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The Social Brain Hypothesis
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.
... These close relationships are associated with high emotional intensity and they are surrounded by a larger number of weaker ties. The emergence of this characteristic structural pattern has been associated with constraints on maintaining social relationships, which include limited information processing capacity 11 , social cognition [12][13][14] , and time availability [15][16][17] . ...
... The cumulative advantage mechanism that drives the dispersion of tie strength can be thought to effectively result from people putting more emphasis on their closest relationships, which arise in part due to similarities in any number of sociodemographic, behavioral, and intrapersonal characteristics 59 . Generally, the heterogeneity of tie strengths in ego networks has been attributed to cognitive, temporal, and other constraints [11][12][13][15][16][17] , and different personality traits 60,61 and their relative stability have been proposed as one possible reason for the persistent individual variation in this heterogeneity 20 . ...
... One possibility is that our brain is simply wired to consistently shape our social networks in similar ways, independent of the specific medium of communication 13,63 . Alternatively, the reason may lie in the mechanisms of tie strength reinforcement: cumulative advantage may arise, e.g., because we have already participated in an online conversation with someone and it is easier to continue interacting with the same alter. ...
Tie strengths in social networks are heterogeneous, with strong and weak ties playing different roles at the network and individual levels. Egocentric networks, networks of relationships around an individual, exhibit few strong ties and more weaker ties, as evidenced by electronic communication records. Mobile phone data has also revealed persistent individual differences within this pattern. However, the generality and driving mechanisms of social tie strength heterogeneity remain unclear. Here, we study tie strengths in egocentric networks across multiple datasets of interactions between millions of people during months to years. We find universality in tie strength distributions and their individual-level variation across communication modes, even in channels not reflecting offline social relationships. Via a simple model of egocentric network evolution, we show that the observed universality arises from the competition between cumulative advantage and random choice, two tie reinforcement mechanisms whose balance determines the diversity of tie strengths. Our results provide insight into the driving mechanisms of tie strength heterogeneity in social networks and have implications for the understanding of social network structure and individual behavior.
... Several hypotheses have been proposed for the expected phylogenetic distribution of reliance on social information. The first and most popular hypothesis (social intelligence) is that social species evolve to take advantage of the greater amount of social information available to them and are thus expected to rely more on social information than solitary species [8,9]. A second non-mutually exclusive hypothesis ( predation risk) suggests species more at risk for predation rely more on social information because the costs of using individual information are increased [5]. ...
... Social interaction has been suggested to drive the evolution of intelligence and brain size [8,9], with supporting evidence coming from a comparative primate study associating group size with brain size [8]. However, this relationship is often not supported, leading to calls for more nuanced investigation of the relationship between sociality and social intelligence (e.g. ...
... Social interaction has been suggested to drive the evolution of intelligence and brain size [8,9], with supporting evidence coming from a comparative primate study associating group size with brain size [8]. However, this relationship is often not supported, leading to calls for more nuanced investigation of the relationship between sociality and social intelligence (e.g. ...
Individuals can reduce sampling costs and increase foraging efficiency by using information provided by others. One simple form of social information use is delayed local enhancement or increased interest in a location because of the past presence of others. We tested for delayed local enhancement in two ecomorphs of stickleback fish, benthic and limnetic, from three different lakes with putative independent evolutionary origins. Two of these lakes have reproductively isolated ecomorphs (species-pairs), whereas in the third, a previously intact species-pair recently collapsed into a hybrid swarm. Benthic fish in both intact species-pair lakes were more likely to exhibit delayed local enhancement despite being more solitary than limnetic fish. Their behaviour and morphology suggest their current perceived risk and past evolutionary pressure from predation did not drive this difference. In the hybrid swarm lake, we found a reversal in patterns of social information use, with limnetic-looking fish showing delayed local enhancement rather than benthic-looking fish. Together, our results strongly support parallel differentiation of social learning differences in recently evolved fish species, although hybridization can apparently erode and possibly even reverse these differences.
... It does not correlate with any feature marked by Spanish law. Rather, its proximity to Dunbar's number (an empirical cognitive limit to the number of relationships that animals can have [13][14][15][16][17][18][19][20][21]) suggests an organic emergence of social complexity. ...
... (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) finite [14,18]. Dunbar's number was introduced as a speculative, soft upper-bound to the number of meaningful relationships that individuals can sustain. ...
... We speculate that̂ † corresponds to an organic build-up of social complexity as communities cross a size threshold. We suggest that this size threshold is associated to Dunbar's number, a soft limit proposed for the maximal amount of meaningful relationships that humans (and other animals) can sustain [13][14][15][16][17][18]20,21]. We argue that this cognitive limit to relationships imposes a constrain on growing social networks that forces them to become more complex -presenting holes, mesoscale communities dictated by affinity or proximity, etc. ...
How do societies become more complex? Are there specific scales at which they are reorganized into emergent entities? Social dynamics are shaped by each person's actions, as well as by collective trends that emerge when individuals are brought together. Features like population size, polarization, cohesion, or hierarchy add nuance and complexity to social structure, and might be present, or not, for societies of different sizes. Here we show that, while societal complexity increases monotonically with population, there are specific scales at which complexity builds up faster-one of them is close to Dunbar's number (an estimation of the number of meaningful relationships that individuals can sustain). We have observed this by measuring, as a probe across populations of varied sizes, the sociolinguistic process that has unfolded over decades within the Spanish region of Galicia. For this, we have developed a methodological tool (social complexity spectrum), inspired by theoretical considerations about dynamics on complex networks, that could be applied in further study cases. Teaser: Changes in collective human behavior triggered by a critical population size found through sociolinguistic analysis
... Наиболее популярна гипотеза Дунбара, согласно которой движущей силой эволюции мозга у гоминидов было увеличение размеров социальной группы (Dunbar, 1998). Понятно, что выживать группой легче, чем поодиночке, но жизнь в группе тоже не проста, так как требует соблюдения баланса между эгоистическими стремлениями каждого индивида и сохранением гармонии в группе. ...
... Принимая в расчет явную социальную направленность морали, а также то, что, по наиболее популярной в настоящее время теории, движущей силой эволюции мозга у гоминидов были именно социальные факторы (Dunbar, 1998), можно было бы ожидать, что мораль должна иметь явное и значительное представительство в мозге человека, так как способность интуитивно различать морально приемлемые и неприемлемые поступки представляется более важной для поддержания гармонии в социальной группе, чем, например, способность к абстрактному мышлению. Существующие эмпирические данные показывают, однако, что в мозге нет «морального центра» и «моральный мозг» включает области, чьи изначальные функции не имеют ничего общего с моралью (Verplaetse et al., 2009). ...
... Что ведет к появлению все более изощренных изобретений, открытий и инноваций? По своим интеллектуальным способностям человек превосходит остальные биологические виды на Земле, и в главе, посвященной эволюции человека, мы видели, что согласно наиболее популярным в настоящее время теориям, эти способности появились в процессе поиска путей разрешения социальных проблем (Dunbar, 1998). Эти теории подчеркивают важность социальных процессов в эволюции человека как биологического вида, но не объясняют почему эволюция шла именно по этому пути и в эту сторону. ...
What is the meaning of life? What is the nature of the human mind, love, morality? All of these questions tend to be answered and explained in "natural science" terms. Life arose out of inanimate nature by random physical and chemical factors and one should hardly look for any sense in it; man is the product of natural selection and reason, love and morality, are the result of chemical and electrical processes in the brain. Since these questions are among the most important for human beings, due to the unquestionable authority of the natural sciences, the proposed answers can and already do have a major impact on all areas of human life, from economics and politics to mental health and the subjective well-being of the individual. Does this perception of the world and one's place in it make one happy? Sociological studies clearly say no. Adherents of this worldview, however, argue that no matter how unpleasant it may seem, one should have the courage to accept it, because it is consistent with the scientific evidence. But is this true? Does the modern scientific picture of the world really allow for all these far-reaching conclusions? People who are professionally involved in science know that it almost never provides answers to worldview questions. All empirical facts and scientific theories can be interpreted in different ways and the choice of one interpretation or another is largely determined by one's worldview position, not vice versa. Although the book is called "Worldview Problems of Neuroscience", and most of it is indeed devoted to neuroscientific problems and their philosophical interpretation, it deals with a wider range of questions, which form the basis of the worldview of most modern people. Author tries to understand whether the reductionist materialistic worldview that dominates today, especially in the neurosciences, is really capable of plausibly explaining the current evidence about the nature of the relationship between mental processes and the physical world. The book concludes by outlining modern philosophical positions alternative to orthodox physicalism and tries to summarize them in a unified system.
... These close relationships are associated with high emotional intensity and they are surrounded by a larger number of weaker ties. The emergence of this characteristic structural pattern has been associated with constraints on maintaining social relationships, which include limited information processing capacity [11], social cognition [12][13][14], and time availability [15][16][17]. ...
