling and recognition represent the current research trend in this area. Among the different information characterizing the user's context in mobile environments, social interactions and visited locations remarkably contribute to the characterization of daily life scenarios. In this paper we propose a novel, unsupervised and lightweight approach to model the user's social context and her locations based on ego networks directly on the user mobile device. Relying on this model, the system is able to extract high-level and semantic-rich context features from smartphone-embedded sensors data. Specifically, for the social context it exploits data related to both physical and cyber social interactions among users and their devices. As far as location context is concerned, we assume that it is more relevant to model the familiarity degree of a specific location for the user's context than the raw location data, both in terms of GPS coordinates and proximity devices. By using 5 real-world datasets, we assess the structure of the social and location ego networks, we provide a semantic evaluation of the proposed models and a complexity evaluation in terms of mobile computing performance. Finally, we demonstrate the relevance of the extracted features by showing the performance of 3 machine learning algorithms to recognize daily-life situations, obtaining an improvement of 3% of AUROC, 9% of Precision, and 5% in terms of Recall with respect to use only features related to physical context.
... Neuroecology, the comparative study of mechanisms that underlie cognitive capacity, has provided robust support for the adaptive nature of cognitive differences in social insects in terms of brain evolution (Kamhi et al., 2016;Godfrey and Gronenberg, 2019). Based on these findings that support the classic idea that social evolution is one of the strongest drivers of brain evolution (Dunbar, 1998;Dunbar and Shultz, 2007), social insects are particularly suited to understanding how cognitive trait evolution is related to sociality. ...
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Cognitive variation is proposed to be the fundamental underlying factor that drives behavioral variation, yet it is still to be fully integrated with the observed variation at other phenotypic levels that has recently been unified under the common pace-of-life framework. This cognitive and the resulting behavioral diversity is especially significant in the context of a social group, the performance of which is a collective outcome of this diversity. In this review, we argue about the utility of classifying cognitive traits along a slow-fast continuum in the larger context of the pace-of-life framework. Using Tinbergen’s explanatory framework for different levels of analyses and drawing from the large body of knowledge about honeybee behavior, we discuss the observed interindividual variation in cognitive traits and slow-fast cognitive phenotypes from an adaptive, evolutionary, mechanistic and developmental perspective. We discuss the challenges in this endeavor and suggest possible next steps in terms of methodological, statistical and theoretical approaches to move the field forward for an integrative understanding of how slow-fast cognitive differences, by influencing collective behavior, impact social evolution.
... Certain key resources such as air, water, and food are crucial for animal survival, and thus also human psychology includes motivational mechanisms that have developed to ensure that the organism behaves in ways that typically lead to the acquisition of these key resources. However, a social animal like human being designed to live in relatively large tribes (Dunbar, 1998) have developed motivational dispositions that go beyond mere acquisition of food and water. The survival and reproduction opportunities of a human individual have been highly dependent on one's position and reputation within one's tribe. ...
... The presence of the threshold η finds its ground reason in the anthropological literature. In fact, according to the social brain hypothesis developed by Dunbar [63] and verified in several experiments [64,65], to model the user's social relationships, η can be surely set to 150, which represents the human cognitive limit to the number of people with whom an individual can maintain stable social relationships. Such characteristic allows the model to dynamically keep track of the changes in the structure of the user's social relationships. ...
