The effect of the prenatal endocrines on adult behavior patterns may be investigated using both experimental and clinical evidence. Guinea pigs treated with androgens during gestation give birth to females which show masculinized sex behavior when tested as adults. This behavior is manifest by an increased incidence of male-like mounting, decreased responsiveness to female hormones and refractoryness to being brought into heat. This situation is permanent. The adult female guinea pig, however, into which the androgens were injected or comparably treated nonpregnant females show no or only temporary masculinization.

Clinical date from individuals who had received androgens during development also give indications of psychosexual masculinization. Individuals without testicular differentiating substances seem to orient as females. As in the guinea pig, the mother carrying these modified fetuses seems unaffected.

The differential reactivity of the fetus and mother is believed dependent upon the relative sensitivity of the developing neural tissues in contrast to the reaction of the adult nervous tissues and the action of progestational substances found in the pregnant female.

The significance of these findings are considered in regard to the concomitant evolution of patterns of sexual differentiation and hormone dependent behavior traits.


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