... The cumulative advantage mechanism that drives the dispersion of tie strength can be simply thought to result from people putting more emphasis on their closest relationships. Generally, the heterogeneity of tie strengths in ego networks has been attributed to cognitive, temporal, and other constraints [11][12][13][15][16][17], and different personality traits [61,62] and their relative stability have been proposed as one possible reason for the persistent individual variation in this heterogeneity [20]. ...
... One possibility is that our brain is simply wired to consistently shape our social networks in similar ways, independent of the specific medium of communication [13,64]. Alternatively, the reason may lie in the mechanisms of tie strength reinforcement: cumulative advantage may arise, e.g., because we have already participated in an online conversation with someone and it is easier to continue interacting with the same alter. ...
Tie strengths in social networks are heterogeneous, with strong and weak ties playing different roles at both the network and the individual level. Egocentric networks, networks of relationships around a focal individual, exhibit a small number of strong ties and a larger number of weaker ties, a pattern that is evident in electronic communication records, such as mobile phone calls. Mobile phone data has also revealed persistent individual differences within this pattern. However, the generality and the driving mechanisms of this tie strength heterogeneity remain unclear. Here, we study tie strengths in egocentric networks across multiple datasets containing records of interactions between millions of people over time periods ranging from months to years. Our findings reveal a remarkable universality in the distribution of tie strengths and their individual-level variation across different modes of communication, even in channels that may not reflect offline social relationships. With the help of an analytically tractable model of egocentric network evolution, we show that the observed universality can be attributed to the competition between cumulative advantage and random choice, two general mechanisms of tie reinforcement whose balance determines the amount of heterogeneity in tie strengths. Our results provide new insights into the driving mechanisms of tie strength heterogeneity in social networks and have implications for the understanding of social network structure and individual behavior.
... It does not correlate with any feature marked by Spanish law. Rather, its proximity to Dunbar's number (an empirical-yet debated [13][14][15]-cognitive limit to the number of relationships that animals can have [16][17][18][19][20][21][22][23]) suggests an organic emergence of social complexity. ...
... We speculate that our marked dip atθ † u = 183 might reflect an organic emergence of hierarchy that might take place as human groups become larger than Dunbar's number. The underlying hypothesis here is that the cognitive effort that people can devote to their peers is finite [17,21]. Dunbar's number was introduced as a speculative, soft upper-bound to the number of meaningful relationships that individuals can sustain. ...
... We speculate thatθ † u corresponds to an organic buildup of social complexity as communities cross a size threshold. We suggest that this size threshold is associated to Dunbar's number, a soft limit proposed for the maximal amount of meaningful relationships that humans (and other animals) can sustain [16][17][18][19][20][21][22][23]). We argue that this cognitive limit to relationships imposes a constrain on growing social networks that forces them to become more complex-presenting holes, mesoscale communities dictated by affinity or proximity, etc. ...
Social dynamics are shaped by each person's actions, as well as by collective trends that emerge when individuals are brought together. These latter kind of influences escape anyone's control. They are, instead, dominated by aggregate societal properties such as size, polarization, cohesion, or hierarchy. Such features add nuance and complexity to social structure, and might be present, or not, for societies of different sizes. How do societies become more complex? Are there specific scales at which they are reorganized into emergent entities? In this paper we introduce the {\em social complexity spectrum}, a methodological tool, inspired by theoretical considerations about dynamics on complex networks, that addresses these questions empirically. We use as a probe a sociolinguistic process that has unfolded over decades within the north-western Spanish region of Galicia, across populations of varied sizes. We estimate how societal complexity increases monotonously with population size; and how specific scales stand out, at which complexity would build up faster. These scales are noted as dips in our spectra, similarly to missing wavelengths in light spectroscopy. Also, `red-' and `blue-shifts' take place as the general population shifted from more rural to more urban settings. These shifts help us sharpen our observations. Besides specific results around social complexity build-up, our work introduces a powerful tool to be applied in further study cases.
... Our understanding of the impact of group living and its complexities on brain evolution remains incomplete after extensive theoretical development and empirical research. The social brain hypothesis states that increased requirements to monitor complex relationships in large groups selected for larger brains capable of advanced behavioral calculus to promote fitness [2,3]. This begs the broader question of the role of brain size in behavioral performance [4,••5] and the application of the social brain hypothesis to eusocial insects, which have miniature brains, has indeed been explored ( [6][7][8], and references therein). ...
... Complexity in eusocial insect-colony organization may involve either selection for smaller, neurally differentiated worker brains [8,[41][42][43], larger brains [44], or allometrically large brain centers [13] that may metabolically offset costs of increased size [45]. The social brain hypothesis [2] is broadly supported by studies of brain evolution in the ant genus Cataglyphis: workers of species that form large colonies have larger brains [44]. However, the social brain hypothesis does not imply the existence of an emergent 'social group brain' and the Cataglyphis comparative study does not involve reproductive competition, but rather suggests a role for colony size, which affects the number and complexity of worker interactions. ...
... Predictions concerning brain size and structure, primarily in workers, are inferred from task-associated behavioral and/or cognitive demands. The influence of social conflict is presented as the social brain hypothesis [2] for ant species characterized by reproductive competition. ...
Brain evolution is hypothesized to be driven by requirements to adaptively respond to environmental cues and social signals. Diverse models describe how sociality may have influenced eusocial insect brain evolution but specific impacts of social organization and other selective forces on brain architecture have been difficult to distinguish. Here we evaluate predictions derived from and/or inferences made by models of social organization concerning the effects of individual and collective behavior on brain size, structure, and function using results of neuroanatomical and genomic studies. In contrast to the predictions of some models, we find that worker brains in socially complex species have great behavioral and cognitive capacity. We also find that colony size, the evolution of worker physical castes and task specialization affect brain size and mosaicism, supporting the idea that sensory, processing, and motor requirements for behavioral performance select for adaptive allometries of functionally specialized brain centers. We review available transcriptomic and comparative genomic studies seeking to elucidate the molecular pathways functionally associated with social life and the genetic changes that occurred during the evolution of social complexity. We discuss ways forward, using comparative neuroanatomy, transcriptomics, and comparative genomics, to distinguish among multiple alternative explanations for the relationship between the evolution of neural systems and social complexity.
... hypotheses for the emergence of intelligent behavior. The social-intelligence hypothesis is the dominant view and proposes that social complexity drives cognitive evolution (Byrne & Whiten, 1988;Dunbar, 1998;Moll & Tomasello, 2007;van Schaik & Burkart, 2011). Various social challenges-such as maintaining multiple relationships in a large complex group, outcompeting other individuals, and cooperating or learning from others-have all been proposed as evolutionary drivers of larger brains and enhanced cognition (Dunbar, 1998;Byrne & Whiten, 1988;Moll & Tomasello, 2007;van Schaik & Burkart, 2011). ...
... The social-intelligence hypothesis is the dominant view and proposes that social complexity drives cognitive evolution (Byrne & Whiten, 1988;Dunbar, 1998;Moll & Tomasello, 2007;van Schaik & Burkart, 2011). Various social challenges-such as maintaining multiple relationships in a large complex group, outcompeting other individuals, and cooperating or learning from others-have all been proposed as evolutionary drivers of larger brains and enhanced cognition (Dunbar, 1998;Byrne & Whiten, 1988;Moll & Tomasello, 2007;van Schaik & Burkart, 2011). In contrast, the ecological-intelligence hypothesis posits that ecological challenges spur cognitive evolution. ...
... However, prior tests of the social-and ecologicalintelligence hypotheses have been limited in several respects. First, a dominant approach has been to use brain size, rather than direct assessments of cognition, as a proxy for cognition (DeCasien et al., 2017;Dunbar, 1998), but broad neuroanatomical measures are only an approximate index for specific cognitive traits (Logan et al., 2018). Direct tests of cognition have heavily focused on individual species, or pairs of species, which limits evolutionary inferences (e.g., Rosati, 2017b;Rosati et al., 2007;Rosati & Hare, 2012;Wobber et al., 2010). ...
Cognitive control, or executive function, is a key feature of human cognition, allowing individuals to plan, acquire new information, or adopt new strategies when the circumstances change. Yet it is unclear which factors promote the evolution of more sophisticated executive-function abilities such as those possessed by humans. Examining cognitive control in nonhuman primates, our closest relatives, can help to identify these evolutionary processes. Here, we developed a novel battery to experimentally measure multiple aspects of cognitive control in primates: temporal discounting, motor inhibition, short-term memory, reversal learning, novelty responses, and persistence. We tested lemur species with targeted, independent variation in both ecological and social features (ruffed lemurs, Coquerel’s sifakas, ring-tailed lemurs, and mongoose lemurs; N = 39) and found that ecological rather than social characteristics best predicted patterns of cognitive control across these species. This highlights the importance of integrating cognitive data with species’ natural history to understand the origins of complex cognition.