Article
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Context modeling and recognition represent complex tasks that allow mobile and ubiquitous computing applications to adapt to the user’s situation. The real advantage of context-awareness in mobile environments mainly relies on the prompt system’s and applications’ reaction to context changes. Current solutions mainly focus on limited context information generally processed on centralized architectures, potentially exposing users’ personal data to privacy leakage, and missing personalization features. For these reasons on-device context modeling and recognition represent the current research trend in this area. Among the different information characterizing the user’s context in mobile environments, social interactions and visited locations remarkably contribute to the characterization of daily life scenarios. In this paper we propose a novel, unsupervised and lightweight approach to model the user’s social context and her locations based on ego networks directly on the user mobile device. Relying on this model, the system is able to extract high-level and semantic-rich context features from smartphone-embedded sensors data. Specifically, for the social context it exploits data related to both physical and cyber social interactions among users and their devices. As far as location context is concerned, we assume that it is more relevant to model the familiarity degree of a specific location for the user’s context than the raw location data, both in terms of GPS coordinates and proximity devices. We demonstrate the effectiveness of the proposed approach with 3 different sets of experiments by using 5 real-world datasets collected from a total of 956 personal mobile devices. Specifically, we assess the structure of the social and location ego networks, we provide a semantic evaluation of the proposed models and a complexity evaluation in terms of mobile computing performance. Finally, we demonstrate the relevance of the extracted features by showing the performance of 3 different machine learning algorithms to recognize daily-life situations, obtaining an improvement of 3% of AUROC, 9% of Precision, and 5% in terms of Recall with respect to use only features related to physical context.
... Current debate regarding the drivers of brain expansion and cognition in animals have primarily focused on the relative roles of social and ecological factors (Navarrete et al. 2016;Street et al. 2017). According to the "Social intelligence hypothesis", social challenges posed by group-livings, like the need to understand and anticipate the behavior of conspecifics, are the key drivers of enhanced cognition and enlarged brains (Byrne and Whiten 1988;Dunbar 1998). By contrast, the "Ecological intelligence hypothesis" states that ecological challenges like the need to exploit a wide variety of food or to access food that is difficult to obtain are the most important selective factors shaping cognitive skills and larger brains (Miltion 1988). ...
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Despite important recent advances in cognitive ecology, our current understanding of avian cognition still largely rests on research conducted on a few model taxa. Vultures are an ecologically distinctive group of species by being the only obligate carrion consumers across terrestrial vertebrates. Their unique scavenging lifestyle suggests they have been subject to particular selective pressures to locate scarce, unpredictable, ephemeral, and nutritionally challenging food. However, substantial variation exists among species in diet, foraging techniques and social structure of populations. Here, we provide an overview of the current knowledge on vulture cognition through a comprehensive literature review and a compilation of our own observations. We find evidence for a variety of innovative foraging behaviors, scrounging tactics, collective problem-solving abilities and tool-use, skills that are considered indicative of enhanced cognition and that bear clear connections with the eco-social lifestyles of species. However, we also find that the cognitive basis of these skills remain insufficiently studied, and identify new research areas that require further attention in the future. Despite these knowledge gaps and the challenges of working with such large animals, we conclude that vultures may provide fresh insight into our knowledge of the ecology and evolution of cognition.
... 47,48 In contrast, the genus Alouatta has a relatively small brain size compared to Sapajus. 49 The brain size differences have been associated with social factors such as group size as a potential factor that demands high cognition, 50,51 or with diet, proposed by Parker and Gibson 52 and Milton 53 in the "Ecological-Intelligence Hypothesis" that frugivorous primates, such as the Sapajus genus, evolved larger brains due to their higher energetic intake when compared to folivorous primates, such as the genus Alouatta. 49,54 Our data show that the brain is not the only organ larger than expected in Sapajus, and it suggests that this genus might have undergone dwarfism, with a reduction in the body size while maintaining important metabolic organs unaltered. ...
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Background: Comparative studies of kidney morphophysiology in nonhuman primates can help us investigate interspecies differences in growth and aging patterns. Methods: We tested the effect of age and sex in renal morphophysiology in 21 Alouatta caraya and 21 Sapajus apella (age range = 0.5-26 years) by ultrasound, red blood cell (RBC) count, and kidney function tests. Results: A. caraya had greater growth rate and absolute renal volume than S. apella, but the latter showed a greater relative renal volume and RBC count. There was a negative relationship between RBC and age, a positive relationship between creatinine and body mass, and an apparent negative relationship between creatinine and age only in S. apella. Conclusions: Our results indicate that A. caraya has a faster aging mechanism than S. apella, and the higher relative kidney volume in S. apella is suggestive of high metabolic demands in this species.
