Richard W Byrne

University of St Andrews · School of Psychology and Neuroscience

Opinion piece: ape gestures are made intentionally, inviting parallels with human language; but how similar are their gestures to words? Here we ask this in three ways, considering: flexibility and ambiguity, first- and second-order intentionality, and usage in interactive exchanges. Many gestures are used to achieve several, often very distinct, g...

There is great diversity in social behavior across the animal kingdom. Understanding the factors responsible for this diversity can help inform theory about how sociality evolves and is maintained. The Australian Tree Skink (Egernia striolata) exhibits inter- and intra-population variability in sociality and is therefore a good system for informing...

The ability to produce viable offspring without recently mating, either through sperm storage or parthenogenesis, can provide fitness advantages under a suite of challenging ecological scenarios. Using genetic analysis, we demonstrate that three wild-caught female Tree Skinks (Egernia striolata) reproduced in captivity with no access to males for o...

Within comparative psychology, the evolution of animal cognition is typically studied either by comparing indirect measures of cognitive abilities (e.g., relative brain size) across many species or by conducting batteries of decision-making experiments among (typically) a few captive species. Here, we propose a third, complementary approach: inferr...

In most languages, individual words can be ambiguous between several different meanings, but through syntax and context the intended meaning of an ambiguous word usually becomes apparent. Many great ape gestures also have ambiguous meanings, which poses the problem of how individuals can interpret the signaller’s intended meaning in specific instan...

Keywords: age difference altricialeprecocial cognition ID/ED attentional set shifting squamates In altricial species, young rely on parental care and brain maturation mainly occurs after birth. In pre-cocial species, young are born at a more advanced developmental stage in need of less or no parental care and brain development is mostly completed a...

Video Clip (32 seconds) http://dx.doi.org/10.1037/ebs0000175.supp Female Eastern chimpanzee (Pan troglodyte schweinfurthii) in the wild: Monika (16 yrs) and her infant (1 week) of Waibira community in the Budongo Forest Reserve, Uganda. Credit to Hella Peter for the clip.

Intrinsic to an evolved disease avoidance account of disgust is Darwin's assumption of continuity between the emotional lives of humans and animals. However, beyond the case of avoiding stimuli that taste bad, there has been little exploration of the existence of basic disgust elicitors in animals. Moreover, one influential perspective holds that d...

Behavioural flexibility, the ability to adjust behaviour to environmental change by adapting existing skills to novel situations, is key to coping with, for example, complex social interactions, seasonal changes in food availability or detecting predators. We tested the tree skink, Egernia striolata, a family-living skink from eastern Australia, in...

Many studies have been carried out into both motor and sensory laterality of horses in agonistic and stressful situations. Here we examine sensory laterality in affiliative interactions within four groups of domestic horses and ponies (N = 31), living in stable social groups, housed at a single complex close to Vienna, Austria, and demonstrate for...

An animal’s social environment can be both dynamic and complex. Thus, social species often garner fitness benefits through being plastic in their social behavior. Yet, social plasticity can be constrained by an individual’s experience. We examined the influence of early social environment on social behavior in the tree skink (Egernia striolata), a...

Social learning is widespread among family living species, particularly mammals and birds with relatively high levels of social complexity and overt social interaction. However, the occurrence of social learning has never been documented in lizards with kin-based sociality, which have less obvious social interactions. We tested for social learning...

Cross-species comparison of great ape gesturing has so far been limited to the physical form of gestures in the repertoire, without questioning whether gestures share the same meanings. Researchers have recently catalogued the meanings of chimpanzee gestures, but little is known about the gesture meanings of our other closest living relative, the b...

R code for randomisation procedure. (R)

Values for Fig 1. By gesture type, the ASOs achieved and the number and proportion of instances that each ASO is achieved, ordered by the proportion for which the primary ASO is achieved (largest to smallest). (DOCX)

Individuals contributing data for ASO analysis. Number of individuals in each age and sex category that contributed data to analysis of ASOs for wild bonobos. (DOCX)

Raw data and matrices for bonobo and chimpanzee gesture meanings. (XLSX)

The social environment during development can affect learning; for example, raising an obligate social mammal in isolation can hinder their learning ability. However, we know little about how the social environment impacts learning in less-studied, facultatively social taxa, like family-living lizards. We reared tree skinks (Egernia striolata) in t...

Current systems of categorising ape gestures are typically subjective, relying on human intuition. We have systematised the features on which categorization depends (movement; body part; one/both limbs; use of detached object; rhythmic repetition; contact with recipient), showing that a potential repertoire of over 1000 gestures is physically possi...