... 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). ...
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
... 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. ...
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.
... Abstract knowledge emerged, indeed, as the result of intellectual agreements on shared meanings attributed to experiences and validated by communities (see Gilead et al., 2020). Although the process of conflating different experiences in a single symbol characterizes all concepts and words (e.g., Deacon, 1998;Dunbar, 1998), the heterogeneity of experiences that ACs evoke makes people more uncertain of their meaning and renders the input and interaction with others particularly crucial. During their use, we might need to rely on other people to understand the meaning of words on which we are uncertain or to negotiate their meaning Mazzuca & Santarelli, 2022). ...
... During their use, we might need to rely on other people to understand the meaning of words on which we are uncertain or to negotiate their meaning Mazzuca & Santarelli, 2022). Consequently, the full development of abstract representations might rely upon successful linguistic exchanges among conspecifics (see Dunbar, 1998). ACs would not only be the "glue" holding together scattered and heterogeneous information (see the notion of situational systematicity in Davis et al., 2020), but they would also represent the "social glue" providing a common reference of knowledge within societies Borghi & Tummolini, 2020;Mazzuca et al., 2021;Mazzuca & Santarelli, 2022). ...
domains of knowledge may have social origins. However, whether abstract concepts (ACs) may also differentially affect communicative interaction and conversation has not been explored. Here, we studied ACs’ communicative functions by collecting in an Italian and an English sample, ratings for concrete concept (CC) and ACs related to three main dimensions: communicative/pragmatic [i.e., Openness to Negotiation (ON), Easiness to Start a Conversation (ESC)], semantic/metacognitive [i.e., Social Metacognition (SM) – perceived need of others, Word Confidence (WC), Contextual Availability (CA)], and emotional–experiential (i.e., Pleasantness, Valence, Familiarity). Overall, Italian participants judged it was easier to start a conversation, the more pleasant, familiar, and positively valenced were rated the concepts. Crucially, at lower values of the emotional–experiential component (i.e., Familiarity in the Italian sample, also Pleasantness and Valence in an English sample), there was an advantage of ACs over CCs in the ESC. Moreover, in the Italian sample, participants rated ACs higher on SM, ON, and lower on WC and CA. Notably, in both the Italian and English sample, ACs with higher ratings on the ESC dimension belonged to the Self-Sociality subcluster. The results offer new insights into the pragmatic aspects linked to ACs’ use.
... However, even if the environment provided the means for extracting sufficiently high amounts of energy, we still face the question of how the same environment selected for expansion to occur. We address this question by building on the "social brain hypothesis" literature (Dunbar 1998(Dunbar , 2003(Dunbar , 2009, which argues that evolutionarily expanded regions of the human brain appear to subserve key functions for successful social interaction, and we outline how this may have provided a path to "pay the energetic bill" for these regions' metabolic expenditure. 14 ...
... Building on this intriguing overlap, the "social brain hypothesis" 15 posits that the necessity to navigate complex social dynamics within the group and with outgroup conspecifics (Ashton and others 2020) would have exerted evolutionary pressures that favored the ability to interpret, predict, leverage, and manipulate others' behavior-and the consequent growth of associated cortical structures, according to the theory (Byrne and Whiten 1989;Dunbar 1998Dunbar , 2003Dunbar , 2009Humphrey 1976;Whiten and Byrne 1997). Dealing with such interactions extends the range and diversity of cognitive abilities that are required from a given individual, thereby contributing to the development of progressively more domain-general and flexible cognitive capacities (Humphrey 1976). ...
Scientific theories on the functioning and dysfunction of the human brain require an understanding of its development—before and after birth and through maturation to adulthood—and its evolution. Here we bring together several accounts of human brain evolution by focusing on the central role of oxygen and brain metabolism. We argue that evolutionary expansion of human transmodal association cortices exceeded the capacity of oxygen delivery by the vascular system, which led these brain tissues to rely on nonoxidative glycolysis for additional energy supply. We draw a link between the resulting lower oxygen tension and its effect on cytoarchitecture, which we posit as a key driver of genetic developmental programs for the human brain—favoring lower intracortical myelination and the presence of biosynthetic materials for synapse turnover. Across biological and temporal scales, this protracted capacity for neural plasticity sets the conditions for cognitive flexibility and ongoing learning, supporting complex group dynamics and intergenerational learning that in turn enabled improved nutrition to fuel the metabolic costs of further cortical expansion. Our proposed model delineates explicit mechanistic links among metabolism, molecular and cellular brain heterogeneity, and behavior, which may lead toward a clearer understanding of brain development and its disorders.
... Neuroanatomical comparisons can also inform researchers about how animals transitioned from solitary to social life. The "social brain hypothesis" posits that increasing levels of sociality are associated with larger brains to support the processing of more social information (Dunbar, 1998). However, the distributed cognition of highly integrated groups with division of labor may alleviate the cognitive load on the individuals, and potentially reduce their neural requirements (Gronenberg and Riveros, 2009). ...
... The studies in this collection seek to understand how behavioral and neural characteristics enable individuals to engage in social behaviors and how social organization, or collective behavior, may alter individual cognition. They nicely illustrate how research on the evolution of brains and cognition has recently moved from broad correlations between brain sizes and social organization (Dujardin, 1850;Dunbar, 1998) to more detailed considerations of the neuroethology of specific socio-cognitive behaviors (Lihoreau et al., 2012;Godfrey and Gronenberg, 2019). Future research will have to account for variation in cognition across group members (Naug and Tait) and life history strategies that characterize the group. ...
... hipotezą mózgu społecznego (ang. social brain hypothesis), wzrost wielkości owego narządu -szczególnie obszaru kory nowej (Dunbar, 1998) -oraz towarzyszący mu rozwój intelektu mogły stanowić odpowiedź na wyzwania związane z funkcjonowaniem hominidów w ramach rozbudowanych grup społecznych (Przybysz, 2014). Przeżycie naszych przodków w znacznym stopniu zależało bowiem od skutecznej współpracy i porozumiewania się, a także współzawodnictwa z przedstawicielami własnego gatunku (Bjorklund, Bering, 2009), co z kolei wymagało wykształcenia umiejętności wykonywania złożonych operacji mentalnych, takich jak odczytywanie intencji innych osobników, przewidywanie dalekosiężnych konsekwencji ich działań czy poszukiwanie optymalnych rozwiązań konfliktów (Foley, 2001). ...
... Narząd ten, choć jego waga stanowi zaledwie ok. 2-3 procent masy ciała człowieka, wykorzystuje mniej więcej jedną piątą energii pozyskiwanej przez organizm (Dunbar, 1998;Foley, 2001). Rezultaty badań z użyciem pozytonowej tomografii emisyjnej wskazują, iż zapotrzebowanie na glukozę, cukier będący podstawowym "paliwem" tkanki mózgowej (Nęcka, 2003), wyraźnie nasila się podczas wykonywania angażujących poznawczo zadań (np.: rozwiązywania Testu Matryc Ravena w wersji dla zaawansowanych, nauki grania w Tetrisa), przy czym efekt ów jest słabszy w przypadku osób uzyskujących lepsze wyniki w testach inteligencji ogólnej (Haier i in., 1988,9). ...
PL: Niniejsza praca dotyczy wpływu stereotypów na funkcjonowanie poznawcze człowieka. Za jej główny cel obrano ustalenie, czy poziom zdolności metapoznawczych może regulować związek między zjawiskiem zagrożenia stereotypem i efektem stereotype boost a wynikami uzyskiwanymi w zadaniach poznawczych.
Przeprowadzona procedura badawcza składała się z dwóch etapów. W pierwszym z nich uczestnicy wypełniali Skalę Metapoznawczego Ja (Brycz i in., 2019) oraz Test Matryc Hagen (Heydasch, 2014). Wyniki uzyskane w tym ostatnim pozwoliły podzielić ich na sześć grup, ujednoliconych pod względem średniego poziomu zdolności intelektualnych. Do grup A, C i E przypisano kobiety, natomiast do grup B, D i F – mężczyzn. Podczas drugiego etapu badania zastosowano manipulację polegającą na przedstawieniu uczestnikom zadania, z którym mieli się zmierzyć, jako związanego z umiejętnościami stereotypowo męskimi (grupy C i D) albo stereotypowo kobiecymi (grupy E i F). Osoby przydzielone do grup kontrolnych (A i B) czytały instrukcję neutralną z uwagi na płeć.