... Origins or modification of sociality may drive changes in brain tissue investment. Several hypotheses have been advanced to explain changes in neural tissue investment associated with transitions in social behavior, generally referred to as "social brain" hypotheses (Dunbar, 1998). Initially, social brain hypotheses assumed there would be a positive effect of sociality on brain investment, but more recent theoretical treatments (Gronenberg and Riveros, 2009;Lihoreau et al., 2012) and empirical findings (vertebrates: Gonzalez-Voyer et al., 2009;Fedorova et al., 2017;Kverková et al., 2018;social insects: O'Donnell et al., 2015) have called this assumption into question. ...
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The evolution of social systems can place novel selective forces on investment in expensive neural tissue by changing cognitive demands. Previous hypotheses about the impact of sociality on neural investment have received equivocal support when tested across diverse taxonomic groups and social structures. We suggest previous models for social behavior-brain relationships have overlooked important variation in social groups. Social groups vary significantly in structure and function, and the specific attributes of a social group may be more relevant to setting cognitive demands than sociality in general. We have identified intragroup competition, relationship differentiation, information sharing, dominance hierarchies, and task specialization and redundancy as attributes of social behavior which may impact selection for neural investment, and outline how variation in these attributes can result in increased or decreased neural investment with transitions to sociality in different taxa. Finally, we test some of the predictions generated using this framework in a phylogenetic comparison of neural tissue investment in Anelosimus social spiders. Social Anelosimus spiders engage in cooperative prey capture and brood care, which allows for individual redundancy in the completion of these tasks. We hypothesized that in social spider species, the presence of redundancy would reduce selection for individual neural investment relative to subsocial species. We found that social species had significantly decreased investment in the arcuate body, the cognitive center of the spider brain, supporting our predictions. Future comparative tests of brain evolution in social species should account for the special behavioral characteristics that accompany social groups in the subject taxa.
Chapter
Rapid tranquillisation refers to a drug treatment intended to calm down an individual who is supposed to suffer from agitation within a reasonably short time interval. Agitation may be reported by the patient or grossly observable by clinicians (and objectiveness here might be an issue), mainly based on observing activity, which is then compared to a culturally determined range. On one end of the continuum of motor behavioural expression is the extreme sedation and non-response to external stimuli; on the other extreme, there is extreme, uncontrolled agitation that can be assessed through specific rating scales.
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The emergence of the novel coronavirus has put societies under tremendous pressure to instigate massive and rapid behavior change. Throughout history, an effective strategy to facilitate novel behaviors has been to morally condemn those who do not behave in an appropriate way. Accordingly, here, we investigate if complying with the advice of health authorities—for example, to physically distance or vaccinate—has emerged as a moralized issue during the COVID‐19 pandemic. In Study 1, we rely on data (N = 94K) from quota‐sampled rolling cross‐sectional online surveys from eight countries (Denmark, Sweden, Germany, France, Italy, Hungary, the United Kingdom, and the United States). We find that large majorities find it justified to condemn those who do not keep a distance to others in public and around half of respondents blame ordinary citizens for the severity of the pandemic. Furthermore, we identify the most important predictors of condemnation to be behavior change and personal concern, while institutional trust and social distrust also play large but less consistent roles. Study 2 offers a registered replication of our findings on a representative sample of Britons (N = 1.5K). It shows that both moralization and condemnation of both vaccination and general compliance are best predicted by self‐interested considerations.
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Data on the number of adults that an individual contacts at least once a month in a set of British populations yield estimates of network sizes that correspond closely to those of the typical "sympathy group" size in humans. Men and women do not differ in their total network size, but women have more females and more kin in their networks than men do. Kin account for a significantly higher proportion of network members than would be expected by chance. The number of kin in the network increases in proportion to the size of the family; as a result, people from large families have proportionately fewer non-kin in their networks, suggesting that there is either a time constraint or a cognitive constraint on network size. A small inner clique of the network functions as a support group from whom an individual is particularly likely to seek advice or assistance in time of need. Kin do not account for a significantly higher proportion of the support clique than they do for the wider network of regular social contacts for either men or women, but each sex exhibits a strong preference for members of their own sex.
