Although chimpanzees have been reported to understand to some extent others’ visual perception, previous studies using food requesting tasks are divided on whether or not chimpanzees understand the role of eye gaze. One plausible reason for this discrepancy may be the familiarity of the testing situation. Previous food requesting tasks with negative results used an unfamiliar situation that may be difficult for some chimpanzees to recognize as a requesting situation, whereas those with positive results used a familiar (...) situation. The present study tested chimpanzees’ understanding of others’ attentional states by comparing two requesting situations: an unfamiliar situation in which food was put on a table, and a familiar situation in which chimpanzees requested food held by an experimenter. Chimpanzees showed evidence of understanding the experimenter’s attentional variations and the role of eye gaze only in the latter task. This suggests that an unfamiliar requesting situation may keep subjects from expressing their understanding of others’ attentional states even though they are sensitive to them. Keywords: Understanding attention; Social cognition; Chimpanzees. (shrink)

Imitation recognition provides a viable platform from which advanced social cognitive skills may develop. Despite evidence that non-human primates are capable of imitation recognition, how this ability is related to social cognitive skills is unknown. In this study, we compared imitation recognition performance, as indicated by the production of testing behaviors, with performance on a series of tasks that assess social and physical cognition in 49 chimpanzees. In the initial analyses, we found that males were more responsive than females (...) to being imitated and engaged in significantly greater behavior repetitions and testing sequences. We also found that subjects who consistently recognized being imitated performed better on social but not physical cognitive tasks, as measured by the Primate Cognitive Test Battery. These findings suggest that the neural constructs underlying imitation recognition are likely associated with or among those underlying more general socio-communicative abilities in chimpanzees. Implications regarding how imitation recognition may facilitate other social cognitive processes, such as mirror self-recognition, are discussed. (shrink)

Honest signalling theory suggests that humans and chimpanzees can extract socially relevant information relating to personality from the faces of their conspecifics. Humans are also able to extract information from chimpanzees’ faces. Here, we examine whether personality characteristics of chimpanzees, including measures of psychopathy, can be discerned based purely on facial morphology in photographs. Twenty-one chimpanzees were given naïve and expert personality ratings on the Ten Item Personality Inventory (TIPI) and the Chimpanzee Triarchic Model of Psychopathy (...) (CHMP-Tri) before and following behavioural observations. Characteristics relating to openness, conscientiousness, extraversion, and disinhibition could be distinguished from the faces of chimpanzees. Individuals higher on disinhibition have lower scores on conscientiousness and emotional stability and higher scores on extraversion, while those higher on meanness have lower conscientiousness and agreeableness. Facial expressions are linked to personality traits present in the TIPI and CHMP-Tri models: the Relaxed Face and the Grooming Face were displayed more by chimpanzees higher on agreeableness, whereas the Compressed Lips Face was observed more in those individuals higher on boldness, and the Full Open Grin was displayed more by chimpanzees higher on extraversion but lower on emotional stability and conscientiousness. Facial expressions were also found to be associated with particular behavioural contexts, namely the Grooming Face in affiliative contexts and the Relaxed and Relaxed Open Mouth Faces in neutral contexts. Dominant chimpanzees display higher levels of boldness and more Compressed Lips Faces, Relaxed Open Mouth Faces, and Grooming Faces than subordinate individuals. These findings support and extend evidence for an honest signalling system and a personality structure shared between humans and chimpanzees. Future research could further explore how personality is conveyed through the face, perhaps through more than just singular aspects of character, and maybe reflecting what chimpanzees themselves are able to do. (shrink)

Speech act theory describes units of language as acts which function to change the behavior or beliefs of the partner. Therefore, with every utterance an individual seeks a communicative goal that is the underlying motive for the utterance’s production; this is the utterance’s function. Studies of deaf and hearing human children classify utterances into categories of communicative function. This study classified signing chimpanzees’ utterances into the categories used in human studies. The chimpanzees utilized all seven categories of communicative (...) functions and used them in ways that resembled human children. The chimpanzees’ utterances functioned to answer questions, request objects and actions, describe objects and events, make statements about internal states, accomplish tasks such as initiating games, protest interlocutor behavior, and as conversational devices to maintain and initiate conversation. (shrink)