Behavioural flexibility in the Tree Skink (Egernia striolata) tested through set-shifting

Early social environment can play a significant role in shaping behavioural development. For instance, in many social mammals and birds, isolation rearing results in individuals that are less exploratory, shyer, less social and more aggressive than individuals raised in groups. Moreover, dynamic aspects of social environments, such as the nature of...

In animal communication, signallers and recipients are typically different: each signal is given by one subset of individuals (members of the same age, sex, or social rank) and directed towards another. However, there is scope for signaller–recipient interchangeability in systems where most signals are potentially relevant to all age–sex groups, su...

Tactical deception has been widely reported in primates on a functional basis, but details of behavioral mechanisms are usually unspecified. We tested a pair of chimpanzees ( Pan troglodytes ) in the informed forager paradigm, in which the subordinate saw the location of hidden food and the dominant did not. We employed cross‐correlations to examin...

The discovery of new evidence in the archaeological record naturally invites interpretation and deeper intellectual probing. What novel attributes of brains, minds or behavioural and cultural lives were necessary for such finds to have come into existence: Symbolic thought? Planning? Language? Enhanced memory? The very fragmentary nature of materia...

Résumé Le pointage référentiel est important dans le développement de la compréhension du langage chez l’enfant, et est souvent considéré comme une capacité unique de l’homme. Bien que les grands singes utilisent le pointage en captivité, en général à destination d’un public humain, cela a été interprété comme un mode d’interaction appris des soign...

The discovery of new evidence in the archaeological record naturally invites interpretation and deeper intellectual probing. What novel attributes of brains, minds or behavioural and cultural lives were necessary for such finds to have come into existence: Symbolic thought? Planning? Language? Enhanced memory? The very fragmentary nature of materia...

Research on great ape gestural communication has hitherto prioritised the signaller, focusing on the expressed repertoire, the set of gesture types that an individual deploys. In this study of wild bonobos (Pan paniscus), we also examine the understood repertoire, the set of gesture types that a recipient understands: a recipient understands a gest...

We aimed to investigate developmental continuities between a range of early social and communicative abilities (including gestural communication) and language acquisition in children aged between 11 and 41 months. Initiation of joint attention and imitation were strongly correlated to language comprehension and production. Moreover, the analysis of...

Language's intentional nature has been highlighted as a crucial feature distinguishing it from other communication systems. Specifically, language is often thought to depend on highly structured intentional action and mutual mindreading by a communicator and recipient. Whilst similar abilities in animals can shed light on the evolution of intention...

Comparative analysis of the gestural communication of our nearest animal relatives, the great apes, implies that humans should have the biological potential to produce and understand 60–70 gestures, by virtue of shared common descent. These gestures are used intentionally in apes to convey separate requests, rather than as referential items in synt...

OBJECTIVE The purpose of this study was to assess the positive predictive value of postresection outcomes obtained by presurgical subtracted ictal SPECT in patients with lesional (MRI positive) and nonlesional (MRI negative) refractory extratemporal lobe epilepsy (ETLE) and temporal lobe epilepsy (TLE). Specifically, outcomes were compared between...

Research on great ape gestural communication has hitherto prioritised the signaller, focusing on the expressed repertoire, the set of gesture types that an individual deploys. In this study of wild bonobos ( Pan paniscus ), we also examine the understood repertoire, the set of gesture types that a recipient understands: a recipient understands a ge...

Female chimpanzees, Pan troglodytes, are usually depicted as sexually submissive and bound by male coercion, because males are able to monopolize oestrous females, limiting a female's options for mate choice. We present behavioural data from a group of wild chimpanzees during a rare period in which up to 10 females cycled simultaneously, which prev...

Ecological complexity has been proposed to play a crucial role in primate brain-size evolution. However, detailed quantification of ecological complexity is still limited. Here we assess the spatio- temporal distribution of tropical fruits and young leaves, two primary chimpanzee (Pan troglodytes) foods, focusing on the predictability of their avai...

Brain size has traditionally been employed as a measurable proxy for species intelligence. Using allometric scaling of brain size relative to body size shows the biological cost suffered from investment in brain tissue. Shifts in diet type are the engine permitting increased investment in brain tissue because higher energy diets allow a larger brai...