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Group size covaries with relative neocortical volume in nonhuman primates. This regression equation predicts a group size for modern humans very similar to that for hunter-gatherer and traditional horticulturalist societies. Similar group sizes are found in other contemporary and historical societies. Nonhuman primates maintain group cohesion through social grooming; among the Old World monkeys and apes, social grooming time is linearly related to group size. Maintaining stability of human-sized groups by grooming alone would make intolerable time demands. It is therefore suggested (1) that the evolution of large groups in the human lineage depended on developing a more efficient method for time-sharing the processes of social bonding and (2) that language uniquely fulfills this requirement. Data on the size of conversational and other small interacting groups of humans accord with the predicted relative efficiency of conversation compared to grooming as a bonding process. In human conversations about 60% of time is spent gossiping about relationships and personal experiences. Language may accordingly have evolved to allow individuals to learn about the behavioural characteristics of other group members more rapidly than was feasible by direct observation alone.
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This paper examines some of the factors which determine how people know each other and is a preliminary attempt to discover the rules which govern such interactions. An informant-defined experiment was conducted to elicit the information about a person needed by individuals in a small U.S. university town to choose which of their acquaintances was most likely to know that person. We found, as with a previous experiment, that knowledge of the person's location, occupation, hobbies, organizations, age, sex, and marital status was sufficient for this task. These seven facts were then provided for 500 mythical persons spread evenly around the world except that 100 of them supposedly lived in the United States. Forty informants then told us, for each name on the list, whom they knew who was most likely to know that person and why. We found that the data differed little from those of our previous studies in other parts of the United States, suggesting that the instruments is reliable. Of the choices, 86% were friends, 64% male; choices were predominantly made on the basis of the listed person's location or occupation. Factor analysis of similarity matrices based on informant response has allowed categorization for world locations, occupations, and hobbies. Some 23 location categories, 12 ocupation categories, and 13 hobby categories were found. The implications of our findings are discussed in the framework of work in other cultures.
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The tacit assumption that relative enlargement and differentiation of brains reflect a progressive evolutionary trend toward greater intelligence is a major impediment to the study of brain evolution. Theories that purport to establish a linear scale for this presumed correlation between brain size and intelligence are undermined by the absence of an unbiased allometric baseline for estimating differences in encephalization, by the incompatibility of allometric analyses at different taxonomic levels, by the nonlinearity of the criterion of subtraction used to partition the somatic and cognitive components of encephalization, and by the failure to independently demonstrate any cognitive basis for the regularity of brain/body allometry. Analyzing deviations from brain/body allometric trends in terms of encephalization obfuscates the complementarity between brain and body size and ignores selection on body size, which probably determines most deviations. By failing to analyze the effects of allometry at many levels of structure, comparative anatomists have mistaken methodological artifacts for progressive evolutionary trends. Many structural changes, which are assumed to demonstrate progression of brain structure from primitive to advanced forms, are the results of allometric processes. Increased brain size turns out to have some previously unappreciated functional disadvantages.
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In a study of 52 individuals belonging to 35 species or subspecies of passerine birds it was shown that the volume of the hippocampal complex relative to brain and body size is significantly larger in species that store food than in species that do not. Retrieval of stored food relies on an accurate and long-lasting spatial memory, and hippocampal damage disrupts memory for storage sites. The results suggest, therefore, that food-storing species of passerines have an enlarged hippocampal complex as a specialization associated with the use of a specialized memory capacity. Other life-history variables were examined and found not to be correlated with hippocampal volume.
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This paper examines relationships between brain size (relative to body size) and differences in ecology and behavior within the order Carnivora. After removing the effects of body size (either body weight or head and body length) significant differences in brain size exist among families. Variation in relative brain size across the order and comparative brain size within families might relate to differences in diet (carnivores and omnivores have larger brain sizes than insectivores) and breeding group type. These findings are discussed and compared with those found in small mammals (rodents, insectivores, lagomorphs), primates and bats.
