Hemisphere Deconnection and Unity in Conscious Awareness

Roger W. Sperry was the Hixon Professor of Psychobiology at the California Institute of Technology when he wrote this, having come to the brain from an earlier programme on nerve-fibre regeneration that produced the chemoaffinity hypothesis. The split-brain research summarised here was carried out on the commissurotomy patients operated on by Philip Vogel and Joseph Bogen, and it is the work for which Sperry shared the 1981 Nobel Prize in Physiology or Medicine.

The paper appeared in 1968 in American Psychologist, the American Psychological Association's general flagship journal, as a synthesising, interpretive statement rather than a single experiment — the place Sperry set out what the accumulating split-brain findings meant. Its claim is the one the topic still argues over: that severing the corpus callosum leaves each hemisphere with its own perception, learning, and memory, and that the right reading of this is two largely separate spheres of conscious awareness in a single head — two minds running in parallel.

This sits as a primary, foundational source for the science of consciousness, one step up from the individual experiments it draws together and reported by the man who directed the programme. It is the position Gazzaniga's 1967 popular account had already put before a general audience, and the one that Pinto and colleagues set out to overturn nearly fifty years later.

Sperry's stake was scientific, reputational, and partly philosophical. He was advancing a view of consciousness as an emergent, causally real property of brain organisation, against the behaviourism of his era, and the divided-consciousness reading of the split brain was the strongest evidence he had for treating conscious awareness as a thing a science could locate and divide. The interpretive leap from "the hemispheres process independently" to "there are two minds here" is the part later workers have contested.