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The effects of hormones upon the social behavior of muroid rodents are considered on two levels: an analytic level that enumerates the neural sites of hormonal action; and a synthetic level that describes a few discrete reproductive states characterized by particular patterns of hormone secretion. On the analytic level, fifteen neural sites are identified where hormones affect social behavior. Motivational mechanisms of offense, exploration/marking, and male sexual behavior are facilitated by androgen. Motivational mechanisms of female sexual behavior, parental behavior, and exploration/marking are facilitated by estrogen. A consociate modulator, that switches the animal from defense to submission, is activated by corticosteroids and inhibited by prolactin. Three sets of olfactory filters are specifically facilitated by gonadal hormones. These filters are tuned to pheromones that are secreted by an opponent and that reflect the hormonal status of that opponent. Two types of motor patterning mechanisms are facilitated by androgen: male sexual reflexes organized in the spinal cord and certain mechanisms of scent-marking. At least one sensory system is directly facilitated by estrogen, the tactile receptive field that releases the motor pattern of lordosis. Finally, there are motor patterning mechanisns for the secretion of hormones that also can be the target for hormonal effects. Thus, the mechanism for the gonadotropic hormone release is facilitated by estrogen and androgen and suppressed by ACTH and progestin. Similarly, the secretion of prolactin releasing factors and prolactin is facilitated by ACTH and estrogen, and the secretion of corticotropin-re1easing factor and ACTH is suppressed by prolactin. There is a positive feedback relationship between certain motivational systems and their motor patterning mechanisms of hormonal secretion. On a synthetic level, this may be seen as producing a few discrete reproductive states. The reproductive readiness state is characterized by secretion of gonadal hormones. The reproductive postponement state is characterized by secretion of ACTH and corticosteroids and suppression of gonadal hormone production by means of a hypothesized "anti-gonad system." There is also a separate reproductive fulfillment state of the lactating female characterized by secretion of estrogen and prolactin. The possibility is also discussed that there is a reproductive state associated with emigration. In conclusion, the theory of reproductive states is used to elucidate the processes associated with domestication.
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