Wykonane analizy wykazały, że wzbudzanie stereotypów związanych z płcią istotnie różnicowało wyniki pozyskiwane w zadaniu poznawczym, jakim był Zrewidowany Test Wizualizacji Przestrzennej Purdue (Yoon, 2011), przez kobiety i mężczyzn. Niezależnie od tego, czy instrukcja nawiązywała do stereotypu kobiecości, czy męskości, zapoznający się z nią mężczyźni wypadli istotnie statystycznie lepiej od czytających ją kobiet. Podobnego efektu, zgodnie z oczekiwaniami, nie zaobserwowano w przypadku instrukcji neutralnej. Zgromadzone dane nie pozwoliły natomiast potwierdzić hipotezy głoszącej, iż zdolności metapoznawcze stanowią czynnik regulujący oddziaływanie stereotypów na poziom wykonania zadań poznawczych. Wyniki osób o wysokim poziomie owych zdolności z grup C – F nie różniły się w sposób istotny od rezultatów badanych o niskim ich poziomie.
Wśród ograniczeń badania wymienić należy fakt, że wzięło w nim udział znacznie więcej kobiet (n = 331; 81,5%) niż mężczyzn (n = 75; 18,5%), co podaje w wątpliwość reprezentatywność rezultatów osiągniętych przez tych ostatnich. Ponadto, jako iż związek metapoznania i procesów stereotypizacji stanowi względnie nowe zagadnienie, wskazanym wydaje się zweryfikowanie pozyskanych wyników na drodze dalszych dociekań empirycznych.
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ENG – "Metacognitive skills as a factor regulating the influence of stereotypes on cognitive performance" (full text available in Polish): This thesis deals with the influence of stereotypes on human cognitive performance. Its main goal was to determine whether the level of metacognitive skills can regulate the relationship between the stereotype threat and the stereotype boost effect, and the results obtained in cognitive tasks.
The conducted study procedure consisted of two stages. In the first one, participants completed the Metacognitive Self Scale (Brycz et al., 2019), and the Hagen Matrices Test (Heydasch, 2014). The results obtained in the latter allowed to divide them into six groups, unified in terms of the average level of intellectual abilities. Women were assigned to groups A, C and E, while men were assigned to groups B, D and F. During the second stage of the study, manipulation was used, consisting in presenting the participants with the task they were to face as related to stereotypically masculine (groups C and D) or stereotypically feminine (groups E and F) skills. People assigned to the control groups (A and B) read a gender-neutral instruction.
The analyses performed showed that the activation of gender stereotypes significantly differentiated the results obtained in the cognitive task, which was the Revised Purdue Spatial Visualization Test (Yoon, 2011), by women and men. Regardless of whether the instruction referred to the stereotype of femininity or masculinity, men who familiarized themselves with it performed statistically significantly better than women who read it. A similar effect, as expected, was not observed in the case of the neutral instruction. However, the collected data did not allow to confirm the hypothesis that metacognitive skills are a factor regulating the influence of stereotypes on the level of cognitive tasks performance. The results of people with a high level of these skills from groups C – F did not differ significantly from the results of respondents with a low level of these skills.
The limitations of the study include the fact that significantly more women (n = 331, 81.5%) than men (n = 75, 18.5%) took part in it, which questions the representativeness of the results achieved by the latter. Moreover, as the relationship between metacognition and stereotyping processes is a relatively new issue, it seems advisable to verify the obtained results by means of further empirical research.
→ https://apd.amu.edu.pl/diplomas/155028/
... 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. ...
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.
... Understanding these benefits strengthens one's appreciation of the fitness-enhancing power of sociality in humans. 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. ...
Our economic system is destroying our society and our species ...
We live in a society that accepts an economic system in which lies used to promote sales are legitimized by its courts as just an expression of the “puffery” capitalist enterprises use to get buy behaviors and not chargeable as fraud; products are designed to sell profitably, not benefit their recipients; packaging is designed to hide increases in price, not inform buyers; producers who pollute and destroy our ecosystem declare it is not their concern and we accept it; profits are generated from the sale of offerings that are harmful to humankind yet counted in our measures of economic growth and well-being; our right to redress for harm done to us is legally restricted so as not to discourage future commerce; and producers use the profits they extract from us to coop our political representatives and governance so they may continue their plunder undeterred.
In response to all of this and more, we are told there is no better alternative economic system. Moreover, we are told that we can always choose not to buy. Thus, we have nothing to complain about because every transaction we undertake is, by our acceptance, fair and freely made.
None of this is necessary or valid. All of it is predicated on the false assumptions of a sham economic system that serves the few. Its only legitimacy is as a method of control and exploitation of the many. Worse, the human environment it engenders denies the necessities of life that science has made clear are essential for human survival and humankind’s continuance as a specie.
This book reveals why and how this is happening, why it is not necessary, and offers a valid alternative approach to commerce that elevates human sociality, fosters personal emergence, and nourishes the ecosystem that supports all life.
... 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. ...
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.
... Sociability, or increased social interactions which required navigation of complex social networks, has been proposed as the primary driver behind the increase in brain size in the Pleistocene (Dunbar, 1998). Other scholars argue for other key factorsdespecially diet (Agam and Barkai, 2016). ...
... Thus, even for H. sapiens there are really several Dunbar numbers. Dunbar (2020) develops the point and modifies the "series of values" given in Dunbar (1998). He now gives a benchmark value of 1,500 for tribe size. ...
A long tradition explains technological change as recombination. Within this tradition, this Element develops an innovative combinatorial model of technological change and tests it with 2,000 years of global GDP data and with data from US patents filed between 1835 and 2010. The model explains 1) the pace of technological change for a least the past two millennia, 2) patent citations and 3) the increasing complexity of tools over time. It shows that combining and modifying pre-existing goods to produce new goods generates the observed historical pattern of technological change. A long period of stasis was followed by sudden super-exponential growth in the number of goods. In this model, the sudden explosion of about 250 years ago is a combinatorial explosion that was a long time in coming, but inevitable once the process began at least two thousand years ago. This Element models the Industrial Revolution as a combinatorial explosion.
... Primate brains have evolved in response to selective pressures exerted by the need to operate in complex societies (Dunbar 1998). Such pressures may explain the presence of brain mechanisms specialized to processing social information. ...
Primates have evolved diverse cognitive capabilities to navigate their complex social world. To understand how the brain implements critical social cognitive abilities, we describe functional specialization in the domains of face processing, social interaction understanding, and mental state attribution. Systems for face processing are specialized from the level of single cells to populations of neurons within brain regions to hierarchically organized networks that extract and represent abstract social information. Such functional specialization is not confined to the sensorimotor periphery but appears to be a pervasive theme of primate brain organization all the way to the apex regions of cortical hierarchies. Circuits processing social information are juxtaposed with parallel systems involved in processing nonsocial information, suggesting common computations applied to different domains. The emerging picture of the neural basis of social cognition is a set of distinct but interacting subnetworks involved in component processes such as face perception and social reasoning, traversing large parts of the primate brain.
... 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), amongst other things, variation in brain size was less distinct later on between the Neanderthals and Homo sapiens (see presentation in Galway-Witham et al. 2019; and discussion in Lombard & Högberg 2021). ...
In a previous chapter on the cognition of bow hunting, I argued that it is not unfeasible to explore, nor impossible to cautiously build, multiple strands of evidence that can provide ever-more robust insight into past human minds and their interaction with increasingly extended embodiment through technology. In that contribution it was argued that there exists an inextricable interrelatedness between brain, body, mind, and using (or learning to use) technologies such as the bow and arrow, and that one of the brain regions that may function in a co-evolutionary feedback loop with such technologies may be the precuneus. Here I expand on the link between material engagement and the precuneus, which is said to have developed into its current morphology only in Homo sapiens becoming visible in the fossil record from about 100 000 years ago. I introduce toy bows as instruments of learning bimanual manipulation and visuo-spatial integration throughout childhood, and summarise neuro-cognitive work conducted in the context of modern archery to assess and inform evolutionary interpretations of bow hunting.
... It has been hypothesized that cognitive abilities are constrained by the complexity of the animals' social life (Dunbar 1998;Humphrey 1976). Furthermore, Burkart et al. (2014) suggest that allomaternal care is the best index for proactive prosocial behaviors, which are thought to be one of the factors that foster cooperative behaviors. ...
Cooperative behaviors among individuals of numerous species play a crucial role in social interactions. There is a special interest in investigating the occurrence of cooperation among apes because this knowledge could also shed light on evolutionary processes and help us understand the origin and development of cooperation in humans and primates in general. Gibbons are phylogenetically intermediate between the great apes and monkeys, and therefore represent a unique opportunity for comparisons. The aim of the present study was to discover whether or not white-handed gibbons (Hylobates lar) show cooperative behaviors. In order to test for the respective behaviors, the gibbons were presented with a commonly used experimental cooperative rope-pulling task. The gibbons in this study did not exhibit cooperative behaviors during the problem-solving task. However, prior training procedures could not be fully completed, hence this project constitutes only the onset of exploring cooperative behaviors in gibbons. Additional behavioral observations revealed that the gibbons spent significantly more time "out of arm's reach to everyone", suggesting that they are less often involved in social interactions, than other, more cooperative primates.
