When such subjects are given spatial synthetic tests, such as Koh's Block Test as used in the clinical studies above, the reverse is found. It is now the right hemisphere that is doing the work.
Further deductions can be made about what particular functions might be residual in the right hemisphere by considering 17 R. W. Sperry, Film presented at Princeton, February 1971.
18 David Galin and R. E. Ornstein, "Lateral specialization of cognitive mode: an EEG study," Psychofhysiology, 1972, 9: 412-418.
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The Mind of Man
what it is that the divine voices of the bicameral mind would have to do in particular situ-
ations. To sort out and synthesize experience
into directives to action, the gods would have to make certain kinds of recognitions.
Throughout the speeches of gods in ancient
literature, such recognitions are common. I do not mean recognitions of individuals in particular, but more generally of types of people, of classifications, as well as of individuals. One important judgment for a human being of any
century is the recognition of facial expression, particularly in regard to friendly or unfriendly intent. If a bicameral man saw an
unrecognized man coming toward him, it
would be of considerable survival value for
the god-side of his mentality to decide if the person was of friendly or unfriendly intent.
The adjoining figure is an experiment I de-
signed about ten years ago out of such a sup-
position. The two faces are mirror images of
each other. I have so far asked almost a thou-
sand people which face looks happier. Quite
consistently, about 80 percent of right-handed people chose the bottom face with the smile
These faces are mirror images of
going up on their left. They were thus judg-
each other. Stare at the nose of
ing the face with their right hemispheres, as-
each. Which face is happier?
suming, of course, that they were glancing at
the center of the face. This result can be made stronger by tachistoscopic presentation. With
the focal point in the center and flashed at one tenth of a second, the bottom face always looks happier to right-handed persons.
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An alternative hypothesis, of course, is that this tendency to judge facial expression by the left visual field is a carry-over of reading from left to right. And in our cultures it certainly enhances the effect. But that the hemispheric explanation is at the bottom of it is suggested by the results for left-handed people.
Fifty-five percent of left-handers chose the upper face as happier, suggesting that it was the left hemisphere making the judgment. And this cannot be understood on the reading-direction hypothesis. Also, in people who are completely left-lateralized, left-handed in every way, the likeliho6d of seeing the top face as happier seems to be much higher.
Recently we have made a similar finding, using photographs of an actor expressing sadness, happiness, disgust, and surprise.19
Our subjects, carefully screened for right-handedness, first stared at the fixation point in a tachistoscope, then were presented with one photograph flashed for a few milliseconds in the central position, and then with another either in the right or left visual field for the same duration. The subjects were asked to say whether the photographs were the same or different, and the time taken to make this decision was recorded. Most of the subjects were able to match facial expressions more correctly and in less time when the face was presented on the left and hence to the right hemisphere. In a control condition, scrambled pictures of the same facial expressions (which were really nonsense patterns) also could be matched more quickly and correctly when presented on the left, but not nearly as well as the facial expressions themselves.
Recent clinical evidence is in clear agreement. Failure to recognize faces, not just facial expressions, is much more frequently associated with damage to the right hemisphere than to the left. In clinical testing, the patient is asked to match the frontal view of a face with three-quarter views of the same face 19 These experiments were done by Jack Shannon. We are both grateful to Stevan Harnad for his criticism and suggestions.
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The Mind of Man
under different lighting conditions. Patients with lesions in the right hemisphere find this extremely difficult in comparison with normal subjects or patients who have lesions in the left hemisphere.20 Recognition of both faces and facial expression is therefore primarily a right hemisphere function.
And to tell friend from non-friend in novel situations was one of the functions of a god.
6. A New Look at the Brain
How, it may be argued, can such a system as this, a brain structured into what I have called a bicameral mind, this substrate of human civilization for thousands of years, involving such loci as we have mentioned in the model, how can its function change over so short a period of time, such that the admonitory voices are heard no more and that we have this new organization called consciousness? While the amount of genocide going on in the world during these changes was enough to allow some natural selection and evolution, I in no way wish to rest the case upon that. Such natural selection as did occur during these periods of the development of consciousness certainly assisted in its perpetuation, but could not be said to have evolved consciousness out of the bicameral mind in the sense that a seaPs flipper is evolved out of an ancestral paw.
A true understanding of the situation requires a different view of the brain from that which was usual a few decades ago. Its emphasis is the brain's plasticity, its redundant representation of psychological capacities within a specialized center or region, the multiple control of psychological capacities by several centers either paired bilaterally or as what Hughlings Jackson recognized as "representations" of a function lying at successively higher 20 H. Hecaen and R. Angelergues, "Agnosia for Faces (Prosopagnosia)," Archives of Neurology 7: 92-100, 1962; A. L. Benton and M. W. Allen, "Impairment in Facial Recognition in Patients with Cerebral Disease," Cortex, 1968, 4: 345-358.
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and phylogenetically younger levels of the nervous system.21
The organization of the mammalian brain in this fashion allows for those experimental phenomena brought together under the rubric of "recovery of function." Its emphasis gives a view of the brain much more plastic than usual, with a dramatic surplus of neurons such that, for example, 98 percent of the optic tracts can be cut in the cat, and brightness and pattern discrimination will remain.22 The brain teems with redundant centers, each of which may exert direct influence on a final common pathway, or modulate the operation of others, or both, their arrangements able to assume many forms and degrees of coupling between constituent centers.
All this redundant representation in multiple control gives us the notion of a much more changeable kind of brain than the earlier neurologists described. A particular behavior or group of behaviors engage a host of similar neurons in a given center and may call into play several different centers arranged in various patterns of inhibition and facilitation, depending upon their evolutionary status. And the tightness of the coupling between centers varies tremendously from one function to another.23 In other words, the amount of changeableness that the locus of cortical functions can undergo is different among different functions, but that such changeableness is a pronounced feature of the higher mammalian brain is becoming more and more apparent. The biological purpose or selective advantage of such redundant representation and multiple control and its resulting plasticity is twofold: it protects the organism against the effects of brain damage, and, perhaps more important, it provides an 21 Hughlings Jackson, "Evolution and Dissolution of the Nervous System," in Selected Writings of John Hughlings Jackson, J. Taylor, ed. (London: Staples Press, 1958), 2: 45-75.