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Brosnan, S. F., & de Waal, F. B. M. (2004). Socially learned preferences for differentially rewarded tokens in the brown capuchin monkey (Cebus apella). J Comp Psychol, 118(2), 133–139.
Abstract: 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.
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Klein, E. D., & Zentall, T. R. (2003). Imitation and affordance learning by pigeons (Columba livia). J Comp Psychol, 117(4), 414–419.
Abstract: The bidirectional control procedure was used to determine whether pigeons (Columba livia) would imitate a demonstrator that pushed a sliding screen for food. One group of observers saw a trained demonstrator push a sliding screen door with its beak (imitation group), whereas 2 other groups watched the screen move independently (possibly learning how the environment works) with a conspecific either present (affordance learning with social facilitation) or absent (affordance learning alone). A 4th group could not see the screen being pushed (sound and odor control). Imitation was evidenced by the finding that pigeons that saw a demonstrator push the screen made a higher proportion of matching screen pushes than observers in 2 appropriate control conditions. Further, observers that watched a screen move without a demonstrator present made a significantly higher proportion of matching screen pushes than would be expected by chance. Thus, these pigeons were capable of affordance learning.
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Stoinski, T. S., & Whiten, A. (2003). Social learning by orangutans (Pongo abelii and Pongo pygmaeus) in a simulated food-processing task. J Comp Psychol, 117(3), 272–282.
Abstract: Increasing evidence for behavioral differences between populations of primates has created a resurgence of interest in examining mechanisms of information transfer between individuals. The authors examined the social transmission of information in 15 captive orangutans (Pongo abelii and Pongo pygmaeus) using a simulated food-processing task. Experimental subjects were shown 1 of 2 methods for removing a suite of defenses on an “artificial fruit.” Control subjects were given no prior exposure before interacting with the fruit. Observing a model provided a functional advantage in the task, as significantly more experimental than control subjects opened the fruit. Within the experimental groups, the authors found a trend toward differences in the actual behaviors used to remove 1 of the defenses. Results support observations from the wild implying horizontal transfer of information in orangutans and show that a number of social learning processes are likely to be involved in the transfer of knowledge in this species.
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Weaver, A., & de Waal, F. B. M. (2003). The mother-offspring relationship as a template in social development: reconciliation in captive brown capuchins (Cebus apella). J Comp Psychol, 117(1), 101–110.
Abstract: 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 influenceswhat 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.
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Weaver, A., & de Waal, F. B. M. (2002). An index of relationship quality based on attachment theory. J Comp Psychol, 116(1), 93–106.
Abstract: 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.
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Parr, L. A., Winslow, J. T., Hopkins, W. D., & de Waal, F. B. (2000). Recognizing facial cues: individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). J Comp Psychol, 114(1), 47–60.
Abstract: Faces are one of the most salient classes of stimuli involved in social communication. Three experiments compared face-recognition abilities in chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). In the face-matching task, the chimpanzees matched identical photographs of conspecifics' faces on Trial 1, and the rhesus monkeys did the same after 4 generalization trials. In the individual-recognition task, the chimpanzees matched 2 different photographs of the same individual after 2 trials, and the rhesus monkeys generalized in fewer than 6 trials. The feature-masking task showed that the eyes were the most important cue for individual recognition. Thus, chimpanzees and rhesus monkeys are able to use facial cues to discriminate unfamiliar conspecifics. Although the rhesus monkeys required many trials to learn the tasks, this is not evidence that faces are not as important social stimuli for them as for the chimpanzees.
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Lilienfeld, S. O., Gershon, J., Duke, M., Marino, L., & de Waal, F. B. (1999). A preliminary investigation of the construct of psychopathic personality (psychopathy) in chimpanzees (Pan troglodytes). J Comp Psychol, 113(4), 365–375.
Abstract: 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.
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Aureli, F., Preston, S. D., & de Waal, F. B. (1999). Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): a pilot study. J Comp Psychol, 113(1), 59–65.
Abstract: 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.
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de Waal, F. B. (1997). Food transfers through mesh in brown capuchins. J Comp Psychol, 111(4), 370–378.
Abstract: 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.
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de Waal, F. B. (1996). Macaque social culture: development and perpetuation of affiliative networks. J Comp Psychol, 110(2), 147–154.
Abstract: Maternal affiliative relations may be transmitted to offspring, similar to the way in which maternal rank determines offspring rank. The development of 23 captive female rhesus monkeys (Macaca mulatta) was followed from the day of birth until adulthood. A multivariate analysis compared relations among age peers with affiliative relations, kinship, and rank distance among mothers. Maternal relations were an excellent predictor of affiliative relations among daughters, explaining up to 64% of the variance. Much of this predictability was due to the effect of kinship. However, after this variable had been controlled, significant predictability persisted. For relations of female subjects with male peers, on the other hand, maternal relations had no significant predictive value beyond the effect of kinship. One possible explanation of these results is that young rhesus females copy maternal social preferences through a process of cultural learning.
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