Mental Duality in the Anatomically Intact Cerebrum

Joseph E. Bogen, Presented in part as the outgoing Presidential Address to the Los Angeles Society of Neurology and Psychiatry, January 19, 1983.
Portions of this essay have appeared in the following: D.F. Benson and E. Zaidel, eds. The Dual Brain (Guilford, NY, 1985); F. Lepore, M. Ptito, H.H. Jasper, eds. Two Hemispheres, One Brain? (Alan Liss, NY, 1986); and C. Trevarthen, ed. Brain Circuits and Functions of Mind (Cambridge: Cambridge University Press, 1990).

Excerpt: This paper is a followup to my articles called “The Other Side of the Brain” which were published in the Bulletin of the Los Angeles Neurological Society in 1969 (24). Those articles presented ideas some of which may now seem fairly orthodox. But in those days they were not, and I think that for Dr. Richard Walter, then editor of the Bulletin to publish them was a tribute to his wry sense of humor, as well as his historical perspective.

I shall now present evidence accumulated since 1969 that the onebrain view is inadequate to describe not only the “split-brain” but also the anatomically intact encephalon. I shall consider in some detail the possibility of retaining both the single brain and double brain views, as an example of complementarity, a philosophical concept adopted by some quantum physicists. Hence, a few philosophical ideas implicit in the remainder of the paper should be mentioned.

Does an individual having two cerebral hemispheres have, in some important sense, two brains rather than only one? This “important sense” deserves to be made more explicit at the outset. It includes, I believe, the following: that whatever may be for neurologists the meaning of the psychological term “mind,” the number of brains in an individual is the same as the number of minds. If this equivalence of numerosity were not agreed upon, we might well spend the rest of our time arguing that question as well as others, such as: What meanings are possible for the word “mind”? Without demeaning such perennial questions, I will take it for granted, at least for this paper, that what we can learn about mind also tells us about brain and vice versa. In other words, the mentalistic and physiologic are two different descriptions of the same underlying reality.

When discussing the duality versus singularity of brain, or in shifting back and forth between mentalistic and physiologic vocabularies, we are not concerned with a quite different issue, one which is often couched in misleadingly similar terms. That is, we are not here concerned with the metaphysical issue of dualism vs monism, whether the monism be materialistic or idealistic. Whether one professes (as have so many Eastern philosophers and some contemporary quantum physicists) (68) that mind begets brain, or whether one supposes [along with Sir Charles Sherrington, (9)] that mind coexists with and interacts with brain, or whether one supposes (as I believe) that mind is generated by brain, need not concern us here. Our metaphysical views neither entail nor are they entailed by our views on the question at hand. This is because one could easily be on either side of the dualism /monism issue irrespective of one’s position on the question of duality or singularity of mind.

How is it that this question (duality versus singularity of brain) has come so forcefully to our attention in the past few years?

The view that the brain should be considered not as a single organ but rather as a pair of organs, in much the same sense that each of us has a pair of kidneys or a pair of lungs, is at least as old as the writings of Hippocrates. In his words, “… the human brain, as in the case of all other animals, is double” (10). This view was urged with utmost conviction by Arthur Ladbroke Wigan, an English physician who published his book, The Duality of the Mind, in 1844. Among the many other similar sentiments in this book, he claimed that, “the mind is essentially dual like the organs by which it is exercised.” He believed himself able to prove, “that a separate and distinct process of thinking or ratiocination may be carried on in each cerebrum simultaneously” (11). Today we call this the concept of cerebral duality or hemispheric independence; it is important to understand that this proposition is not dependent upon the existence of hemispheric specialization; it is true of cats, monkeys, etc., as well as humans. …