To whom the play signal is directed: A study of headshaking in black-handed spider monkeys (Ateles geoffroyi).

Abstract

Spider monkeys shake their heads so as to facilitate amicable social contact. This occurs frequently during vigorous play fighting, and so is common during the juvenile period. Occasionally, juvenile spider monkeys use headshakes during nonsocial locomotor play. In this study, head shaking in early infancy and in adulthood was studied in a captive troop of spider monkeys, with a total of 8 infants studied from shortly after birth to just before weaning. Three hypotheses to account for these nonsocial headshakes were tested. The play as the experience of the unexpected hypothesis was found wanting because nonsocial headshakes were most common in early infancy, before the onset of the juvenile peak in play. The immature misdirection of signals hypothesis was also found wanting because the headshakes were correctly directed at other monkeys, but not at inanimate objects that were grabbed and mouthed. Both also failed to predict the occurrence of the observed nonsocial headshakes in adults. The hypothesis best supported by the data is that, under some situations, headshakes are self-directed to promote action when confronting contexts of uncertainty.

A novel escapable social interaction test reveals that social behavior and mPFC activation during an escapable social encounter are altered by post-weaning social isolation and are dependent on the aggressiveness of the stimulus rat

“…Playful attacks typically decline throughout puberty [42,43], suggesting that ISO rats may remain in an immature stage of social development. Play-like social interactions that vary too far from the expected behaviors are no longer considered playful [44] and may instead be interpreted as aggressive, thus provoking aggression from the experimental rats. Regardless of whether the interactions are agonistic or simply age-inappropriate, rats engaging in high levels of these behaviors may model social ineptness in adolescence.…”

Brain regional differences in social encounter-induced Fos expression in male and female rats after post-weaning social isolation

“…Playful attacks decline throughout puberty (Panksepp, 1981), suggesting that PSI rats may be “stuck” in an immature stage of social development, and this may be unexpected by the stimulus rat. Pellis and Pellis (2011) have suggested that play-like social interactions that vary too far from the expected behaviors are no longer considered playful, so that conspecifics avoid interactions with the individuals engaging in these behaviors.…”

Ontogenetic Trajectories of Chimpanzee Social Play: Similarities with Humans

“…Recently, Pellis and Pellis [77] demonstrated that the role of play signals in self-regulating emotional state is also present in spider monkeys. Yet, there are some greater cognitive overlap and developmental similarities between Pan and Homo than between either and other primate species.…”