Clique sizes for chimpanzee (Pan troglodytes) grooming and for human conversation are compared in order to test Robin Dunbar’s hypothesis that human language is almost three times as efficient a bonding mechanism as primate grooming. Recalculation of the data provided by Dunbar et al. (1995) reveals that the average clique size for human conversation is 2.72 whereas that of chimpanzee grooming is shown to be 2.18. The efficiency of human conversation and actual chimpanzee grooming over Dunbar’s primate grooming model (...) (always one-to-one and a one-way interaction) is 1.27 and 1.25, respectively, when we take role alternation into account. Chimpanzees can obtain about the same efficiency as humans in terms of quantity of social interactions because their grooming is often mutual and polyadic. (shrink)

The completion of the chimpanzee genome will greatly help us determine which genetic changes are unique to humanity. Chimpanzees are our closest living relative, and a recent study has made considerable progress towards decoding the genome of our sister taxon.1 Over 75,000 common chimpanzee (Pan troglodytes) bacterial artificial chromosome end sequences were aligned and mapped to the human genome. This study shows the remarkable genetic similarity (98.77%) between humans and chimpanzees, while highlighting intriguing areas of potential difference. (...) If we wish to understand the genetic basis of humankind, the completion of the chimpanzee genome deserves high priority. BioEssays 24:490–493, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

This chapter compares the social behaviour of human hunter-gatherers with that of the better-studied chimpanzee species, Pan troglodytes, in an attempt to pinpoint the unique features of human social evolution. Although hunter-gatherers and chimpanzees living in central Africa have similar body weights, humans live at much lower population densities due to their greater dependence on predation. Human foraging parties have longer duration than those of chimpanzees, lasting hours rather than minutes, and a higher level of mutual dependence, (...) through the division of labour between men and women ; which is in turn related to pair-bonding, and meat sharing to reduce the risk of individual hunters' failure on any particular day. The band appears to be a uniquely human social unit that resolves the tension between greater dispersion and greater interdependence. (shrink)

Conversational interactions depend on partners making contingent responses. This experiment examined the responses of five chimpanzees, Washoe, Moja, Tatu, Dar and Loulis, to four conversational conditions. Following the chimpanzee’s request, a human interlocutor either: complied with the request, provided an unrequested item or activity, refused to comply or did not respond to the request. The chimpanzees’ responses were contingent on the conversational input of the interlocutor. When their requests were satisfied, the chimpanzees most often ceased signing. However, (...) when their requests were misunderstood, refused or not acknowledged, the chimpanzees repeated and revised. This pattern of responses is comparable to patterns of conversational responses in human children. Keywords: chimpanzees; American Sign Language; requests; pragmatics; conversation; gesture; communication; Pan troglodytes. (shrink)

For acquired behaviour to count as cultural, two conditions must be met: it must propagate in a social group, and it must remain stable across generations in the process of propagation. It is commonly assumed that imitation is the mechanism that explains both the spread of animal culture and its stability. We review the literature on transmission chain studies in chimpanzees (Pan troglodytes) and other animals, and we use a formal model to argue that imitation, which may well (...) play a major role in the propagation of animal culture, cannot be considered faithful enough to explain its stability. We consider the contribution that other psychological and ecological factors might make to the stability of animal culture observed in the wild. (shrink)

Cross-species comparisons are benefited by compatible datasets; conclusions related to phylogenetic comparisons, questions on convergent and divergent evolution, or homologs versus analogs can only be made when the behaviors being measured are comparable. A direct comparison of the social function of physical contact across two disparate taxa is possible only if data collection and analyses methodologies are analogous. We identify and discuss the parameters, assumptions and measurement schemes applicable to multiple taxa and species that facilitate cross-species comparisons. To illustrate our (...) proposed guidelines for evaluating the role played by tactile contact in social behavior across disparate taxa, this paper presents data on mother-offspring relationships in the two species studied by the authors: chimpanzees (Pan troglodytes schweinfurthii) and dolphins (bottlenose and spotted, Tursiops truncatus and Stenella frontalis, respectively). Cross-species comparative studies allow for a more comprehensive assessment of the similarities and differences with respect to how animals traverse the relationships that form their social groups and societies. (shrink)