First Suckling: A Crucial Event for Mother–Young Attachment? An Experimental Study in Horses (Equus caballus)

This study investigates the consequences of interference during first suckling for subsequent mare-young attachment in horses (Equus caballus). Foals brought to their dams’ teats appeared, at later ages (1-3 months), to remain closer to their dams and to play less than control foals that had been allowed to suckle spontaneously. Higher levels of play and […]

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 […]

Do big-brained animals play more? Comparative analyses of play and relative brain size in mammals

It has been hypothesized that play is more likely to be present in larger brained species. We tested this hypothesis in mammals using independent contrasts, a method that controls for phylogenetic relatedness. Comparisons across 15 orders revealed that the prevalence and complexity of play was significantly correlated with brain size, with larger brained orders having […]

Depressive behavior in young monkeys subjected to vertical chamber confinement

Young rhesus monkeys were confined in vertical chambers for 6 wk., and their subsequent behavior over a 9-mo. period in both a home-cage and playroom situation was compared with that of like-aged monkeys housed individually or in pairs. In comparison to both control groups, chambered monkeys exhibited excessive amounts of self-clasp and huddle, abnormally low […]