Motivational Systems in Rats and Monkeys:
Are They Homologous
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Although there was considerable resemblance in terms of apparent skeletomotor activity between the various acts and postures of the rat and monkey within each category, there was a consistent tendency for use of the mouth by the rat to be replaced or supplemented with use of the hands by the monkey. This occurred in offense, sex, self-grooming, and allogrooming.

The offense of the rat and monkey culminated in an attack that is remarkably similar in each species, a bite-and-kick attack directed at the back or opposite flank in the rat, and a bite-the-back attack directed at the back or back of the neck in the monkey. Preceding the attack there was often a full-attack posture in the rat, in which the rat lies across its opponent's back, and there was often rough restraint in the monkey, in which the monkey used the hands to hold down the opponent; the orientation of the two animals was similar in each. The rat, unlike the monkey, engaged in a series of "threat postures," including the offensive sideways posture, upright posture, and boxing. The monkey, unlike the rat, engaged in hitting or yanking the opponent with the hands.

The sexual behavior of the monkey in these studies was much more elaborate than that of the rat. Mounting behavior was similar, but in the monkey it was accompanied by a number of acts involving use of the hands for restraining the partner, masturbating, and autostimulation, and by a variety of facial expressions and vocalizations, as shown in Figure 2.

Self-grooming and scratching, it has been hypothesized, are responses to pheromone secretions associated with other behaviors, and they are more appropriately called "self-anointing" [Lehman and Adams, 1977] .New data reported here for the first time for the monkey support the hypothesis that was previously based only on data from the rat. Self-grooming occurred almost exclusively during those tests in which the animal had attacked, been attacked, or mounted the opponent. There was virtually no self-grooming, on the other hand, in either dominant or subordinate, if they had not engaged in offense, submission, or sex. In other words, one may hypothesize that those three motivational systems include among their motor patterns the secretion from skin glands, and that the self-anointing activity that we observed was a response to such secretions. Self-grooming was performed with the mouth in the rat. Although there was some occasional self-grooming with the mouth in the monkey, most self-grooming was done with the hands.

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