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Uher, J., Asendorpf, J. B., & Call, J. (2008). Personality in the behaviour of great apes: temporal stability, cross-situational consistency and coherence in response. Anim. Behav., 75(1), 99–112.
Abstract: Using a multidisciplinary approach, the present study complements ethological behaviour measurements with basic theoretical concepts, methods and approaches of the personality psychological trait paradigm. Its adoptability and usefulness for animal studies are tested exemplarily on a sample of 20 zoo-housed great apes (five of each of the following species): bonobos, Pan paniscus; chimpanzees, Pan troglodytes verus; gorillas, Gorilla gorilla gorilla; and orang-utans, Pongo pygmaeus abelii. Data on 76 single trait-relevant behaviours were recorded in a series of 14 laboratory-based situations and in two different group situations. Data collection was repeated completely after a break of 2 weeks within a 60-day period. All behaviour records were sufficiently reliable. Individual- and variable-oriented analyses showed high/substantial temporal stability on different levels of aggregation. Distinctive and stable individual situational and response profiles clarified the importance of situations and of multiple trait-relevant behaviours. The present study calls for a closer collaboration between behavioural biologists and personality psychologists to tap the full potential of animal personality research.
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Herrmann, E., Call, J., Hernandez-Lloreda, M. V., Hare, B., & Tomasello, M. (2007). online material. Science, 317(5843), 1360–1366.
Abstract: Humans have many cognitive skills not possessed by their nearest primate relatives. The cultural intelligence hypothesis argues that this is mainly due to a species-specific set of social-cognitive skills, emerging early in ontogeny, for participating and exchanging knowledge in cultural groups. We tested this hypothesis by giving a comprehensive battery of cognitive tests to large numbers of two of humans' closest primate relatives, chimpanzees and orangutans, as well as to 2.5-year-old human children before literacy and schooling. Supporting the cultural intelligence hypothesis and contradicting the hypothesis that humans simply have more “general intelligence,” we found that the children and chimpanzees had very similar cognitive skills for dealing with the physical world but that the children had more sophisticated cognitive skills than either of the ape species for dealing with the social world.
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Herrmann, E., Call, J., Hernandez-Lloreda, M. V., Hare, B., & Tomasello, M. (2007). Humans Have Evolved Specialized Skills of Social Cognition: The Cultural Intelligence Hypothesis. Science, 317(5843), 1360–1366.
Abstract: Humans have many cognitive skills not possessed by their nearest primate relatives. The cultural intelligence hypothesis argues that this is mainly due to a species-specific set of social-cognitive skills, emerging early in ontogeny, for participating and exchanging knowledge in cultural groups. We tested this hypothesis by giving a comprehensive battery of cognitive tests to large numbers of two of humans' closest primate relatives, chimpanzees and orangutans, as well as to 2.5-year-old human children before literacy and schooling. Supporting the cultural intelligence hypothesis and contradicting the hypothesis that humans simply have more “general intelligence,” we found that the children and chimpanzees had very similar cognitive skills for dealing with the physical world but that the children had more sophisticated cognitive skills than either of the ape species for dealing with the social world.
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Bräuer, J., Call, J., & Tomasello, M. (2008). Chimpanzees do not take into account what others can hear in a competitive situation. Anim. Cogn., 11(1), 1435–9448.
Abstract: Chimpanzees (Pan troglodytes) know what others can and cannot see in a competitive situation. Does this reflect a general understanding the perceptions of others` In a study by Hare et al. (2000) pairs of chimpanzees competed over two pieces of food. Subordinate individuals preferred to approach food that was behind a barrier that the dominant could not see, suggesting that chimpanzees can take the visual perspective of others. We extended this paradigm to the auditory modality to investigate whether chimpanzees are sensitive to whether a competitor can hear food rewards being hidden. Results suggested that the chimpanzees did not take what the competitor had heard into account, despite being able to locate the hiding place themselves by the noise.
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Tomasello, M., & Call, J. (2006). Do chimpanzees know what others see ? or only what they are looking at? In M. Nudds, & S. Hurley (Eds.), Rational Animals? (pp. 371–384). Oxford: Oxford University Press.
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Call, J. (2003). Beyond learning fixed rules and social cues: abstraction in the social arena. Phil. Trans. Biol. Sci., 358(1435), 1189–1196.
Abstract: Abstraction is a central idea in many areas of physical comparative cognition such as categorization, numerical competence or problem solving. This idea, however, has rarely been applied to comparative social cognition. In this paper, I propose that the notion of abstraction can be applied to the social arena and become an important tool to investigate the social cognition and behaviour processes in animals. To make this point, I present recent evidence showing that chimpanzees know about what others can see and about what others intend. These data do not fit either low-level mechanisms based on stimulus-response associations or high-level explanations based on metarepresentational mechanisms such as false belief attribution. Instead, I argue that social abstraction, in particular the development of concepts such as seeing in others, is key to explaining the behaviour of our closest relative in a variety of situations.
