A number of commentators agree that the evidence reviewed in
the target article supports a previously unrecognized role for ovarian
hormones in feminization of the brain. Others question this view,
suggesting that the traditional model of sexual differentiation
already accounts for ovarian influence. This position is supported by
various reinterpretations of the data presented (e.g., ovarian effects
are secondary to the presence/absence of androgen, ovarian effects
are smaller than testicular effects, ovarian effects are not
organizational). We discuss these issues, and reiterate our position
that evidence of neurobehavioral ovarian effects is incompatible with
the currently accepted model of sexual differentiation. Other points
regarding species generalizations, the direct versus indirect action
of estrogen, and nonhormonal mechanisms of sexual differentiation are
also discussed. Finally, we address the controversial issue of using
ratio scores in the assessment of the human corpus callosum (where
CC scores are divided by an index of brain size). Future applications
to human research are also discussed.