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Consolation, that is, postconflict affiliative contact by a bystander toward a recipient of aggression, has acquired an important role in the debate about empathy in great apes because it has been proposed that the reassuring behavior aimed at distressed parties reflects empathetic arousal. However, the function of this behavior is not fully understood. The present study tests specific predictions about the identity of bystanders on the basis of a database of 1102 agonistic interactions and their corresponding postconflict periods in two outdoor-housed groups of captive chimpanzees (Pan troglodytes). We found that recipients of aggression were more likely to be contacted by their own 'friends' than by 'friends' of the aggressor and that frequent targets of aggression were not more likely to offer consolation than were nontargets of aggression. These findings support the stress reduction hypothesis rather than two proposed alternatives, that is, the opponent relationship repair hypothesis and the self-protection hypothesis. Our results provide further support for relationship quality as a fundamental underlying factor explaining variation in the occurrence of consolation. Keywords: consolation, postconflict behavior, chimpanzees, Pan troglodytes, relationship quality DOI: 10.1037/a0019144

Chimpanzees are known to spontaneously provide contact comfort to recent victims of aggression, a behavior known as consolation. Similar behavior in human children is attributed to empathic or sympathetic concern. In line with this empathy hypothesis, chimpanzee consolation has been shown to reduce the recipient's state of arousal, hence to likely alleviate distress. Other predictions from the empathy hypothesis have rarely been tested, however, owing to small sample sizes in previous studies. An exceptionally large database of spontaneous consolation in two outdoor-housed groups of chimpanzees lends further support to the empathy hypothesis in that consolation occurred disproportionally between individuals that are socially close (i.e., kin and affiliation partners) and was more typical of females than males, which differences are also known of human empathy. These effects were demonstrated using generalized linear mixed models, which control multiple variables at once. An exception to the above pattern was formed by the highest-ranking males, which frequently offered consolation to victims of aggression, probably as part of their general policing function in chimpanzee society. Consolation occurred more frequently in the absence of reconciliation between former opponents, suggesting that actors are sensitive to the contact need of victims of aggression, which may be greater if the aggressor ignores them. That consolation is an integrated part of close mutual relationships is supported by the tendency for it being reciprocated. empathy | Pan troglodytes | postconflict affiliation doi/10.1073/pnas.1006991107

In the last two decades, it became largely accepted that monkeys show little, if any, copying fidelity. However, some recent studies have begun to challenge this notion. To explore reasons for such contrary findings, we designed a foraging apparatus so that in each of two experiments with capuchin monkeys (Cebus apella), a model would demonstrate one of two alternative methods to obtain food. The apparatus had a V-shaped track on which a panel could be slid up left or right from the center to reveal food. In Experiment 1, food was located in a cup directly behind the center panel. In Experiment 2, sliding the panel left or right revealed food either in left or right ends of the V-track. Since this sliding movement led directly to one food location exclusive of the other, we predicted capuchins would show greater copying fidelity in this second Experiment. Instead, subjects were significantly more faithful to the model's method in Experiment 1, which provided strong evidence of capuchins copying what they had observed. We suggest that the contrasting results of Experiment 1 may have occurred because capuchins prioritize exploratory behavior when alternative foraging locations are accessible. Keywords: social learning, social learning strategies, copying fidelity, traditions, capuchin, Cebus apella DOI: 10.1037/a0018005

Nonhuman primates posses a highly developed capacity for face recognition, which resembles the human capacity both cognitively and neurologically. Face recognition is typically tested by having subjects compare facial images, whereas there has been virtually no attention to how they connect these images to reality. Can nonhuman primates recognize familiar individuals in photographs? Such facial identification was examined in brown or tufted capuchin monkeys (Cebus apella), a New World primate, by letting subjects categorize facial images of conspecifics as either belonging to the in-group or out-group. After training on an oddity task with four images on a touch screen, subjects correctly identified one in-group member as odd among three out-group members, and vice versa. They generalized this knowledge to both new images of the same individuals and images of juveniles never presented before, thus suggesting facial identification based on real-life experience with the depicted individuals. This ability was unexplained by potential color cues because the same results were obtained with grayscale images. These tests demonstrate that capuchin monkeys, like humans, recognize whom they see in a picture. face recognition | individual discrimination | oddity | primate | visual discrimination doi/10.1073/pnas.0912174106