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Two explanations for species differences in neonatal brain size in eutherian mammals relate the size of the brain at birth to maternal metabolic rate. Martin (1981, 1983) argued that maternal basal metabolic rate puts an upper bound on the mother's ability to supply energy to the fetus, thereby limiting neonatal brain size. Hofman (1983) proposed that gestation length in mammals is constrained by maternal metabolic rate, implying an indirect constraint on neonatal brain size. Since individuals of precocial species have much larger neonatal brain sizes and are gestated longer for a given maternal body size than individuals of altricial species, Martin's and Hofman's ideas also require that mothers of precocial offspring have higher metabolic rates for their body sizes than mothers of altricial offspring. Data on 116 mammal species from 13 orders show that neither neonatal brain size nor gestation length is correlated with maternal metabolic rate when maternal body-size effects are removed. For a given maternal size, there is no difference in metabolic rates between precocial and altricial species, despite a two-fold difference between them in average neonatal brain size. However, neonatal brain size is strongly correlated with gestation length and litter size, independently of maternal size and metabolic rate. Analyses conducted within orders replicated the findings for gestation length and suggested that neonatal brain size may be at best only weakly related to metabolic rate. Differences in neonatal brain size appear to have evolved primarily with species differences in gestation length and litter size but not with differences in metabolic rate; large-brained offspring are typically produced from litters of one that have been gestated for a long time relative to maternal size. We conclude that species differences in relative neonatal brain size reflect different life-history tactics rather than constraints imposed by metabolic rate.
Article
In this paper we propose a typology for classifying object manipulation and tool use. We then classify tool use as context specific or intelligent tool use on the basis of criteria drawn from Piaget's Sensorimotor Intelligence Series in human infants. In an extension of Hamilton's hypothesis we argue that intelligent tool use and tertiary sensorimotor intelligence in cebus monkeys and great apes is an adaptation for feeding on a variety of seasonally limited embedded food sources, while context specific tool use is an adaptation for feeding on one class of embedded food sources. We also argue that the evolution of specific object manipulation schemata must be considered separately from the evolution of intelligence.
Article
The hypothesis that intelligence is an adaptation to deal with the complexity of living in semi-permanent groups of conspecifics, a situation that involves the potentially tricky balance of competition and cooperation with the same individuals, has been influential in recent theorizing about human mental evolution. It is important to distinguish among distinct versions of this general idea, for they predict different cognitive consequences and apply to different species of animal. Empirical support is strong in primates for links between (i) social complexity based on evolved tactics that require a good memory for socially relevant information, (ii) neocortical enlargement, and (iii) size of social groupings. However, the evolution of computational thought and the ability to understand other individuals' intentions are not well explained as products of selection for Machiavellian intelligence. Quite different explanations may therefore be required for increases in intelligence that occurred at different times in human ancestry.
Article
The abstract for this document is available on CSA Illumina.To view the Abstract, click the Abstract button above the document title.
Article
Primates use social grooming to service coalitions and it has been suggested that these directly affect the fitness of their members by allowing them to reduce the intrinsic costs associated with living in large groups. We tested two hypotheses about the size of grooming cliques that derive from this suggestion: (1) that grooming clique size should correlate with relative neocortex size and (2) that the size of grooming cliques should be proportional to the size of the groups they have to support. Both predictions were confirmed, although we show that, in respect of neocortex size, there are as many as four statistically distinct grades within the primates (including humans). Analysis of the patterns of grooming among males and females suggested that large primate social groups often consist of a set of smaller female subgroups (in some cases, matrilinearly based coalitions) that are linked by individual males. This may be because males insert themselves into the interstices between weakly bonded female subgroups rather than because they actually hold these subunits together.
Article
In this paper, the analysis of the factors influencing the evolution of neocortex size in primates given in Dunbar (1992) is extended in three specific ways. (1) An independent test is undertaken of the hypothesis that group size is a function of relative neocortex size in primates by using estimates of neocortex size to predict group size for those species that were not involved in the original analysis. The results confirm the results of the earlier analysis. (2) A more satisfactory test is attempted of the alternative hypothesis that species which differ in the degree of extractive foraging also differ in relative neocortex size. This particular version of the hypothesis is rejected. (3) These results are used to identify the "cognitive" group size for those species of baboons that live in multi-layered social systems.
