MULTIPLE DIFFERENCES IN THE PLAY FIGHTING OF MALE AND FEMALE RATS - IMPLICATIONS FOR THE CAUSES AND FUNCTIONS OF PLAY

Play fighting is the most commonly occurring form of social play in ju venile mammals. Typically, males engage in more play fighting than fem ales, and this difference has been shown to depend on the action of an drogens perinatally. It is generally believed that the differences in play fighting between the sexes are quantitative and do not involve qu alitative differences in the behavior performed. We show that this is an incorrect characterization of sex differences in play fighting. For example, in laboratory rats, there are at least five different mechan isms that contribute to the observed sex differences in play fighting. These mechanisms involve (I) the motivation to initiate play, (II) th e sensory capacity to detect and respond to a play partner, (III) the organization of the motor patterns used to interact with a partner, (I V) age-related changes at puberty in initiating play and in responding to playful contact, and (V) dominance-related changes in adulthood in the pattern of playful interaction. Sex differences in the play fight ing of rats are due to an interaction of all of these mechanisms, some of which are sex-typical, not play-typical, and involve both quantita tive and qualitative differences. This is clearly different from the p revailing view that play fighting is a unitary behavior which is mascu linized perinatally. Indeed, even though all five mechanisms are andro genized perinatally, the sensorimotor differences also involve defemin ization (i.e. reduction of female-typical qualities). This expanded vi ew of the mechanisms contributing to the sex differences in play fight ing has implications for both the analysis of the neural systems invol ved, and for the functional significance of this activity in childhood and adulthood. Copyright (C) 1996 Elsevier Science Ltd.