Primates live in complex social groups that necessitate recognition of the individuals with whom they interact. In humans, faces provide a visual means by which to gain information such as identity, allowing us to distinguish between both familiar and unfamiliar individuals. The current study used a computerized oddity task to investigate whether a New World primate, Cebus apella, can discriminate the faces of In-group and Out-group conspecifics based on identity. The current study, improved on past methodologies, demonstrates that capuchins recognize the faces of both familiar and unfamiliar conspecifics. Once a performance criterion had been reached, subjects successfully transferred to a large number of novel images within the first 100 trials thus ruling out performance based on previous conditioning. Capuchins can be added to a growing list of primates that appear to recognize two-dimensional facial images of conspecifics. Keywords: primates, cognition, oddity, visual discrimination

Helping and sharing among humans is often motivated by empathy and accompanied by a sense of satisfaction. To determine whether similar self-rewarding mechanisms may underpin assistance among nonhuman primates, eight female brown capuchin monkeys (Cebus apella) underwent testing in a simple choice paradigm. Paired with a partner, subjects could select either a 'selfish' option that rewarded only themselves, or a 'prosocial' option that rewarded both of them. Subjects systematically favored the prosocial option provided their partner was a) familiar, b) visible, and c) receiving rewards of equal value. Prosocial tendencies increased with social closeness, being lowest toward strangers and highest toward kin. That the monkeys understood the options was suggested by greater orientation to the partner during prosocial than selfish choices. Prosocial preferences were reduced by inequity, when the partner received a superior reward. If the view between both monkeys was blocked, choices became strikingly selfish. Thus, under certain conditions, delivering benefits to others seems gratifying to nonhuman primates. altruism | capuchin monkey | empathy | inequity | prosocial behavior

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.07.006 Byline: Bernard Thierry, Filippo Aureli, Charles L. Nunn, Odile Petit, Christophe Abegg, Frans B.M. de Waal Abstract: Conflict resolution is an essential component of primate sociality that has been studied extensively within primate social groups, but few studies have examined how conflict resolution behaviours covary at evolutionary scales. We assembled a standardized data set on social interactions of sexually mature females to analyse patterns of conflict resolution in 15 groups of nine macaque species. Between-group comparisons revealed no significant difference in nonkin reconciliation levels between groups of the same species, whereas substantial interspecific differences were found. We tested for associations between four behavioural traits involving reconciliation and dominance asymmetry that play a central role in primate social systems. Regression analyses using group values indicated that these traits (conciliatory tendencies, proportions of explicit reconciliatory contacts, kin bias and levels of counteraggression) exist as an integrated suite of characters. We found strong phylogenetic signal in most traits, which further indicates that they evolved during the adaptive radiation of macaques. Using the method of independent contrasts, relationships between conciliatory tendencies and proportions of explicit reconciliatory contacts and between kin bias and levels of counteraggression remained consistent after controlling for phylogeny. This reveals that evolutionary change in one trait leads to correlated changes in other traits. Collectively, these results show how comparative studies of detailed behavioural interactions can be used to elucidate primate socioecology. Author Affiliation: (a) Departement Ecologie, Physiologie & Ethologie, IPHC, Centre National pour la Recherche Scientifique, Universite Louis Pasteur, Strasbourg, France (a ) Research Centre in Evolutionary Anthropology and Palaeoecology, School of Biological & Earth Sciences, Liverpool John Moores University, U.K. (a ) Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig Germany (As.) Department of Integrative Biology, University of California, Berkeley, U.S.A. (aa) Living Links, Yerkes National Primate Research Center & Department of Psychology, Emory University, Atlanta, U.S.A. Article History: Received 24 May 2006; Revised 10 August 2006; Accepted 9 July 2007 Article Note: (miscellaneous) MS. number: 8978R