... These features make magpies an excellent model species for cognition research. Furthermore, magpies are also highly social birds, which may drive the evolution of more advanced cognition (Humphrey 1976;Dunbar 1998). Some of these social drivers for evolution of complex cognition include the need to maintain and coordinate relationships, keep track of other group members, recognize cooperative partners, and the need to outwit rivals in competitive interactions (Byrne and Whiten 1988;Brosnan et al. 2010;Massen et al. 2014). ...
The string-pulling paradigm is an approach commonly used in the study of animal cognition to investigate problem-solving abilities. This test involves an out-of-reach reward that can only be acquired through pulling a string. Australian magpies (Gymnorhina tibicen tyrannica) can solve cognitive tasks requiring associative and reversal learning, spatial memory, and inhibitory control. Nonetheless, whether magpies can pass a test of means-end understanding—the string-pull test—is unclear. We tested wild magpies on a string-pulling task with five configurations, including a long loose string that required several pulls to obtain food, a short string that only required a single pull to complete, and two short strings—one intact and connected to the food reward; the other broken and unable to yield food when pulled. Of the 11 magpies tested, none solved the long string task at first presentation. Two naïve birds and three, subsequently trained, birds succeeded at the short string. Once proficient at the short string, four of these five birds then solved the long string task; in addition, three learned to choose a functional, intact string over a non-functional, broken string. Overall, these observations provide evidence that Australian magpies have the ability to solve string-pulling tasks but it remains unclear whether they do so by trial-and-error or if they possess means-end understanding.
Significance statement
We found, for the first time, that wild, free-ranging Australian magpies can learn to solve different versions of a string-pulling task; a version with a short string, a long string, and two strings next to each other where one of them was broken and non-functional (broken string task). Some magpies spontaneously solved the task with the short string, where other magpies required training, and magpies only managed to solve the task with the long string after they had succeeded on the short string task. Furthermore, some of the magpies solved the broken string task but required a high number of trials to do so. Overall, our findings show that Australian magpies have the ability to solve string-pulling tasks but it remains unclear whether they do so by trial-and-error or if they understand causal relations between objects.
... Our results indicate cortical correlates of a strong evolutionary interplay 78 between this complexification of visual processing, social cognition 79 and ecology implicating the default mode network 80,81 . The ability of discriminating red hues might 82 be a crucial component in diurnal predator avoidance 83 and potentially foraging as well as for the interpretation of facial features 84 . ...
Studies in comparative neuroanatomy and of the fossil record demonstrate the influence of socio-ecological niches on the morphology of the cerebral cortex, but have led to oftentimes conflicting theories about its evolution. Here, we study the relationship between the shape of the cerebral cortex and the topography of its function. We establish a joint geometric representation of the cerebral cortices of ninety species of extant Euarchontoglires, including commonly used experimental model organisms. We show that variability in surface geometry relates to species’ ecology and behaviour, independent of overall brain size. Notably, ancestral shape reconstruction of the cortical surface and its change during evolution enables us to trace the evolutionary history of localised cortical expansions, modal segregation of brain function, and their association to behaviour and cognition. We find that individual cortical regions follow different sequences of area increase during evolutionary adaptations to dynamic socio-ecological niches. Anatomical correlates of this sequence of events are still observable in extant species, and relate to their current behaviour and ecology. We decompose the deep evolutionary history of the shape of the human cortical surface into spatially and temporally conscribed components with highly interpretable functional associations, highlighting the importance of considering the evolutionary history of cortical regions when studying their anatomy and function.
... One potential factor is selection arising from the social environment of most modern dog breeds, the human family. The social brain hypothesis, the idea that a more complex social environment yields positive selection on social cognitive abilities via increased brain size, is an important hypothesis in the field of brain evolution (Dunbar 1998). While controversial due to variable empirical support (Dunbar and Shultz 2007a;Dunbar and Shultz 2007b;Shultz and Dunbar 2010;van der Bijl and Kolm 2016;DeCasien et al. 2017) especially within Carnivora (Finarelli and Flynn 2009), the social brain hypothesis is intuitively attractive, and the social environment is still considered a potentially important selection pressure on cognitive ability and brain size. ...
Domestication is a well-known example of the relaxation of environmentally-based cognitive selection that leads to reductions in brain size. However, little is known about how brain size evolves after domestication and whether subsequent directional/artificial selection can compensate for domestication effects. The first animal to be domesticated was the dog, and recent directional breeding generated the extensive phenotypic variation among breeds we observe today. Here we use a novel endocranial dataset based on high-resolution CT scans to estimate brain size in 159 dog breeds and analyze how relative brain size varies across breeds in relation to functional selection, longevity, and litter size. In our analyses, we controlled for potential confounding factors such as common descent, gene flow, body size, and skull shape. We found that dogs have consistently smaller relative brain size than wolves supporting the domestication effect, but breeds that are more distantly related to wolves have relatively larger brains than breeds that are more closely related to wolves. Neither functional category, skull shape, longevity, nor litter size was associated with relative brain size, which implies that selection for performing specific tasks, morphology, and life history do not necessarily influence brain size evolution in domesticated species.
... Seeking to explain the large brain size of humans relative to other primates, the "social brain hypothesis" argued that the growing size of human social networks necessitated a change in brain structure and function. 12,13 Although the increased size of social groups, and the concomitant need for brain structures capable of language processing, may not be the only contributor to the growth of the prefrontal cor- tex and the general increase in human brain size, this social process was likely a key contributor. In addition to the size of our networks, humans are nearly unique in the degree to which we have developed social skills that enable us to effectively communicate, empathize, and show altruism. ...
Individuals with more complex jobs experience better cognitive function in old age and a lower risk of dementia, yet complexity has multiple dimensions. Drawing on the Social Networks in Alzheimer Disease study, we examine the association between occupational complexity and cognition in a sample of older adults (N = 355). A standard deviation (SD) increase in complex work with people is associated with a 9% to 12% reduction in the probability of mild cognitive impairment or dementia, a 0.14-0.19 SD increase in episodic memory, and a 0.18-0.25 SD increase in brain reserve, defined as the gap (residual) between global cognitive function and magnetic resonance imaging (MRI) indicators of brain atrophy. In contrast, complexity with data or things is rarely associated with cognitive outcomes. We discuss the clinical and methodological implications of these findings, including the need to complement data-centered activities (e.g., Sudoku puzzles) with person-centered interventions that increase social complexity.
... The primate brain imaging repository can also enable interesting primate comparative neuroimaging with regard to the social brain. Previous comparative MRI studies analyzed the relationship between social network size and the size of brain regions such as the amygdala and prefrontal area in humans ( Bickart et al., 2011 ;Powell et al., 2012 ) to test the social brain hypothesis, an explanation for the unusually large brains of primates, which posits that the size of a social group typical of a species is directly related to the volume of that species' neocortex ( Dunbar, 1998 ). Accessing this imaging repository, users would be able to analyze the relationship between the social network size and the absolute or relative size of brain regions or connection strengths of white matter bundles to directly verify the social brain hypothesis among primates. ...
A comparison of neuroanatomical features of the brain between humans and our evolutionary relatives, nonhuman primates, is key to understanding the human brain system and the neural basis of mental and neurological disorders. Although most comparative MRI studies of human and nonhuman primate brains have been based on brains of primates that had been used as subjects in experiments, it is essential to investigate various species of nonhuman primates in order to elucidate and interpret the diversity of neuroanatomy features among humans and nonhuman primates. To develop a research platform for this purpose, it is necessary to harmonize the scientific contributions of studies with the standards of animal ethics, animal welfare, and the conservation of brain information for long-term continuation of the field. In previous research, we first developed a gated data-repository of anatomical images obtained using 9.4-T ex vivo MRI of postmortem brain samples from 12 nonhuman primate species, and which are stored at the Japan Monkey Centre. In the present study, as a second phase, we released a collection of T2-weighted images and diffusion tensor images obtained in nine species: white-throated capuchin, Bolivian squirrel monkey, stump-tailed macaque, Tibet monkey, Sykes' monkey, Assamese macaque, pig-tailed macaque, crested macaque, and chimpanzee. Our image repository should facilitate scientific discoveries in the field of comparative neuroscience. This repository can also promote animal ethics and animal welfare in experiments with nonhuman primate models by optimizing methods for in vivo and ex vivo MRI scanning of brains and supporting veterinary neuroradiological education. In addition, the repository is expected to contribute to conservation, preserving information about the brains of various primates, including endangered species, in a permanent digital form.
... Second, socio-affective content often engages shared schemas of social interactions (e.g. family dinners in Growth; (Dunbar 1998;Wood et al. 2003;Adolphs et al. 2016) and is often more engaging than its non-social counterpart. Both social and affective information induce shared neural responses during movie-watching (Finn et al. 2018;Chen et al. 2020;Song et al. 2021) and recall (Chen et al. 2017a;Tomita et al. 2021) and may aid in segmentation (Boggia and Ristic 2015;Ristic and Capozzi 2022). ...
