Abstract: Abstract  The issue whether non-human primates have other-regarding preference and/or inequity aversion has been under debate. We investigated whether tufted capuchin monkeys are sensitive to others’ reward in various experimental food sharing settings. Two monkeys faced each other. The operator monkey chose one of two food containers placed between the participants, each containing a food item for him/herself and another for the recipient. The recipient passively received either high- or low-value food depending on the operator’s choice, whereas the operator obtained the same food regardless of his/her choice. The recipients were either the highest- or lowest-ranking member of the group, and the operators were middle-ranking. In Experiment 1, the operators chose the high-value food for the subordinate recipient more frequently than when there was no recipient, whereas they were indifferent in their choice for the dominant. This differentiated behavior could have been because the dominant recipient frequently ate the low-value food. In Experiment 2, we increased the difference in the value of the two food items so that both recipients would reject the low-value food. The results were the same as in Experiment 1. In Experiment 3, we placed an opaque screen in front of the recipient to examine effects of visual contact between the participants. The operators’ food choice generally shifted toward providing the low-value food for the recipient. These results suggest that capuchins are clearly sensitive to others’ reward and that they show other-regarding preference or a form of inequity aversion depending upon the recipients and the presence of visual contact.

Abstract: In the bidirectional control procedure, observers are exposed to a conspecific demonstrator responding to a manipulandum in one of two directions (e.g., left vs. right). This procedure controls for socially mediated effects (the mere presence of a conspecific) and stimulus enhancement (attention drawn to a manipulandum by its movement), and it has the added advantage of being symmetrical (the two different responses are similar in topography). Imitative learning is demonstrated when the observers make the response in the direction that they observed it being made. Recently, however, it has been suggested that when such evidence is found with a predominantly olfactory animal, such as the rat, it may result artifactually from odor cues left on one side of the manipulandum by the demonstrator. In the present experiment, we found that Japanese quail, for which odor cues are not likely to play a role, also showed significant correspondence between the direction in which the demonstrator and the observer push a screen to gain access to reward. Furthermore, control quail that observed the screen move, when the movement of the screen was not produced by the demonstrator, did not show similar correspondence between the direction of screen movement observed and that performed by the observer. Thus, with the appropriate control, the bidirectional procedure appears to be useful for studying imitation in avian species.

Abstract: Chimpanzee (Pan troglodytes) societies are typically characterized as physically aggressive, male-bonded and male-dominated. Their close relatives, the bonobos (Pan paniscus), differ in startling and significant ways. For instance, female bonobos bond with one another, form coalitions, and dominate males. A pattern of reluctance to consider, let alone acknowledge, female dominance in bonobos exists, however. Because both species are equally “man's” closest relative, the bonobo social system complicates models of human evolution that have historically been based upon referents that are male and chimpanzee-like. The bonobo evidence suggests that models of human evolution must be reformulated such that they also accommodate: real and meaningful female bonds; the possibility of systematic female dominance over males; female mating strategies which encompass extra-group paternities; hunting and meat distribution by females; the importance of the sharing of plant foods; affinitive inter-community interactions; males that do not stalk and attack and are not territorial; and flexible social relationships in which philopatry does not necessarily predict bonding pattern.

Abstract: Historically, a dichotomy has been drawn between the semantic communication of human language and the apparently emotional calls of animals. Current research paints a more complicated picture. Just as scientists have identified elements of human speech that reflect a speaker's emotions, field experiments have shown that the calls of many animals provide listeners with information about objects and events in the environment. Like human speech, therefore, animal vocalizations simultaneously provide others with information that is both semantic and emotional. In support of this conclusion, we review the results of field experiments on the natural vocalizations of African vervet monkeys, diana monkeys, baboons, and suricates (a South African mongoose). Vervet and diana monkeys give acoustically distinct alarm calls in response to the presence of leopards, eagles, and snakes. Each alarm call type elicits a different, adaptive response from others nearby. Field experiments demonstrate that listeners compare these vocalizations not just according to their acoustic properties but also according to the information they convey. Like monkeys, suricates give acoustically distinct alarm calls in response to different predators. Within each predator class, the calls also differ acoustically according to the signaler's perception of urgency. Like speech, therefore, suricate alarm calls convey both semantic and emotional information. The vocalizations of baboons, like those of many birds and mammals, are individually distinctive. As a result, when one baboon hears a sequence of calls exchanged between two or more individuals, the listener acquires information about social events in its group. Baboons, moreover, are skilled “eavesdroppers:” their response to different call sequences provides evidence of the sophisticated information they acquire from other individuals' vocalizations. Baboon males give loud “wahoo” calls during competitive displays. Like other vocalizations, these highly emotional calls provide listeners with information about the caller's dominance rank, age, and competitive ability. Although animal vocalizations, like human speech, simultaneously encode both semantic and emotional information, they differ from language in at least one fundamental respect. Although listeners acquire rich information from a caller's vocalization, callers do not, in the human sense, intend to provide it. Listeners acquire information as an inadvertent consequence of signaler behavior.

Abstract: Research on nonhuman primates has produced compelling evidence for reconciliation and consolation, that is, postconflict contacts that serve to respectively repair social relationships and reassure distressed individuals, such as victims of attack. This has led to a view of conflict and conflict resolution as an integrated part of social relationships, hence determined by social factors and modifiable by the social environment. Implications of this new model of social conflict are discussed along with evidence for behavioral flexibility, the value of cooperation, and the possibility that distress alleviation rests on empathy, a capacity that may be present in chimpanzees and humans but not in most other animals.