Without joint benefits, joint actions could never have evolved. Cooperative animals need to monitor closely how large a share they receive relative to their investment toward collective goals. This work documents the sensitivity to reward division in brown, or tufted, capuchin monkeys (Cebus apella). In addition to confirming previous results with a larger subject pool, this work rules out several alternative explanations and adds data on effort sensitivity. Thirteen adult monkeys exchanged tokens for rewards, showing negative reactions to receiving a less-favored reward than their partner. Because their negative reaction could not be attributed to the mere visibility of better rewards (greed hypothesis) nor to having received such rewards in the immediate past (frustration hypothesis), it must have been caused by seeing their partner obtain the better reward. Effort had a major effect in that by far the lowest level of performance in the entire study occurred in subjects required to expend a large effort while at the same time seeing their partner receive a better reward. It is unclear whether this effort-effect was based on comparisons with the partner, but it added significantly to the intensity of the inequity response. These effects are as expected if the inequity response evolved in the context of cooperative survival strategies. capuchin monkey | Cebus apella | cooperation | frustration | fairness

The natural communication of apes may hold clues about language origins, especially because apes frequently gesture with limbs and hands, a mode of communication thought to have been the starting point of human language evolution. The present study aimed to contrast brachiomanual gestures with orofacial movements and vocalizations in the natural communication of our closest primate relatives, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). We tested whether gesture is the more flexible form of communication by measuring the strength of association between signals and specific behavioral contexts, comparing groups of both the same and different ape species. Subjects were two captive bonobo groups, a total of 13 individuals, and two captive chimpanzee groups, a total of 34 individuals. The study distinguished 31 manual gestures and 18 facial/vocal signals. It was found that homologous facial/vocal displays were used very similarly by both ape species, yet the same did not apply to gestures. Both within and between species gesture usage varied enormously. Moreover, bonobos showed greater flexibility in this regard than chimpanzees and were also the only species in which multimodal communication (i.e., combinations of gestures and facial/vocal signals) added to behavioral impact on the recipient. bonobo | chimpanzee | communication | multimodal

The food collection and food consumption in pairs of brown capuchin monkeys (Cebus apella) presented with unequally valued foods, but without any task performance are analyzed. Analysis shows that equity or inequity plays a different role if food is served as a reward for a task rather than if it is simply made available for consumption.

Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus 'mark test' for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation. cognition | mirror self-recognition | theory of mind | intelligence | empathy

Observational studies of wild chimpanzees (Pan troglodytes) have revealed population-specific differences in behavior, thought to represent cultural variation. Field studies have also reported behaviors indicative of cultural learning, such as close observation of adult skills by infants, and the use of similar foraging techniques within a population over many generations. Although experimental studies have shown that chimpanzees are able to learn complex behaviors by observation, it is unclear how closely these studies simulate the learning environment found in the wild. In the present study we have used a diffusion chain paradigm, whereby a behavior is passed from one individual to the next in a linear sequence in an attempt to simulate intergenerational transmission of a foraging skill. Using a powerful three-group, two-action methodology, we found that alternative methods used to obtain food from a foraging device ('lift door' versus 'slide door') were accurately transmitted along two chains of six and five chimpanzees, respectively, such that the last chimpanzee in the chain used the same method as the original trained model. The fidelity of transmission within each chain is remarkable given that several individuals in the no-model control group were able to discover either method by individual exploration. A comparative study with human children revealed similar results. This study is the first to experimentally demonstrate the linear transmission of alternative foraging techniques by non-human primates. Our results show that chimpanzees have a capacity to sustain local traditions across multiple simulated generations. culture | diffusion chain | social learning | tradition

A study was conducted to determine how capuchins reacted to inequitable rewards in an unrestricted cooperative paradigm, and which reward they would receive for their participation. It was observed that equity of the reward distribution did not affect success or pulling behavior, but the behavior of the partner in an unequal situation - such as who received higher-value food - affected overall success rates, and the ability to equitably distribute rewards had profound implications for activities such as group hunts.