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Our book examines the mechanisms that underlie social behavior and communication in East African vervet monkeys. Our goal is to describe the sophistication of primate intelligence and to probe its limits. We suggest that vervets and other primates make good primatologists. They observe social interactions, recognize the relations that exist among others, and classify relationships into types. Monkeys also use sounds to represent features of their environment and compare different vocalizations according to their meaning. However, while monkeys may use abstract concepts and have motives, beliefs, and desires, their mental states are apparently not accessible: they do not know what they know. In addition, monkeys seem unable to attribute mental states to others: they lack a "theory of mind." Their inability to examine their own mental states or to attribute mental states to others severely constrains their ability to transmit information or to deceive one another. It also limits the extent to which their vocalizations can be called semantic. Finally, the skills that monkeys exhibilt in social behavior are apparently domain specific. For reasons that are presently unclear, vervets exhibit adaptive specializations in social interactions that are not extended to their interactions with other species (although they should be).
Article
The social brain hypothesis predicts that species with relatively larger neocortices should exhibit more complex social strategies than those with smaller neocortices. We test this prediction using data on the correlation between male rank and mating success for polygamous primates. This correlation is negatively related to neocortex size, as would be predicted if males of species with large neocortices are more effective at exploiting social opportunities to undermine the dominant male's power-based monopolisation of peri-ovulatory females than are those with smaller neocortices. This effect is shown to be independent of the influence of male cohort size.
Article
reviews evidence that complex patterns of alliance make primate contests more intellectually demanding than those of other animals and, in arguing that this has led to primates' greater relative brain size, challenges students of non-primates to produce better comparative data (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Tactical deception occurs when an individual is able to use an “honest” act from his normal repertoire in a different context to mislead familiar individuals. Although primates have a reputation for social skill, most primate groups are so intimate that any deception is likely to be subtle and infrequent. Published records are sparse and often anecdotal. We have solicited new records from many primatologists and searched for repeating patterns. This has revealed several different forms of deceptive tactic, which we classify in terms of the function they perform. For each class, we sketch the features of another individual's state of mind that an individual acting with deceptive intent must be able to represent, thus acting as a “natural psychologist.” Our analysis will sharpen attention to apparent taxonomic differences. Before these findings can be generalized, however, behavioral scientists must agree on some fundamental methodological and theoretical questions in the study of the evolution of social cognition.
Article
Mean body weights of baboons differ considerably between populations for both males and females. This paper examines possible environmental causes of these differences. Mean annual rainfall and mean annual temperature are shown to be the two main factors responsible. Mean body weights for both sexes are a quadratic function of rainfall. Possible reasons why this might be so are examined.
Article
Fifty-five million years ago, a furry, hoofed mammal about the size of a dog ventured into the shallow brackish remnant of the Tethys Sea and set its descendants on a path that would lead to their complete abandonment of the land. These early ancestors of cetaceans (dolphins, porpoises, and whales) thereafter set on an evolutionary course that is arguably the most unusual of any mammal that ever lived. Primates and cetaceans, because of their adaptation to exclusively different physical environments, have had essentially nothing to do with each other throughout their evolution as distinct orders. In fact, the closest phylogenetic relatives of cetaceans are even-toed ungulates.
Article
The ability to understand and conceptualize the mental processes of other people is considered to play a vital role in social interactions. Deficits in this area, sometimes known as theory-of-mind (ToM) deficits, have been identified as playing a possible causal role in autism, Asperger's syndrome and schizophrenic disorders, particularly paranoia. Paranoia has also been associated with an abnormal attributional style, an observation that suggests that ToM and attributional processes may be related phenomena. This paper describes a study examining the relationship between attributional processes and ToM deficits. Seventy-seven undergraduate participants completed a ToM task and forty-six also completed the Internal, Personal and Situational Attributions Questionnaire (IPSAQ). ToM deficits were associated with an increased tendency to identify other individuals as responsible for negative social situations. The implications of the observed relationship between attributions and ToM deficits are discussed.
