Abstract

On the basis of knowledge prior to 1988, Ashbrook pointed out that whereas most men are primarily dependent on the left cerebral hemisphere (“dominant hemisphere”) for verbally related functions, women show a greater hemispheric balance in this respect. For men, he argues, their possession of a “speaking” and a “non‐speaking hemisphere” results in a positive‐negative, bipolar way of thinking that may be characterized as dualistic and dialectically hierarchical. In contrast, the greater balance of hemispheric function in women appears to promote greater generalization and synthesis in their thinking.In this article I cite more recent neuroanatomical and brain imaging studies that provide further evidence of disparities in structure and function of the brains of men and women. As background for an attempt to explain these differences, I give a brief review of the triune evolution of the mammalian brain leading up to the human cerebrum. It is of major significance that the female has played a central role in mammalian evolution for more than 180 million years and that the evolutionary transition from reptilian therapsids to mammals is characterized by the develoment of (1) nursing conjoined with maternal care; (2) audiovocal communication or aiding mother‐offspring contact; and (3) play. In human beings, the infant‐carrying hypothesis suggests one means by which, over generations, certain parts of a woman's right hemisphere could undergo functional and eventual anatomical expansion. The mother‐infant communication of basic mammalian sounds with vowel and consonant components suggests a basis for the origination of speech.Finally, in an expansion of Ashbrook's original thesis, we arrive at the rovocative consideration that, unlike men, with their dialectical reasoning, women, with their more balanced brain, are provided with a trialectial ladder for climbing to achieve knowledge. In terms of quantum mechanics, the particle and wave would correspond to the substance and strength of the sides of the ladder, and the derived psychic information (which is neither matter nor energy) would compare to the rungs in between.