Recognizing Impossible Object Relations: Intuitions About Support in Chimpanzees (Pan troglodytes)

Using looking-time measures, the authors examined untrained chimpanzees’ (Pan troglodytes) ability to distinguish between adequate and inadequate support. In 3 experiments, the chimpanzees’ sensitivity to different support relations between 2 objects was assessed. In each experiment, the chimpanzees saw a possible and an impossible test event, presented as digital video clips. Looking times in the […]

Self-control and tool use in tufted capuchin monkeys (Cebus apella)

Self-control is defined as forgoing immediate gratification to obtain a greater reward. Tool use may relate to self-control because both behaviors may require foresight and deliberate control over one’s actions. The authors assessed 20 capuchin monkeys ( Cebus apella) for the ability to delay gratification in a tool task. Subjects were given rod-shaped food items […]

Play Signaling and the Perception of Social Rules by Juvenile Chimpanzees (Pan troglodytes)

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 […]

Ontogeny of social behavior in the megapode Australian brush-turkey (Alectura lathami)

Megapodes meet conspecifics at an unpredictable age, and it is unknown how their social behavior develops under such conditions. The authors induced encounters between 2-day-old socially naive hatchlings and up to 49-day-old chicks of the Australian brush-turkey (Alectura lathami) in a large outdoor aviary. All social behavior patterns found in older chicks were present in […]

Mother-infant relationships in baboons (Papio hamadryas): Predictors of differences and discontinuities in developmental pathways

This study uses hierarchical linear regression modeling to analyze sources of variation in the developmental pathways of mother-infant relationships and to search for behavioral discontinuities. The data come from 23 mother-infant dyads of baboons (Papio hamadryas), whose interactions were recorded longitudinally during the infants’ 1st year of life. The infant’s sex and the mother’s age […]

Deterioration of planning ability with age in Japanese monkeys (Macaca fuscata)

To investigate the ability of aged monkeys to plan and the effect of aging on this ability, performance in a food retrieval task was assessed in aged and younger Japanese monkeys (Macaca fuscata). In this task, the monkeys had to retrieve food items by selecting from a set of 9 holes, each of which contained […]

Socially Meaningful Vocal Plasticity in Adult Campbell’s Monkeys (Cercopithecus campbelli)

Campbell’s monkeys (Cercopithecus campbelli) frequently exchange vocalizations, the combined-harmonic calls, with individuals responding to one another’s calls. Previous work has shown that these calls can be grouped into several structural variants. Adult females differ in their variant repertoires, which may change during their adult life, particularly after changes in the group composition. Playback of females’ […]