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Capuchin monkeys, as well as several other primate species, show food-related tolerance in both captive and wild settings. Although researchers have revealed that past experience affects food-related tolerance, it is unclear if and how observing a partner's previous food consumption affects tolerance. This question is important to determine the proximate mechanism of food-related tolerance, which may lead to food sharing, co-feeding, or tolerated taking. We investigated whether perception of another's consumption of food affected the rate of tolerant food transfers among brown capuchin monkeys (Cebus apella). First, in the test condition, subjects observed their partner either eating (Eat-In View) or not eating food (No Eat-In View) through a window. In a control condition, the subjects could not observe the same partner behind an opaque screen, while the partner either ate (Eat-Out of View) or did not eat (No Eat-Out of View). After this, the subjects were provided with food to examine how well they tolerated their partner's access to it through the mesh. Tolerant food transfers were sharply reduced after the subjects had observed their partner eat, but not in the control condition or after they had observed the partner not eating. We consider two possible hypotheses for this behavior, one relates to the internal state of the subject after having seen their partner eat (i.e., increased competitiveness, aggression, or food motivation). The other hypothesis relates to how the subject understands the partner's motivational state after having witnessed food consumption, perhaps by grasping the partner's need. [ABSTRACT FROM AUTHOR]

We investigated whether capuchin monkeys (Cebus apella) would choose to observe a high- or low-status adult female from their group during experimental foraging tests. The subject was located in the center of a test chamber, with a low- and high-ranking demonstrator on either side of two partitions. A peephole allowed the subject to observe the models by looking through either respective partition. Each model was trained on one of the two different methods, lift or pull, for retrieving food from a foraging apparatus. There were 22 subjects and four models. During the 40-trial test sessions, subjects could choose which model they would watch in each trial. It was predicted that subjects would prefer observing the model with whom it was closer in rank, and therefore share greater affiliation with. Results showed that only half the subjects showed a preference and that preference was not linked to status. Relatedness played a larger role in determining if a subject showed a preference for a model, and a correlation was found for relatedness and observer preference. After the observer preference tests, subjects were presented with the foraging apparatus to determine if they displayed a preference for one of the two tasks. The majority of subjects (17/22) showed a preference for the pull method, suggesting that this method may have been more salient to the monkeys in this study. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Stable cooperation requires that each party’s pay-offs exceed those available through individual action. The present experimental study on brown capuchin monkeys (Cebus apella) investigated if decisions about cooperation are (a) guided by the amount of competition expected to follow the cooperation, and (b) made instantaneously or only after a period of familiarization. Pairs of adult monkeys were presented with a mutualistic cooperative task with variable opportunities for resource monopolization (clumped versus dispersed rewards), and partner relationships (kin versus nonkin). After pre-training, each pair of monkeys (N=11) was subjected to six tests, consisting of 15 2 min trials each, with rewards available to both parties. Clumped reward distribution had an immediate negative effect on cooperation: this effect was visible right from the start, and remained visible even if clumped trials alternated with dispersed trials. The drop in cooperation was far more dramatic for nonkin than kin, which was explained by the tendency of dominant nonkin to claim more than half of the rewards under the clumped condition. The immediacy of responses suggests a decision-making process based on predicted outcome of cooperation. Decisions about cooperation thus take into account both the opportunity for and the likelihood of subsequent competition over the spoils. [Copyright &y& Elsevier]

Studies the nature or quality of mother-offspring (MO) relationship during development using brown capuchin monkeys. Use of qualitative classification of MO relationship; Role of the empirical ratio of relative affiliation to agonism; Revelation of extensive behavioral differences between secure.

Focuses on the use of cooperative pulling tasks in assessing cooperative behavior in capuchin monkeys. Impact of visual contact elimination between partners on the success of cooperation; Observation of the monitoring behavior toward partner in cooperative and control tests; Factor affecting the level of coordination in monkeys.

Presents a study which suggests that sharing mechanisms may be different for adult male capuchins, with males sharing food more readily and less discriminating than females. Methodology used to conduct the study; Discussion based on the results of the study.

Spontaneous interactions over fruits and vegetables were observed in a captive group of Cebus apella. The group lacked fully grown males; 3 adult females dominated the remaining 11 individuals, most of which were adolescents and late juveniles. Apart from expressions of interest and unsuccessful attempts to claim food, interactions over food included two types of interindividual food transfer: forced claims (i.e., involuntary transfers) and peaceful sharing. These two categories represented 7.2% and 20.3% of 3,389 observed food interactions, respectively. Sharing of food was subdivided into four categories; the most frequent category was the collection of discarded food items from within reach of the possessor, and the least frequent was active giving of food items by the possessor. The voluntary nature of food transfers was further investigated in an experiment in which two monkeys were placed in adjacent cages with a wire-mesh partition between them. One subject received food; the other did not. Although this setup made it easy for possessors to prevent food transfers, sharing occurred in all 18 tests on different combinations of individuals. In 10 of the tests, possessors were observed to actively push food through the mesh partition to their partner. [ABSTRACT FROM AUTHOR]

During the evolution of cooperation it may have become critical for individuals to compare their own efforts and pay-offs with those of others. Negative reactions may occur when expectations are violated. One theory proposes that aversion to inequity can explain human cooperation within the bounds of the rational choice model, and may in fact be more inclusive than previous explanations. Although there exists substantial cultural variation in its particulars, this ‘sense of fairness’ is probably a human universal that has been shown to prevail in a wide variety of circumstances. However, we are not the only cooperative animals, hence inequity aversion may not be uniquely human. Many highly cooperative nonhuman species seem guided by a set of expectations about the outcome of cooperation and the division of resources. Here we demonstrate that a nonhuman primate, the brown capuchin monkey (Cebus apella), responds negatively to unequal reward distribution in exchanges with a human experimenter. Monkeys refused to participate if they witnessed a conspecific obtain a more attractive reward for equal effort, an effect amplified if the partner received such a reward without any effort at all. These reactions support an early evolutionary origin of inequity aversion. [ABSTRACT FROM AUTHOR]

We have shown that animals compare their own rewards with those of others, and accept or reject rewards according to their relative value. Our aim was not to demonstrate that capuchin monkeys make a human response to inequality, but rather to elucidate evolutionary precursors to inequity aversion. We use this term as in ref. 2 - “people resist inequitable outcomes; that is, they are willing to give up some material pay-off to move in the direction of more equitable outcomes” - and specifically focus on “disadvantageous inequity aversion”. The monkeys in our experiment could not change the reward division, and hence could not actively avoid inequality, but we wanted to determine whether they would at least recognize inequality if subjected to it. We found that the capuchins reacted negatively, refusing to complete the interaction. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]