WALL STREET IS SOMETIMES COMPARED TO A DARWINIAN JUNGLE. Nice guys finish last, it is said, and only the strong survive. This is an adequate enough description, but not entirely [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2005.03.007 Byline: Amy S. Pollick, Harold Gouzoules, Frans B.M. de Waal Abstract: Brown capuchins give distinct calls upon encountering food. Based on studies on other species that point at divisibility of food and audience as critical variables, we predicted that capuchins would adjust their food calling for both the amount of food and the nature of their audience. We predicted that the food-associated call serves to attract conspecifics in certain conditions. Twelve female capuchins were tested in two food-quantity conditions (large and small) and four audience conditions with a control (higher-ranking female, lower-ranking female, high-ranking male, entire group and alone). All subjects called more for larger than smaller amounts and the highest-ranking females called less than others. Subjects called more in the presence of a group than for any other audience, and this applied most strikingly to high-ranking subjects. This result may be related to the presence of kin rather than group size. We also analysed the acoustic parameters of the calls, predicting that, under conditions where call production rose, those acoustic variables associated with heightened arousal would rise in value. However, call production and those acoustic features were not always correlated. These results suggest that food calls in this species do not solely reflect arousal caused by food and are influenced by multiple audience effects. Author Affiliation: Living Links, Yerkes National Primate Research Center and Psychology Department, Emory University Article History: Received 14 September 2004; Revised 9 October 2004; Accepted 4 March 2005 Article Note: (miscellaneous) MS. number: A10000R

It is widely assumed that monkeys see a stranger in the mirror, whereas apes and humans recognize themselves. In this study, we question the former assumption by using a detailed comparison of how monkeys respond to mirrors versus live individuals. Eight adult female and six adult male brown capuchin monkeys (Cebus apella) were exposed twice to three conditions: (i) a familiar same-sex partner, (ii) an unfamiliar same-sex partner, and (iii) a mirror. Females showed more eye contact and friendly behavior and fewer signs of anxiety in front of a mirror than they did when exposed to an unfamiliar partner. Males showed greater ambiguity, but they too reacted differently to mirrors and strangers. Discrimination between conditions was immediate, and blind coders were able to tell the difference between monkeys under the three conditions. Capuchins thus seem to recognize their reflection in the mirror as special, and they may not confuse it with an actual conspecific. Possibly, they reach a level of self-other distinction intermediate between seeing their mirror image as other and recognizing it as self. primate | self-awareness | empathy | development

The male-offspring biased visual kin recognition in chimpanzees (Pan troglodytes) reported by L. A. Parr and F. B. M. de Waal (1999) was replicated with human (Homo sapiens) participants and a principal components analysis (PCA) of pixel maps of the chimpanzee face photos. With the same original materials and methods, both humans and the PCA produced the same asymmetry in kin recognition as found with the chimpanzees. The PCA suggested that the asymmetry was a function of differences in the distribution of global characteristics associated with the framing of the faces in the son and daughter test sets. Eliminating potential framing biases, either by cropping the photos tightly to the faces or by rebalancing the recognition foils, eliminated the asymmetry but not human participants' ability to recognize chimpanzee kin.

Prescriptive social rules are enforced statistical regularities. The authors investigated whether juvenile chimpanzees (Pan troglodytes) recognize and use enforced statistical regularities to guide dyadic play behavior. They hypothesized (a) that proximity of adults, especially mothers of younger play partners, to play bouts will increase the play signaling of older partners and (b) that when juvenile--juvenile play bouts occur in proximity to adults, older partners will play at a lower intensity than when no adults are present. They found that older and younger partners increase their play signaling in the presence of the mothers of younger partners, particularly as the intensity of play bouts increases. In contrast to their hypothesis, older partners played more roughly when the mothers of younger partners were in proximity. These results suggest that juvenile chimpanzees increase play signaling to prevent termination of the play bouts by mothers of younger partners.