Understanding animal episodic-like memory is important for tracing the evolution of the human mind. However, our knowledge about the existence and nature of episodic-like memory in non-human primates is minimal. We observed the behaviour of a wild male chacma baboon faced with a trade-off between protecting his stationary group from aggressive extr...

We are in a new epoch, the Anthropocene, and research into our closest living relatives, the great apes, must keep pace with the rate that our species is driving change. While a goal of many studies is to understand how great apes behave in natural contexts, the impact of human activities must increasingly be taken into account. This is both a chal...

We are in a new epoch, the Anthropocene, and research into our closest living relatives, the great apes, must keep pace with the rate that our species is driving change. While a goal of many studies is to understand how great apes behave in natural contexts, the impact of human activities must increasingly be taken into account. This is both a chal...

Fun is functional: play is evolution's way of making sure animals acquire and perfect valuable skills in circumstances of relative safety. Yet precisely what animals find fun has seldom been examined for what it can potentially reveal about how they represent and think about the world. Copyright © 2015 Elsevier Ltd. All rights reserved.

Understanding animal episodic-like memory is important for tracing the evolution of the human mind. However, our knowledge about the existence and nature of episodic-like memory in nonhuman primates is minimal. We observed the behaviour of a wild male chacma baboon faced with a trade-off between protecting his stationary group from aggressive extra...

The gestural communication of great apes is a rich and complex system. It is used in a flexible manner with the intention to communicate specific goals to specific individuals - as such, it shares many of the basic attributes of human language, supporting the idea that the two systems share a common evolutionary root. Significant advances in the su...

In a dyadic informed forager task, chimpanzees (Pan troglodytes) are known to exploit the knowledge of informed subordinates; however, the behavioral mechanisms they employ are unknown. It is tempting to interpret outcome measures, such as which individual obtained the food, in a cognitively richer way than the outcomes may justify. We employed a d...

Evidence of social learning, whereby the actions of an animal facilitate the acquisition of new information by another, is taxonomically biased towards mammals, especially primates, and birds. However, social learning need not be limited to group-living animals because species with less interaction can still benefit from learning about potential pr...

How do animals determine when others are able and disposed to receive their communicative signals? In particular, it is futile to make a silent gesture when the intended audience cannot see it. Some non-human primates use the head and body orientation of their audience to infer visual attentiveness when signalling, but whether species relying less...

Chimpanzees' use of gesture was described in the first detailed field study [1, 2], and natural use of specific gestures has been analyzed [3-5]. However, it was systematic work with captive groups that revealed compelling evidence that chimpanzees use gestures to communicate in a flexible, goal-oriented, and intentional fashion [6-8], replicated a...

Factors influencing the abilities of different animals to use cooperative social cues from humans are still unclear, in spite of long-standing interest in the topic. One of the few species that have been found successful at using human pointing is the African elephant (Loxodonta africana); despite few opportunities for learning about pointing, elep...

The ambiguity of the term ‘complex’ in studies of animal behaviour and cognition can lead to theoretical and methodological disputes, as there seems to be little common ground regarding the features thought to introduce complexity. Based on examples not only in human and nonhuman primates but also in some species of birds, we explore three dimensio...

The gestures of great apes display some of the features of human language; they are flexibly employed and are used with the intent to communicate; (Call & Tomasello, 2007). However, patterns of gesture distribution across sites do not show evidence of the formation of local cultures. These distribution patterns differ from those found in other manu...

Efficient space use is a critical challenge for animals relying on stationary resources. It is often difficult with purely observational methods to gain unambiguous insight into any ability of primates to manage and process spatial information. Investigating the visible signs of the decision processes underlying space use often leaves open importan...

Referential pointing is important in the development of language comprehension in the child and is often considered a uniquely human capacity. Nonhuman great apes do point in captivity, usually for a human audience, but this has been interpreted as an interaction pattern learned from human caretakers, not indicative of natural deictic ability. In c...

Many group-living mammals and birds give both contact and distress calls. Contact calls are thought to operate in maintaining group stability and cohesion; distress calls are thought to operate in soliciting help, often from relatives. Here we propose that a single call of black-and-gold howlers (Alouatta caraya) serves both needs, but differently...

Animal alarm calls can encode information about a predator's category, size, distance or threat level. In non-human primates, alarm calls typically refer to broad classes of disturbances, in some instances to specific predators. Here, we present the results of a field experiment with a New World primate, the black-fronted titi monkey (Callicebus ni...

How animals gain information from attending to the behavior of others has been widely studied, driven partly by the importance of referential pointing in human cognitive development [1-4], but species differences in reading human social cues remain unexplained. One explanation is that this capacity evolved during domestication [5, 6], but it may be...