Article
Recent hypotheses that variation in brain size among birds and mammals result from differences in metabolic allocation during ontogeny are tested. Indices of embryonic and post-embryonic brain growth are defined. Precocial birds and mammals have high embryonic brain growth indices which are compensated for by low post-embryonic indices (with the exception of Homo supiens). In contrast, altricial birds and mammals have low embryonic and high post-embryonic indices. Altricial birds have relatively small brains at hatching and develop relatively large brains as adults, but among mammals there is no equivalent correlation between variation in adult relative brain sizes and state of neonatal development. Compensatory brain development in both birds and mammals is associated with compensatory parental metabolic allocation. In comparison with altricial development, precocial development is characterized by higher levels of brain growth and parental metabolic allocation prior to hatching or birth and lower levels subsequently. Differences between degrees of postnatal investment by the parents in the young of precocial birds versus precocial mammals may result in the different patterns of adult brain size associated with precociality versus altriciality in the two groups. The allometric exponent scaling brain on body size differs among taxonomic levels in birds. The exponent is higher for some parts of the brain than others, irrespective of taxonomic level. Unlike mammals, the exponents for birds do not show a general increase with taxonomic level. These pattcrns call into question recent interpretations of the allometric exponent in birds. and the reason for changes in exponent with taxonomic level.
Article
The relationships between the relative size of the neocortex and differences in social structures were examined in prosimians and anthropoids. The relative size of the neocortex (RSN) of a given congeneric group in each superfamily of primates was measured based on the allometric relationships between neocortical volume and brain weight for each superfamily, to control phylogenetic affinity and the effects of brain size. In prosimians, “troop-making” congeneric groups (N=3) revealed a significantly larger RSN than solitary groups (N=6), and there was a significant, positive correlation between RSN and troop size. In the case of anthropoids, polygynous/frugivorous groups (N=5) revealed a significantly larger RSN than monogynous/frugivorous groups (N=8). Furthermore, a significant, positive correlation between RSN and troop size was found for frugivorous congeneric groups of the Ceboidea. These results suggest that neocortical development is associated with differences in social structure among primates.
Article
Two general kinds of theory (one ecological and one social) have been advanced to explain the fact that primates have larger brains and greater congnitive abilities than other animals. Data on neocortex volume, group size and a number of behavioural ecology variables are used to test between the various theories. Group size is found to be a function of relative neocortical volume, but the ecological variables are not. This is interpreted as evidence in favour of the social intellect theory and against the ecological theories. It is suggested that the number of neocortical neurons limits the organism's information-processing capacity and that this then limits the number of relationships that an individual can monitor simultaneously. When a group's size exceeds this limit, it becomes unstable and begins to fragment. This then places an upper limit on the size of groups which any given species can maintain as cohesive social units through time. The data suggest that the information overload occurs in terms of the structure of relationships within tightly bonded grooming cliques rather than in terms of the total number of dyads within the group as a whole that an individual has to monitor. It thus appears that, among primates, large groups are created by welding together sets of smaller grooming cliques. One implication of these results is that, since the actual group size will be determined by the ecological characteristics of the habitat in any given case, species will only be able to invade habitats that require larger groups than their current limit if they evolve larger neocortices.
Article
Understanding of second-order belief structures by 5- and 10-year-old children was assessed in acted stories in which two characters (John and Mary) were independently informed about an object's (ice-cream van's) unexpected transfer to a new location. Hence both John and Mary knew where the van was but there was a mistake in John's second-order belief about Mary's belief: “John thinks Mary thinks the van is still at the old place”. Children's understanding of this second-order belief was tested by asking “Where does John think Mary will go for ice cream?” Correct answers could only be given if John's second-order belief was represented, since all shortcut reasoning based on first-order beliefs would have led to the wrong answer. Results suggested unexpected early competence around the age of 6 and 7 years, shown under optimal conditions when inference of second-order beliefs was prompted.