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Fuentes, A., Malone, N., Sanz, C., Matheson, M., & Vaughan, L. (2002). Conflict and post-conflict behavior in a small group of chimpanzees. Primates, 43(3), 223–235.
Abstract: Chimpanzee research plays a central role in the discussions of conflict negotiation. Reconciliation, or the attraction and affiliation of former opponents following conflict, has been proposed as a central element of conflict negotiation in chimpanzees and various other taxa. In an attempt to expand the database of chimpanzee conflict resolution, conflict and post-conflict behavior were recorded for a small group of socially housed chimpanzees at the Chimpanzee and Human Communication Institute, at Central Washington University. Data were collected over six 6-week periods between 1997 and 2000, for a total of 840 hours of observation, resulting in a substantial post-conflict (PC) and matched control (MC) data set. The data demonstrate this group's tendencies to maintain visual contact and closer proximity after conflicts. Dyadic corrected conciliatory tendencies ranged between 0 – 37.5% and averaged 17.25% across all dyads. Individual corrected conciliatory tendencies ranged between 5.8 and 32%. The results of this study combined with recent publications on captive and free-ranging chimpanzee post-conflict behavior suggest that variation in post-conflict behavior may be important to our understanding of chimpanzee conflict negotiation, and may also have implications for the design and management of captive chimpanzee enclosures and social groups, respectively.
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Gallup, G. G. J. (1985). Do minds exist in species other than our own? Neurosci Biobehav Rev, 9(4), 631–641.
Abstract: An answer to the question of animal awareness depends on evidence, not intuition, anecdote, or debate. This paper examines some of the problems inherent in an analysis of animal awareness, and whether animals might be aware of being aware is offered as a more meaningful distinction. A framework is presented which can be used to make a determination about the extent to which other species have experiences similar to ours based on their ability to make inferences and attributions about mental states in others. The evidence from both humans and animals is consistent with the idea that the capacity to use experience to infer the experience of others is a byproduct of self-awareness.
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Hare, B., Brown, M., Williamson, C., & Tomasello, M. (2002). The domestication of social cognition in dogs. Science, 298(5598), 1634–1636.
Abstract: Dogs are more skillful than great apes at a number of tasks in which they must read human communicative signals indicating the location of hidden food. In this study, we found that wolves who were raised by humans do not show these same skills, whereas domestic dog puppies only a few weeks old, even those that have had little human contact, do show these skills. These findings suggest that during the process of domestication, dogs have been selected for a set of social-cognitive abilities that enable them to communicate with humans in unique ways.
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Hayashi, M. (2007). Stacking of blocks by chimpanzees: developmental processes and physical understanding. Anim. Cogn., 10(2), 89–103.
Abstract: The stacking-block task has been used to assess cognitive development in both humans and chimpanzees. The present study reports three aspects of stacking behavior in chimpanzees: spontaneous development, acquisition process following training, and physical understanding assessed through a cylindrical-block task. Over 3 years of longitudinal observation of block manipulation, one of three infant chimpanzees spontaneously started to stack up cubic blocks at the age of 2 years and 7 months. The other two infants began stacking up blocks at 3 years and 1 month, although only after the introduction of training by a human tester who rewarded stacking behavior. Cylindrical blocks were then introduced to assess physical understanding in object-object combinations in three infant (aged 3-4) and three adult chimpanzees. The flat surfaces of cylinders are suitable for stacking, while the rounded surface is not. Block manipulation was described using sequential codes and analyzed focusing on failure, cause, and solution in the task. Three of the six subjects (one infant and two adults) stacked up cylindrical blocks efficiently: frequently changing the cylinders' orientation without contacting the round side to other blocks. Rich experience in stacking cubes may facilitate subjects' stacking of novel, cylindrical shapes from the beginning. The other three subjects were less efficient in stacking cylinders and used variable strategies to achieve the goal. Nevertheless, they began to learn the effective way of stacking over the course of testing, after about 15 sessions (75 trials).
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Hayashi, M., & Matsuzawa, T. (2003). Cognitive development in object manipulation by infant chimpanzees. Anim. Cogn., 6(4), 225–233.
Abstract: This study focuses on the development of spontaneous object manipulation in three infant chimpanzees during their first 2 years of life. The three infants were raised by their biological mothers who lived among a group of chimpanzees. A human tester conducted a series of cognitive tests in a triadic situation where mothers collaborated with the researcher during the testing of the infants. Four tasks were presented, taken from normative studies of cognitive development of Japanese infants: inserting objects into corresponding holes in a box, seriating nesting cups, inserting variously shaped objects into corresponding holes in a template, and stacking up wooden blocks. The mothers had already acquired skills to perform these manipulation tasks. The infants were free to observe the mothers' manipulative behavior from immediately after birth. We focused on object-object combinations that were made spontaneously by the infant chimpanzees, without providing food reinforcement for any specific behavior that the infants performed. The three main findings can be summarized as follows. First, there was precocious appearance of object-object combination in infant chimpanzees: the age of onset (8-11 months) was comparable to that in humans (around 10 months old). Second, object-object combinations in chimpanzees remained at a low frequency between 11 and 16 months, then increased dramatically at the age of approximately 1.5 years. At the same time, the accuracy of these object-object combinations also increased. Third, chimpanzee infants showed inserting behavior frequently and from an early age but they did not exhibit stacking behavior during their first 2 years of life, in clear contrast to human data.