Social learning is assumed to underlie traditions, yet evidence indicating social learning in capuchin monkeys (Cebus apella), which exhibit traditions, is sparse. The authors tested capuchins for their ability to learn the value of novel tokens using a previously familiar token-exchange economy. Capuchins change their preferences in favor of a token worth a high-value food reward after watching a conspecific model exchange 2 differentially rewarded tokens, yet they fail to develop a similar preference after watching tokens paired with foods in the absence of a conspecific model. They also fail to learn that the value of familiar tokens has changed. Information about token value is available in all situations, but capuchins seem to pay more attention in a social situation involving novel tokens.

Mother-offspring (MO) relationship quality was investigated to determine its influence on the development of reconciliation--affiliation between opponents shortly after a fight--because it influences what distressed youngsters learn about calming down. Data were longitudinal and cross-sectional observational samples of 38 MO pairs of monkeys across 24 months. An MO relationship quality index (RQI) classified each pair as secure or insecure. Reconciliation emerged in infancy. Secure youngsters had an appeasing conciliatory style, and insecure youngsters had an agitated conciliatory style. Conclusions are that reconciliation develops from the attachment behavior system and MO RQI is related to the particular conciliatory style youngsters develop by affecting how aroused they are by conflict and the subsequent socializing they seek to calm down.

Two measures are reported of the nature or quality of a mother-offspring (MO) relationship during development using brown capuchin monkeys (Cebus apella) as models. One is a qualitative classification of MO relationships as secure, resistant, or avoidant attachments. The other is an empirical ratio of relative affiliation to agonism called the MO relationship quality, or MORQ, Index. The two methods tapped similar relationship features so relationships high or low of a median split of MORQ values were heuristically labeled secure (n = 22) or insecure (n = 16), respectively. A comparison revealed extensive behavioral differences between secure and insecure MO relationships and suggested MORQ provided an objective, continuous measure of attachment security.

There is disagreement in the literature about the exact nature of the phenomenon of empathy. There are emotional, cognitive, and conditioning views, applying in varying degrees across species. An adequate description of the ultimate and proximate mechanism can integrate these views. Proximately, the perception of an object's state activates the subject's corresponding representations, which in turn activate somatic and autonomic responses. This mechanism supports basic behaviors (e.g., alarm, social facilitation, vicariousness of emotions, mother-infant responsiveness, and the modeling of competitors and predators) that are crucial for the reproductive success of animals living in groups. The Perception-Action Model (PAM), together with an understanding of how representations change with experience, can explain the major empirical effects in the literature (similarity, familiarity, past experience, explicit teaching, and salience). It can also predict a variety of empathy disorders. The interaction between the PAM and prefrontal functioning can also explain different levels of empathy across species and age groups. This view can advance our evolutionary understanding of empathy beyond inclusive fitness and reciprocal altruism and can explain different levels of empathy across individuals, species, stages of development, and situations. Keywords: altruism; cognitive empathy; comparative; emotion; emotional contagion; empathy; evolution; human; perception-action; perspective taking

Capuchins have been found to cooperate when assigned a specific task, though the extent to which they do so may be affected by the type of task.

The attitudinal reciprocity in food sharing in brown capuchin monkeys was studied.

Although the construct of psychopathy has received considerable attention in humans, its relevance to other animals is largely unknown. We developed a measure of psychopathy for use in chimpanzees (Pan troglodytes), the Chimpanzee Psychopathy Measure (CPM), and asked 6 raters to complete this index on 34 chimpanzees. The CPM (a) demonstrated satisfactory interrater reliability and internal consistency; (b) exhibited marginally significant sex differences (males > females); (c) correlated positively with measures of extraversion, agreeableness, and observational ratings of agonism, sexual activity, daring behaviors, teasing, silent bluff displays, and temper tantrums, and negatively with observational ratings of generosity; and (d) demonstrated incremental validity above and beyond a measure of dominance. Although further validation of the CPM is needed, these findings suggest that the psychopathy construct may be relevant to chimpanzees.