Event segmentation is a spontaneous part of perception, important for processing continuous information and organizing it into memory. Although neural and behavioral event segmentation show a degree of inter-subject consistency, meaningful individual variability exists atop these shared patterns. Here we characterized individual differences in the location of neural event boundaries across four short movies that evoked variable interpretations. Event boundary alignment across subjects followed a posterior-to-anterior gradient that was tightly correlated with the rate of segmentation: slower-segmenting regions that integrate information over longer time periods showed more individual variability in boundary locations. This relationship held irrespective of the stimulus, but the degree to which boundaries in particular regions were shared versus idiosyncratic depended on certain aspects of movie content. Furthermore, this variability was behaviorally significant in that similarity of neural boundary locations during movie-watching predicted similarity in how the movie was ultimately remembered and appraised. In particular, we identified a subset of regions in which neural boundary locations are both aligned with behavioral boundaries during encoding and predictive of stimulus interpretation, suggesting that event segmentation may be a mechanism by which narratives generate variable memories and appraisals of stimuli.
... Consistently with Dunbar's previous work (Dunbar, 1998a(Dunbar, , 1998b, the main lens used to explain the evolution of religious ritual in the target book is through social bonding. Religious ritual is posited as a social mechanism-alongside laughter, singing, dancing, and storytelling-that facilitates interpersonal bonding (p. ...
Robin Dunbar’s book How Religion Evolved brings back the ethos of “big theories” that was characteristic of scholars of religion in the late 19th and early 20th centuries. Although the previous approaches were rightfully criticized for unilinear views of cultural evolution, the aftermath of these critiques condemned (perhaps a bit prematurely) big theories to oblivion (Kundt, 2015). With novel tools for understanding biological and cultural evolution at our hands, it may be a good time to carefully reinvigorate “big theorizing” in a more informed way and ask, as Dunbar does, how religion evolved. The target book represents a valuable step in this direction and provides a general model suggesting that religions first evolved as animistic traditions emerging from individual mystical experiences and later merged into cultural systems facilitating social bonding and creating communities.
While I agree that religions (or, more specifically, religious systems) evolved, and we may expect the evolution to be cumulative (building on previous adaptations), I have an alternative view of the timing and sequence of these evolutionary events. Specifically, I will focus my commentary on Dunbar’s proposition about the function of religious ritual and the timing of its evolution. Since ritual behavior is an essential component of any functioning religious system (Sosis, 2016, 2019), the way we model the evolution of ritual will determine our general understanding of the evolution of religion.
... The group size and complex dynamics of ancestral wolftype populations may also have provided an important substrate for the evolution of the human-dog relationship. Typically, social species display complex social signals (Dobson 2009b(Dobson , 2009a, which, according to the "Social brain hypothesis", also requires advanced cognition to navigate these more demanding social environments (Dunbar 1998;Whiten and Byrne 1988). This, coupled with the need to operate within a framework of rapid exchanges to prevent harm to either or both parties (Mills and Westgarth 2017), would favour the development of these abilities within both visual and acoustic sensory channels. ...
Comparative studies of human–dog cognition have grown exponentially since the 2000’s, but the focus on how dogs look at us (as well as other dogs) as social partners is a more recent phenomenon despite its importance to human–dog interactions. Here, we briefly summarise the current state of research in visual perception of emotion cues in dogs and why this area is important; we then critically review its most commonly used methods, by discussing conceptual and methodological challenges and associated limitations in depth; finally, we suggest some possible solutions and recommend best practice for future research. Typically, most studies in this field have concentrated on facial emotional cues, with full body information rarely considered. There are many challenges in the way studies are conceptually designed (e.g., use of non-naturalistic stimuli) and the way researchers incorporate biases (e.g., anthropomorphism) into experimental designs, which may lead to problematic conclusions. However, technological and scientific advances offer the opportunity to gather much more valid, objective, and systematic data in this rapidly expanding field of study. Solving conceptual and methodological challenges in the field of emotion perception research in dogs will not only be beneficial in improving research in dog–human interactions, but also within the comparative psychology area, in which dogs are an important model species to study evolutionary processes.
... Humans are an innately social species, evolved to rely on interacting and bonding with other people for childcare (10), resources (11), and buffering against stress (12). The complex human societies most of us find ourselves in today are not immune from this need for deep social bonds: From sprawling cities comprising millions of individuals, people tend to seek out social circles of a handful of individuals whom they come to rely on (13)(14)(15). ...
At times of turmoil, such as during disasters, social crises, or pandemics, our social bonds can be key to receiving support and gaining certainty about the right course of action. In an analysis combining two global datasets (N = 13,264) collected during the first wave of the COVID-19 pandemic, this study examined how social bonds with close social circles (i.e., family and friends) and extended groups (i.e., country, government, and humanity) relate to engagement in health behaviors and psychological well-being. Results revealed that only family bonding was associated with self-reported engagement in health behaviors. Being strongly bonded with both close circles and extended groups predicted less anxiety and depression and better well-being, particularly for those who were bonded with more groups. These findings highlight that close and extended social bonds offer different sources of support and direction during the most challenging of circumstances and that continuous investment is needed to forge and maintain both.
... Culture is a system of expectations and perspectives shared by a social group that is shaped and passed between members through implicit (e.g., nonverbal approval or disapproval) and explicit means (Boyd & Richeson, 2005;Shweder & Sullivan, 1993). Human groups naturally form their own cultures partly to promote order among members (Boyd & Richerson, 2005;Dunbar, 1998;Geertz, 1973), but also to create a social identity that binds the group together and differentiates them from other groups, providing a sense of belonging that is critical to well-being (Baumeister & Leary, 1995;Deci & Ryan, 2012;Tajfel & Turner, 1979). Any person whose sense of self and related experiences are influenced by the norms, values, and beliefs (i.e., culture) of multiple meaningful social groups could be considered Multicultural (Nguyen & Benet-Martínez, 2007). ...
Most research has investigated Multiracial and Multicultural populations as separate topics, despite demographic and experiential overlap between these. This Element bridges that divide by reviewing and comparing Multiracial and Multicultural research to date-their origins, theoretical and methodological development, and key findings in identity negotiation, socialization, and discrimination-to identify points of synthesis and differentiation to guide future research. It highlights challenges researchers face when studying these populations because such research topics necessitate that one moves beyond previous frameworks and theories to grapple with identity as flexible, malleable, and influenced both by internal factors and external perceptions. The areas of overlap and difference are meaningful and illustrate the social constructive nature of race and culture, which is always in flux and being re-defined.
... It has been proposed that the size of the brain is correlated with the size of the group of animals that live together (Marino et al., 2000), due to a potential relationship between the size of the neocortex and cognitive abilities such as intraspecific recognition (Dunbar, 1998). Marino et al. (2007) observed that the expansion of different zones of the neocortex in cetaceans is linked to high cognitive functions like attention, social consciousness, judgment and intuition. ...
Ornithopod dinosaurs were a successful group before they became extinct at the end of the Cretaceous. They were present on every continent, though they were rare in the Southern Hemisphere. We present the results of our work on the brain of these dinosaurs as an attempt to determine which evolutionary trends affected it. Old and new technologies allow us to peer into the skull of long extinct animals and retrieve information about their brain. First we provide a short description of the brain of ornithopod dinosaurs from Europe and Asia, then we sum up the characteristics that can be gathered from it. The presence of valleculae helps us to assess the actual size of the brain with more confidence. The olfactory peduncles are large and these animals had a good sense of smell. There is a trend toward an increase in the size of the cerebral hemispheres, and a more straight-lined brain. The latter can be the result of the ontogeny and the size achieved by the adult animal on the development of the brain. Other characteristics, like the development of the cerebral hemispheres and the encephalization quotient, allude to Hadrosauridae having had cognitive abilities more developed than previously assumed. This is in adequacy with other data from the physical characteristics (e.g., crests) and the social life (e.g., living in herds, communal nests) of these dinosaurs, which denote high and complex behaviors like care for their young, sexual courtship, and gregariousness.
... Provisioning would have been prevalent among adults, and the 571 division of labor was promoted under the risky environments of large terrestrial 572 predators. The complexities of diet and social life followed the increase in brain 573 size (Jerison 1973;Clutton-Brock and Harvey 1980;Milton 1981;Dunbar 1996). 574 Ripe fruits, extractive foods, tool use, and increasing group size with complex social 575 interactions improved the memories and intellectual behavior of H. erectus, H. 576 neanderthalensis, and H. sapiens. ...
Spider monkeys are one of the most widespread New World primate genera, ranging from southern Mexico to Bolivia. Although they are common in zoos, spider monkeys are traditionally very difficult to study in the wild, because they are fast moving, live high in the canopy and are almost always found in small subgroups that vary in size and composition throughout the day. This book is an assimilation of both published and previously unpublished research. It is a comprehensive source of information for academic researchers and graduate students interested in primatology, evolutionary anthropology and behavioral ecology and covers topics such as taxonomy, diet, sexuality and reproduction, and conservation.