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Herrmann, E., Melis, A. P., & Tomasello, M. (2006). Apes' use of iconic cues in the object-choice task. Anim. Cogn., 9(2), 118–130.
Abstract: In previous studies great apes have shown little ability to locate hidden food using a physical marker placed by a human directly on the target location. In this study, we hypothesized that the perceptual similarity between an iconic cue and the hidden reward (baited container) would help apes to infer the location of the food. In the first two experiments, we found that if an iconic cue is given in addition to a spatial/indexical cue – e.g., picture or replica of a banana placed on the target location – apes (chimpanzees, bonobos, orangutans, gorillas) as a group performed above chance. However, we also found in two further experiments that when iconic cues were given on their own without spatial/indexical information (iconic cue held up by human with no diagnostic spatial/indexical information), the apes were back to chance performance. Our overall conclusion is that although iconic information helps apes in the process of searching hidden food, the poor performance found in the last two experiments is due to apes' lack of understanding of the informative (cooperative) communicative intention of the experimenter.
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Hirata, S. (2007). A note on the responses of chimpanzees (Pan troglodytes) to live self-images on television monitors. Behav. Process., 75(1), 85–90.
Abstract: The majority of studies on self-recognition in animals have been conducted using a mirror as the test device; little is known, however, about the responses of non-human primates toward their own images in media other than mirrors. This study provides preliminary data on the reactions of 10 chimpanzees to live self-images projected on two television monitors, each connected to a different video camera. Chimpanzees could see live images of their own faces, which were approximately life-sized, on one monitor. On the other monitor, they could see live images of their whole body, which were approximately one-fifth life-size, viewed diagonally from behind. In addition, several objects were introduced into the test situation. Out of 10 chimpanzees tested, 2 individuals performed self-exploratory behaviors while watching their own images on the monitors. One of these two chimpanzees successively picked up two of the provided objects in front of a monitor, and watched the images of these objects on the monitor. The results indicate that these chimpanzees were able to immediately recognize live images of themselves or objects on the monitors, even though several features of these images differed from those of their previous experience with mirrors.
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Hirata, S., & Celli, M. L. (2003). Role of mothers in the acquisition of tool-use behaviours by captive infant chimpanzees. Anim. Cogn., 6(4), 235–244.
Abstract: This article explores the maternal role in the acquisition of tool-use behaviours by infant chimpanzees ( Pan troglodytes). A honey-fishing task, simulating ant/termite fishing found in the wild, was introduced to three dyads of experienced mother and naive infant chimpanzees. Four fishing sites and eight sets of 20 objects to be used as tools, not all appropriate, were available. Two of the mothers constantly performed the task, using primarily two kinds of tools; the three infants observed them. The infants, regardless of the amount of time spent observing, successfully performed the task around the age of 20-22 months, which is earlier than has been recorded in the wild. Two of the infants used the same types of tools that the adults predominantly used, suggesting that tool selectivity is transmitted. The results also show that adults are tolerant of infants, even if unrelated; infants were sometimes permitted to lick the tools, or were given the tools, usually without honey, as well as permitted to observe the adult performances closely.
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Hopkins, W. D., & Washburn, D. A. (2002). Matching visual stimuli on the basis of global and local features by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). Anim. Cogn., 5(1), 27–31.
Abstract: This study was designed to examine whether chimpanzees and monkeys exhibit a global-to-local precedence in the processing of hierarchically organized compound stimuli, as has been reported for humans. Subjects were tested using a sequential matching-to-sample paradigm using stimuli that differed on the basis of their global configuration or local elements, or on both perceptual attributes. Although both species were able to discriminate stimuli on the basis of their global configuration or local elements, the chimpanzees exhibited a global-to-local processing strategy, whereas the rhesus monkeys exhibited a local-to-global processing strategy. The results suggest that perceptual and attentional mechanisms underlying information-processing strategies may account for differences in learning by primates.
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Hopkins, W. D., Taglialatela, J. P., & Leavens, D. A. (2007). Chimpanzees differentially produce novel vocalizations to capture the attention of a human. Anim. Behav., 73(2), 281–286.
Abstract: Chimpanzees, Pan troglodytes, produce numerous species-atypical signals when raised in captivity. We examined contextual elements of the use of two of these vocal signals, the `raspberry' and the extended grunt. Our results demonstrate that these vocalizations are not elicited by the presence of food, but instead function as attention-getting signals. These findings reveal a heretofore underappreciated category of animal signals: attention-getting sounds produced in novel environmental circumstances. The invention and use of species-atypical signals, considered in relation to group differences in signalling repertoires in apes in their natural habitats, may index a generative capacity in these hominoid species without obvious corollary in other primate species.
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