The underlying assumption in popular and scientific publications on sex differences in the brain is that human brains can take one of two forms “male” or “female,” and that the differences between these two forms underlie differences between men and women in personality, cognition, emotion, and behavior. Documented sex differences in brain structure are typically taken to support this dimorphic view of the brain. However, neuroanatomical data reveal that sex interacts with other factors in utero and throughout life to determine the structure of the brain
, and that because these interactions are complex, the result is a multi-morphic, rather than a dimorphic, brain
. More specifically, here I argue that human brains are composed of an ever-changing heterogeneous mosaic of “male” and “female” brain characteristics (rather than being all “male” or all “female”) that cannot be aligned on a continuum between a “male brain” and a “female brain
.” I further suggest that sex differences in the direction of change in the brain mosaic following specific environmental events lead to sex differences in neuropsychiatric disorders.
A Concluding Remark
Evidence that the structure of the brain is responsive to pre- and post-natal manipulations and that these may affect sex differences in brain structure is not new (e.g., Juraska, 1991). It has also been noted that sexual differentiation may progress independently in different brain tissues thus enabling genetically and environmentally induced variation in sexual differentiation of different tissues within a single brain (e.g., Simerly, 2002; Hines, 2004; Arnold, 2009; McCarthy et al. 2009; Sakuma 2009). Yet these effects have typically been treated as increasing variability in brain structure and thus obscuring sex differences (e.g., Juraska 1991). I would like to stress that I claim that there is no “true dimorphism” that is obscured by genetically and environmentally induced variability. There are no “true” “male” and “female” brains out there to discover. The true nature of the brain is that its form is highly variable. This variability is created by the interaction of genes (on sex chromosomes and on autosomal chromosomes), hormones (gonadal and others) and environment, in utero and throughout life.
I find the claims of Daphna Joel highly correlated to the concept of yin-yang. The relative magnitude of the two forces in us and the subsequent balance between them determine who we are. Every one of us is unique and special but we can't deny that we are both masculine and feminine to the core.
Furthermore, two paragraphs of The Manipulated Man came to mind after reading the above publication:
At birth, men and women have the same intellectual potential; there is no primary
difference in intelligence between the sexes. It is also a fact that potential left to
stagnate will atrophy. Women do not use their mental capacity: they deliberately let it
disintegrate. After a few years of sporadic training, they revert to a state of
irreversible mental torpor.
Why do women not make use of their intellectual potential? For the simple reason
that they do not need to. It is not essential for their survival. Theoretically it is
possible for a beautiful woman to have less intelligence than a chimpanzee and still
be considered an acceptable member of society.