Animal alarm calls can encode information about a predator's category, size, distance or threat level. In non-human primates, alarm calls typically refer to broad classes of disturbances, in some instances to specific predators. Here, we present the results of a field experiment with a New World primate, the black-fronted titi monkey (Callicebus ni...

We examined hand preference in the intentional gestural communication of wild chimpanzees in the Budongo forest, Uganda. Individuals showed some tendency to be lateralized, although less than has been reported for begging and pointing gestures in captivity; on average, their absolute bias was around 0.25 (where 1.0 represents complete right- or lef...

Variation in methods and measures, resulting in past dispute over the existence of population handedness in nonhuman great apes, has impeded progress into the origins of human right-handedness and how it relates to the human hallmark of language. Pooling evidence from behavioral studies, neuroimaging and neuroanatomy, we evaluate data on manual and...

Highlights ► Here we respond to Thornton & McAuliffe's Forum article (2012, Animal Behaviour, 83, e6–e9). ► The functional definition of animal teaching should not be the sole touchstone for publication on this topic. ► Within-subjects analyses are needed to identify cases in which teachers assist slow learners. ► More attention to cognitive underp...

Black-fronted titi monkeys, Callicebus nigrifrons, produce acoustically distinct vocalizations in response to several predator species. Compared to other primates, the calls are remarkably quiet, high-pitched and structurally simple, suggesting that they may not function uniquely as predator-specific warning calls. To address this, we investigated...

We describe the gestural communication of wild chimpanzees in the evolutionarily urgent context of consortship. Consortship represented the dominant context for the use of gestural communication by adult males in the Sonso community. Gesturing provided consorting males with the opportunity to communicate their intentions to the female, while avoidi...

Upon encountering predators, many animals produce specific vocalisations that alert others and sometimes dissuade the predators from hunting. Callicebus monkeys are known for their large vocal repertoire, but little is known about the function and meaning of most call types. We recorded a large number of natural predator responses from five differe...

This chapter reveals the nature of deceptive tactics as potential evidence of innovation in the social lives of individual primates. It suggests that primate tactical deception typically involves behaviour that is idiosyncratic to particular individuals, rather than species-or population-wide traits. As such, these tactics reflect innovation; altho...

This chapter examines the current evidence of intellectual skills in non-human primates for what their distribution across species shows about the evolutionary history of cognition. At the same time, it considers the theories of how this historical trajectory came about. It argues that the evidence indicates that several different selection pressur...

“Having a theory of mind” is often invoked to explain remarkable abilities in social cognition, but in reality this is little more than a re-description of the data, a challenge for theorists to understand what it really means, and how we—and perhaps some other species—evolved those abilities. I argue that these abilities most likely grew out of an...

Highlights ► We discuss limitations of Caro & Hauser’s (1992, Q. Rev. Biol., 67, 151–174) purely functional definition of teaching. ► We argue that intentional teaching better informs us about the evolution of distinctively human attributes. ► Research should focus on rare cases of knowledgeable individuals’ acts to correct deficiencies in slow lea...

Chimpanzees at Budongo, Uganda, regularly gesture in series, including 'bouts' of gesturing that include response waiting and 'sequences' of rapid-fire gesturing without pauses. We examined the distribution and correlates of 723 sequences and 504 bouts for clues to the function of multigesture series. Gesturing by older chimpanzees was more likely...

Great ape gestural communication is known to be intentional, elaborate and flexible; yet there is controversy over the best interpretation of the system and how gestures are acquired, perhaps because most studies have been made in restricted, captive settings. Here, we report the first systematic analysis of gesture in a population of wild chimpanz...

Elaborate manual skills of food processing are known in several species of great ape; but their manner of acquisition is controversial. Local, "cultural" traditions show the influence of social learning, but it is uncertain whether this includes the ability to imitate the organization of behavior. Dispute has centered on whether program-level imita...

Where a natural phenomenon can be brought under experimental control, either in the laboratory or the field, greater power of analysis is always achieved. But what of the phenomena that (so far) have not proved amenable to experiment? The answer for animal cognition has often been that analysis must

The sight of an animal making and using a tool captivates scientists and laymen alike, perhaps because it forces us to question some of our ideas about human uniqueness. Does the animal know how the tool works? Did it anticipate the need for the tool and make it in advance? To some, this fascination with tools seems arbitrary and anthropocentric; a...