ABSTRACT
Work on the differentiation of reproductive behaviors during the last 30 years has proceeded under the guidance of a well-formed prevailing theory. This theory states that androgenic hormones produced in the developing testis circulate through the blood, enter the brain, and as a result alter the structure and function of neurons important for maletypical and female-typical reproductive behaviors. This theory does not explain all of the data available. First, there are peripheral effects of hormones (for example, in the adult, effects on somatosensory inputs) (Kow and Pfaff, 1973; Kow, et al., 1979), which could include alterations not only of sensory services but also of motor capacities. Frank Beach emphasized that effects of this sort during development could constitute essential mechanisms in the development of reproductive behavior. Second, circulating androgens cannot explain (Arnold, 1995) all of the data available from certain songbirds.