Heart rate telemetry was explored as a means to access animal emotion during social interactions under naturalistic conditions. Heart rates of 2 middle-ranking adult females living in a large group of rhesus macaques (Macaca mulatta) were recorded along with their behavior. Heart rate changes during 2 types of interactions were investigated, while controlling for the effects of posture and activity. The risk of aggression associated with the approach of a dominant individual was expected to provoke anxiety in the approachee. This prediction was supported by the heart rate increase after such an approach. No increase was found when the approacher was a kin or a subordinate individual. The tension-reduction function of allogrooming was also supported. Heart rate decelerated faster during the receipt of grooming than in matched control periods.

Capuchin monkeys (Cebus apella) share food even if their partner is behind a mesh restraint. Pairs of adult capuchins were moved into a test chamber in which 1 monkey received cucumber pieces for 20 min and the other received apple slices during the following 20 min. Tolerant transfers of food occurred reciprocally among females: The rate of transfer from Female B to A in the second test phase varied with the rate from Female A to B in the first test phase. Several social mechanisms may explain this reciprocity. Whereas this study does not contradict cognitively complex explanations (e.g., mental record keeping of given and received food), the results are consistent with a rather simple explanation: that food sharing reflects a combination of affiliative tendency and high tolerance. The study suggests that sharing mechanisms may be different for adult male capuchins, with males sharing food more readily and less discriminatingly than females.

It is widely believed that overcrowding promotes increased aggression in animals, although some species, such as primates, have adopted formal mechanisms that help to alleviate social tension. A study of captive rhesus monkeys under diverse population densities is presented. It is shown that increasing density caused make monkeys to increase huddling and grooming behaviour, although aggression rates did not increase. It is concluded that different patterns of responses to overcrowding may depend upon the stability and strength of relationships.

Former opponents in corral-housed pigtail macaques, Macaca nemestrina, are selectively attracted to each other after a conflict, but well estabished and newly formed groups differ regarding reconciliation. Conflicts are reconclied more often between opponents with strong affiliation. The members of well-established groups reconcile more often than those of a newly formed one. The former group distributes its affiliative behavior less evenly, and focuses on relatively smaller number of partners. This produces more intense ties which increases the chances of reconciliation after conflict.

The spatial density model suggests that aggressive response increases with an increase in spatial density, and the coping model demonstrates improved social behavior in crowded conditions. These were assessed through a short-term crowding experiment involving an established group of 61 rhesus monkeys, Macaca mulatta, crowded into a familiar area, one-fifth the size of its normal enclosure. Evidence was apparent only in part for both models, and it was observed that the monkeys had a conflict avoidance strategy. An increase in huddling and a decrease in grooming were observed among kin. Avoidance and the bared-teeth display were significant among same-sexed adult partners.

Data from three studies on two captive groups of rhesus monkeys, Macaca mulatta, were used to test a hierarchical multiple regression model of adult social organization. The model followed the literature in assuming that matrilineal kinship affects rank distance, i.e. that the rank positions of related adults are generally closer to one another than the positions of unrelated adults. Rank distance, in turn, was assumed to affect affiliative behaviour, tolerance at feeding and drinking sites, and aggression. The model was tested with matrix permutation techniques that allow dyadic variation to be taken completely into account. The results confimed that rank distance correlates with a range of social behaviour independently of the effects of kinship. Several alternative functional explanations of the role of rank distance were compared; attraction among individuals with similar ranks appeared the most explanation. The study also addressed the general applicability of a previously reported 'class' division in one of the two groups. The division could not be replicated, and may have been a temporary structural phenomenon.