... Moreover, the overall ecological complexity that a species is confronted to may also include its social environment. First proposed to explain the brain evolution in primates, the Social Brain Hypothesis (SBH) posits that cognitive requirements of social interactions are the main driver of encephalization change at the macroevolutionary scale 32 . How to characterize and accurately measure sociality is still a matter of debate [33][34][35][36] . ...
The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans' evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments.
... There are several non-mutually exclusive hypotheses that attempt to explain the evolution of brain size variation within mammals. Some of these relate to selection pressures that might be imposed on the individual (Milton 1981;DeCasien et al. 2017;Rosati 2017) or social level (Dunbar 1998). Others emphasise the metabolic and developmental Orlin S. Todorov tdrvorlin@gmail.com 1 may then be masked by more pronounced ones, or effects on smaller clades may disappear when analysed in the context of all mammals. ...
Studies on the evolution of brain size variation usually focus on large clades encompassing broad phylogenetic groups. This risks introducing ‘noise’ in the results, often obscuring effects that might be detected in less inclusive clades. Here, we focus on a sample of endocranial volumes (endocasts) of 18 species of rabbits and hares (Lagomorpha: Leporidae), which are a discrete radiation of mammals with a suitably large range of body sizes. Using 60 individuals, we test five popular hypotheses on brain size and olfactory bulb evolution in mammals. We also address the pervasive issue of missing data, using multiple phylogenetic imputations as to conserve the full sample size for all analyses. Our analyses show that home range and burrowing behaviour are the only predictors of leporid brain size variation. Litter size, which is one of the most widely reported constraints on brain size, was unexpectedly not associated with brain size. However, a constraining effect may be masked by a strong association of litter size with temperature seasonality, warranting further study. Lastly, we show that unreasonable estimations of phylogenetic signal (Pagel’s lamba) warrant additional caution when using small sample sizes, such as ours, in comparative studies.
... - Riley and Bezanson (2018, p. 506) Compared to captive cognition research, studying the cognitive abilities of wild primates has historically been the product of systematic behavioral observation research (Tomasello & Call, 2011). For instance, observing the behavior of large primate social groups has been critical to understanding the intricacies of the cognitive mechanisms required to manage social complexity (Dunbar, 1998). Such observational studies are largely free from the types of welfare-based burdens and considerations described above. ...
Researchers have studied non-human primate cognition along different paths, including social cognition, planning and causal knowledge, spatial cognition and memory, and gestural communication, as well as comparative studies with humans. This volume describes how primate cognition is studied in labs, zoos, sanctuaries, and in the field, bringing together researchers examining similar issues in all of these settings and showing how each benefits from the others. Readers will discover how lab-based concepts play out in the real world of free primates. This book tackles pressing issues such as replicability, research ethics, and open science. With contributors from a broad range of comparative, cognitive, neuroscience, developmental, ecological, and ethological perspectives, the volume provides a state-of-the-art review pointing to new avenues for integrative research.
... brain size and eye size) vary across taxa (Walls, 1942;Land & Fernald, 1992;Aiello & Wheeler, 1995;Striedter, 2005). The drivers of the observed variation in brain size have been the focus of much research (Bauchot et al., 1977;Allman et al., 1993;Aiello & Wheeler, 1995;Dunbar, 1998;Striedter, 2005;Sol et al., 2005Sol et al., , 2008González-Lagos et al., 2010;Amiel et al., 2011;Hoops et al., 2017;Axelrod et al., 2021). Explanations for variation in brain size include life-history strategy (Allman et al., 1993;Deaner et al., 2003;Yu et al., 2018), shifts in cognition (Jacobs et al., 1990;Sol et al., 2005;MacLean et al., 2014) and ecological conditions (Huber et al., 1997;Safi & Dechmann, 2005). ...
Links between contrasting ecological conditions and evolutionary shifts in neurosensory components, such as brain and eye size, are accumulating. Whether selection operates in a different manner on these traits between sexes is unclear. Trinidadian killifish (Anablepsoides hartii) are found in sites with and without predators. Male killifish from sites without predators have evolved larger brains and eyes than males from sites with predators. These differences in brain size are present early in life but disappear in adult size classes. Here, we evaluated female brain growth allometries to determine whether females exhibit similar size-specific differences in brain size between sites that differ in predation intensity. We also quantified brain size and structure and eye size to determine whether these structures co-evolved in a sex-specific manner. We found that female brain growth allometries did not differ across populations. Yet, female killifish from sites without predators exhibited a larger cerebellum, optic tectum and dorsal medulla early in life (before maturation), although such differences disappeared in larger size classes. Females from sites with predators exhibited similar patterns in brain growth to males in those sites; therefore, shifts in brain size and structure are driven by differences between sexes in sites without predators. We also found evidence for covariation between brain and eye size in both sexes despite different levels of variation in both structures, suggesting that these structures might covary to fluctuating degrees in sex-specific ways. We conclude that differential investment in brain tissue in sites without predators might be linked to varying reproductive and cognitive demands between the sexes.
... Although some differences between wild and captive animals have been reported in their levels of performance with certain cognitive tasks (Benson-Amram et al., 2013;Cauchoix et al., 2017), it is commonly agreed that cognitive abilities have evolved throughout a species' evolutionary history. In the case of primates, for example, their physical cognitive skills are thought to have evolved in response to the demands of their dietary specializations (Tomasello and Herrmann, 2010), while their social cognitive skills have been suggested to have evolved in response to the complexity of their social systems (Dunbar, 1998). Although we cannot exclude the possibility that the results of our study may have been affected by the captive setting and thus cannot be generalized to the species level, we are nevertheless confident that our findings may contribute to a better understanding of the mechanisms underlying cognitive abilities and the selective pressure(s) which may have promoted their evolution. ...
We assessed two aspects of numerical cognition in a group of nine captive spider monkeys (Ateles geoffroyi). Petri dishes with varying amounts of food were used to assess relative quantity discrimination, and boxes fitted with dotted cards were used to assess discrete number discrimination with equally-sized dots and various-sized dots, respectively. We found that all animals succeeded in all three tasks and, as a group, reached the learning criterion of 70% correct responses within 110 trials in the quantity discrimination task, 160 trials in the numerosity task with equally-sized dots, and 30 trials in the numerosity task with various-sized dots. In all three tasks, the animals displayed a significant correlation between performance in terms of success rate and task difficulty in terms of numerical similarity of the stimuli and thus a ratio effect. The spider monkeys performed clearly better compared to strepsirrhine, catarrhine, and other platyrrhine primates tested previously on both types of numerical cognition tasks and at the same level as chimpanzees, bonobos, and orangutans. Our results support the notion that ecological traits such as a high degree of frugivory and/or social traits such as a high degree of fission-fusion dynamics may underlie between-species differences in cognitive abilities.
... Structural differences are also associated with social functioning. In this respect, the so-called social brain hypothesis proposes that the primate neocortex (particularly the temporal lobe) has progressively increased in size over evolution, in order to support the increasingly demanding computations necessary to deal with larger and more complex social groups (Dunbar, 1998). This also applies to the amygdala, which in monkeys shows larger volume as social group size increases, in both the basolateral and the superficial nuclei (Aggleton, 2000). ...
The amygdala is a core structure in the anterior medial temporal lobe, with an important role in several brain functions involving memory, emotion, perception, social cognition, and even awareness. As a key brain structure for saliency detection, it triggers and controls widespread modulatory signals onto multiple areas of the brain, with a great impact on numerous aspects of adaptive behavior. Here we discuss the neural mechanisms underlying these functions, as established by animal and human research, including insights provided in both healthy and pathological conditions.
... Cognitive sexual dimorphism observed in spatial learning and problem-solving that is linked to sexual selection processes (Lucon-Xiccato and Bisazza, 2016), is also likely to manifest across alternative male phenotypes that vary in territorial use or innovation to gain access to females. Early neurobiological research suggests males with alternative strategies might be employing different cognitive strategies resulting in differential investment in neocortex size (Dunbar, 1998;Pawlowski and Dunbar, 1999); and neurogenomic work suggests females experiencing multiple male phenotypes engage more genomic synaptic plasticity pathways in the brain than females interacting with a single (coercive) tactic (Lynch et al., 2012;Wang et al., 2014;Cummings and Ramsey, 2015). Lastly, the correlations between behavioral tendencies and cognitive performances [cognitive-behavioral syndromes; Carere and Locurto (2011)] that are beginning to be characterized between the sexes (Titulaer et al., 2012;Etheredge et al., 2018;Wallace et al., 2020) are predicted to diverge across alternative male phenotypes (Carazo et al., 2014). ...
