Discussion of Robert J. Stoller's Article, Gender Identity and a Biological Force

As one looks back over the past decade of sex research, one sees a veritable breakthrough with respect to neurohumoral mechanisms in the hypothalamus. These mechanisms control pituitary functioning and, correlated with it, the behavioral functions appropriate to coition and procreation.1

Experimental work has, as of the present, been chiefly with mammals below the primates. In rats, it has proved possible to cause a male conceptus to be born with female external genitalia, provided the pregnant mother is treated, at the critical period of her pregnancy, with the antiandrogen, cyproterone.2 Such a feminized animal, when subjected to appropriate experimental hormonal regulation of estrus postnatally, will behave exclusively as a female

and will be treated as such by normal males in the colony.

The converse experiment is one of producing masculinized females by treating the pregnant mother with testosterone. This experiment has been carried out on primates, namely, rhesus monkeys. The daughter is born with a fully formed penis and empty scrotum, so that she is morphologically indistinguishable externally from a genetic male with cryptorchidism. During the prepubertal years, this animal behaves more like a normal male infant than a female, according to the criteria of amount of rough-and-tumble play, initiation of aggressive play, and initiation of male sexual posturing in play. Reports on adolescent sexual and mating behavior (with and without castration and experimental hormonal manipulation) are still awaited.

The sum total of all experiments, of which the foregoing are highlights, points to a general principle: In the embryonic differentiation of sex, includ