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Kaminski, J., Call, J., & Tomasello, M. (2006). Goats' behaviour in a competitive food paradigm: Evidence for perspective taking? Behaviour, 143, 1341–1356.
Abstract: Many mammalian species are highly social, creating intra-group competition for such things as food and mates. Recent research with nonhuman primates indicates that in competitive situations individuals know what other individuals can and cannot see, and they use this knowledge to their advantage in various ways. In the current study, we extended these findings to a non-primate species, the domestic goat, using the conspecific competition paradigm developed by Hare et al. (2000). Like chimpanzees and some other nonhuman primates, goats live in fission-fusion societies, form coalitions and alliances, and are known to reconcile after fights. In the current study, a dominant and a subordinate individual competed for food, but in some cases the subordinate could see things that the dominant could not. In the condition where dominants could only see one piece of food but subordinates could see both, subordinates' preferences depended on whether they received aggression from the dominant animal during the experiment. Subjects who received aggression preferred the hidden over the visible piece of food, whereas subjects who never received aggression significantly preferred the visible piece. By using this strategy, goats who had not received aggression got significantly more food than the other goats. Such complex social interactions may be supported by cognitive mechanisms similar to those of chimpanzees. We discuss these results in the context of current issues in mammalian cognition and socio-ecology.
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Call, J., & Carpenter, M. (2001). Do apes and children know what they have seen? Anim. Cogn., 3(4), 207–220.
Abstract: Chimpanzees and young children understand much about what other individuals have and have not seen. This study investigates what they understand about their own visual perception. Chimpanzees, orangutans, and 2.5-year-old children were presented with a finding game in which food or stickers were hidden in one of two or three tubes. We varied whether subjects saw the baiting of the tubes, whether subjects could see through the tubes, and whether there was a delay between baiting and presentation of the tubes to subjects. We measured not only whether subjects chose the correct tube but also, more importantly, whether they spontaneously looked into one or more of the tubes before choosing one. Most apes and children appropriately looked into the tubes before choosing one more often when they had not seen the baiting than when they had seen the baiting. In general, they used efficient search strategies more often than insufficient or excessive ones. Implications of subjects' search patterns for their understanding of seeing and knowing in the self are discussed.
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Call, J., Agnetta, B., & Tomasello, M. (2000). Cues that chimpanzees do and do not use to find hidden objects. Anim. Cogn., 3(1), 23–34.
Abstract: Chimpanzees follow conspecific and human gaze direction reliably in some situations, but very few chimpanzees reliably use gaze direction or other communicative signals to locate hidden food in the object-choice task. Three studies aimed at exploring factors that affect chimpanzee performance in this task are reported. In the first study, vocalizations and other noises facilitated the performance of some chimpanzees (only a minority). In the second study, various behavioral cues were given in which a human experimenter either touched, approached, or actually lifted and looked under the container where the food was hidden. Each of these cues led to enhanced performance for only a very few individuals. In the third study – a replication with some methodological improvements of a previous experiment – chimpanzees were confronted with two experimenters giving conflicting cues about the location of the hidden food, with one of them (the knower) having witnessed the hiding process and the other (the guesser) not. In the crucial test in which a third experimenter did the hiding, no chimpanzee found the food at above chance levels. Overall, in all three studies, by far the best performers were two individuals who had been raised in infancy by humans. It thus seems that while chimpanzees are very good at “behavior reading” of various sorts, including gaze following, they do not understand the communicative intentions (informative intentions) behind the looking and gesturing of others – with the possible exception of enculturated chimpanzees, who still do not understand the differential significance of looking and gesturing done by people who have different knowledge about states of affairs in the world.
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Call, J., Hare, B. A., & Tomasello, M. (1998). Chimpanzee gaze following in an object-choice task. Anim. Cogn., 1(2), 89–99.
Abstract: Many primate species reliably track and follow the visual gaze of conspecifics and humans, even to locations above and behind the subject. However, it is not clear whether primates follow a human's gaze to find hidden food under one of two containers in an object-choice task. In a series of experiments six adult female chimpanzees followed a human's gaze (head and eye direction) to a distal location in space above and behind them, and checked back to the human's face when they did not find anything interesting or unusual. This study also assessed whether these same subjects would also use the human's gaze in an object-choice task with three types of occluders: barriers, tubes, and bowls. Barriers and tubes permitted the experimenter to see their contents (i.e., food) whereas bowls did not. Chimpanzees used the human's gaze direction to choose the tube or barrier containing food but they did not use the human's gaze to decide between bowls. Our findings allowed us to discard both simple orientation and understanding seeing-knowing in others as the explanations for gaze following in chimpanzees. However, they did not allow us to conclusively choose between orientation combined with foraging tendencies and understanding seeing in others. One interesting possibility raised by these results is that studies in which the human cannot see the reward at the time of subject choice may potentially be underestimating chimpanzees' social knowledge.
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