Sexual selection is a powerful diversifier of phenotype, behavior and cognition. Here we compare cognitive-behavioral traits across four reproductive phenotypes (females and three alternative males) of wild-caught ocellated wrasse (Symphodus ocellatus). Both sex and alternative male phenotypes are environmentally determined with sex determination occuring within the first year, and males transition between alternative phenotypes across 2 years (sneaker to satellite or satellite to nesting). We captured 151 ocellated wrasse and tested them on different behavior and cognition assays (scototaxis, shoaling, and two detour-reaching tasks). We found greater divergence across alternative male reproductive phenotypes than differences between the sexes in behavior, problem-solving, and relationships between these traits. Nesting males were significantly less bold than others, while sneaker males were faster problem-solvers and the only phenotype to display a cognitive-behavioral syndrome (significant correlation between boldness and problem-solving speed). Combining these results with prior measurements of sex steroid and stress hormone across males, suggests that nesting and sneaker males represent different coping styles. Our data suggests that transitioning between alternative male phenotypes requires more than changes in physiology (size and ornamentation) and mating tactic (sneaking vs. cooperation), but also involves significant shifts in cognitive-behavioral and coping style plasticity.
... 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. ...
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.
... 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. ...
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 chapter highlights a simple but important principle for understanding the
evolution of cooperation in our species. This principle is that below a certain
population level, societies can make collective decisions without formal institutions
of power. Once a certain threshold is reached, however, more formal
institutions are required in order to signal trust, the basis of sustained cooperation
as articulated by Elinor Ostrom and others in the last few decades.
The human brain supports social cognitive functions, including Theory of Mind, empathy, and compassion, through its intrinsic hierarchical organization. However, it remains unclear how the learning and refinement of social skills shapes brain function and structure. We studied if different types of social mental training induce changes in cortical function and microstructure, investigating 332 healthy adults (197 women, 20-55 years) with repeated multimodal neuroimaging and behavioral testing. Our neuroimaging approach examined longitudinal changes in cortical functional gradients and myelin-sensitive T1 relaxometry, two complementary measures of cortical hierarchical organization. We observed marked changes in intrinsic cortical function and microstructure, which varied as a function of social training content. In particular, cortical function and microstructure changed as a result of attention-mindfulness and socio-cognitive training in regions functionally associated with attention and interoception, including insular and parietal cortices. Conversely, socio-affective and socio-cognitive training resulted in differential microstructural changes in regions classically implicated in interoceptive and emotional processing, including insular and orbitofrontal areas, but did not result in functional reorganization. Notably, longitudinal changes in cortical function and microstructure predicted behavioral change in attention, compassion and perspective-taking. Our work demonstrates functional and microstructural plasticity after the training of social-interoceptive functions, and illustrates the bidirectional relationship between brain organisation and human social skills.
In contrast to long-term 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 transient alters does not display such a systematic decay, instead showing a lack of any dominant trends. This means that the communication volume of egos to groups of similar transient alters is stable. We show that alters with longer lifetimes in ego’s network receive more calls, with the lifetime of the relationship being predictable from call volume within the first few weeks of first contact. This is observed across all three countries, which include samples of egos at different life stages. The relation between early call volume and lifetime is consistent with the suggestion that individuals initially engage with a new alter so as to evaluate their potential as a tie in terms of homophily.
As the 2020 United State Presidential election presented tense partisan conflicts, we sought to explore whether and how such a social and ideological fissure can lead to large-scale politically motivated avoidance behaviours. Building on prior literature, we examine how social media behaviours (i.e. expressive social media news use and political discussion with weak ties) and social psychological attitudes (i.e. surveillance anxiety) are associated with selective avoidance on social media. Further, we explore cognitive ability's direct and indirect roles in influencing avoidance behaviours. We used online panel survey data collected during the 2020 election to test our assumptions. The findings suggest that those with high levels of expressive social media news use, political discussions with weak ties, and surveillance anxiety engage in more frequent selective avoidance. On the contrary, those with high cognitive ability are less likely to engage in selective avoidance. Furthermore, moderation effects suggest that low cognitive users with greater surveillance anxiety and frequent discussions with weak ties are most accustomed to selective avoidance. Finally, we discuss the theoretical and policy implications of these findings.
De seneste 20 års forskning i stress har peget på en lang række problemer i forbindelse med den klassiske stressteori, udformet af Cannon og Selye. I artiklen argumenteres for, at et lovende bud på et svar på disse udfordringer kan bestå i udformningen af en stressteori, der også inddrager andre og parallelt udviklede psykofysiologiske systemer. Dette indebærer (i) en sondring mellem det evolutionært ældre GAS (Selye) og (ii) det nyere system, der er baseret på HPA (Cannon), og (iii) at stresssystemets regulering anskues ud fra den nyere allostatiske model (Sterling, McEwen), som derved erstatter den oprindelige homeostase-model. Denne fornyede forståelse bør også omfatte (iv) den poly-vagale teori. Teorien åbner for inddragelsen af stress som kommunikation og social regulering. Dette åbner for en bedre forståelse af, hvordan stress påvirker sociale relationer og interaktioner. Sidst, men ikke mindst (v), argumenteres for inddragelse af teorier om social smerte. Denne synsvinkel peger på, at stress medfører, regulerer og skærper oplevelse af social smerte ved trussel. Et sådant moderniseret og flerstrenget system vil kunne åbne nye perspektiver, både i forhold til diagnostik og behandling af stress og afledte syndromer.
Recent machine learning approaches have been effective in Artificial Intelligence (AI) applications. They produce robust results with a high level of accuracy. However, most of these techniques do not provide human-understandable explanations for supporting their results and decisions. They usually act as black boxes, and it is not easy to understand how decisions have been made. Explainable Artificial Intelligence (XAI), which has received much interest recently, tries to provide human-understandable explanations for decision-making and trained AI models. For instance, in digital agriculture, related domains often present peculiar or input features with no link to background knowledge. The application of the data mining process on agricultural data leads to results (knowledge), which are difficult to explain. In this paper, we propose a knowledge map model and an ontology design as an XAI framework (OAK4XAI) to deal with this issue. The framework does not only consider the data analysis part of the process, but it takes into account the semantics aspect of the domain knowledge via an ontology and a knowledge map model, provided as modules of the framework. Many ongoing XAI studies aim to provide accurate and verbalizable accounts for how given feature values contribute to model decisions. The proposed approach, however, focuses on providing consistent information and definitions of concepts, algorithms, and values involved in the data mining models. We built an Agriculture Computing Ontology (AgriComO) to explain the knowledge mined in agriculture. AgriComO has a well-designed structure and includes a wide range of concepts and transformations suitable for agriculture and computing domains.
Considering that the performance of personality predictors are not consistently increasing throughout the years, as an alternative, the idea was to provide big5 personality traits lexicon based on the Essay dataset. The weight of relevance for every trait of each word is calculated by tf/idf on the words in the Essay dataset. However, it was eventually realized that three personalities wordset were overlapped requiring a change of course. The research changed the underlying model from big5 to Vann Joines’ mental processes as it appear to suit better with the empirical findings. The resulting lexicon dataset is composed with 3432 commonly used words and 3639 avoided prone words for each mental process. The commonly used words are capable of covering 81% of the Twitter Personality dataset.
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.
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.
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.
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.
The mental map of wild chimpanzees is analyzed in the context of their transports of clubs and stones used for cracking two
species of nuts of different hardness,Coula edulis andPanda oleosa, in the Tai National Park (Ivory Coast). For the harderPanda nuts, they transport the harder hammers, i.e., almost exclusively stones, hammers of greater weight, and the transports are
longer than forCoula nuts. The analysis made for the transports forPanda nuts shows that they seem to remember the location of stones and to choose the stones so as to keep the transport distance
minimal. The chimpanzees seem to possess an Euclidian space, which allows them to somehow measure and remember distances;
to compare several such distances so as to choose the stone with the shortest distance to a goal tree; to correctly locate
a new stone location with reference to different trees; and to change their reference point so as to measure the distance
to eachPanda tree from any stone location. They also combine the weight and the distance. The wild chimpanzees of the Tai National Park
seem to possess concrete operation abilities in spatial representation.
The visual perspective-taking ability of 4 chimpanzees (Pan troglodytes) was investigated. The subjects chose between information about the location of hidden food provided by 2 experimenters who randomly alternated between two roles (the guesser and the knower). The knower baited 1 of 4 obscured cups so that the subjects could watch the process but could not see which of the cups contained the reward. The guesser waited outside the room until the food was hidden. Finally, the knower pointed to the correct cup while the guesser pointed to an incorrect one. The chimpanzees quickly learned to respond to the knower. They also showed transfer to a novel variation of the task, in which the guesser remained inside the room and covered his head while the knower stood next to him and watched a third experimenter bait the cups. The results are consistent with the hypothesis that chimpanzees are capable of modeling the visual perspectives of others.
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.
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.
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.
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.
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.
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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.
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.
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).
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.
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)
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.
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.
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.
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.
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.
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.
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.