“inserted in slot machines” to a twenty-five-cent piece.12
Moreover, the right hemisphere in these patients can respond emotionally without the left talking hemisphere knowing what it 12 M. S. Gazzaniga and R. W. Sperry, “Language after section of the cerebral commissures,” Brain, 1967, 90.131-148.
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is all about. If among a series of neutral geometric figures being flashed to the right and left visual fields at random, which means respectively into the left and right hemispheres, and then a picture of a nude girl by surprise is flashed on the left side going into the right hemisphere, the patient (really the patient's left hemisphere) says that it saw nothing or just a flash of light. But the grinning, blushing, and giggling during the next minute contradicts what the speech hemisphere has just said. Asked what all the grinning is about, the left or speech hemisphere replies that it has no idea.13 These facial expressions and blushings, incidentally, are not confined to one side of the face, being mediated through the deep interconnections of the brainstem. The expression of affect is not a cortical matter.
Similarly with other sensory modalities. Odors presented to the right nostril and so to the right hemisphere (olfactory fibers do not cross) in these patients cannot be named by the talking hemisphere, though the latter can say very well whether the smell is pleasant or unpleasant. The patient may even grunt, make aversive reactions, or exclaim "Phew!" to a stench, but cannot say verbally whether it is garlic, cheese, or decayed matter.14 The same odors presented to the left nostril can be named and described perfectly well. What this means is that the emotion of disgust gets across to the speaking hemisphere through the intact limbic system and brainstem, while the more specific information processed by the cortex does not.
Indeed, there is some indication that it is the right hemisphere that commonly triggers the emotional reactions of displeasure from the limbic system and brainstem. In test situations, where the speechless right hemisphere is made to know the correct answer, and then hears the left dominant hemisphere making 13 R. W. Sperry, "Hemisphere Deconnection."
14 H. W. Gordon and R. W. Sperry, "Olfaction following surgical disconnection of the hemisphere in man," Proceedings of the Psychonomic Society, 1968.
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obvious verbal mistakes, the patient may frown, wince, or shake his head. It is not simply a way of speaking to say that the right hemisphere is annoyed at the erroneous vocal responses of the other. And so perhaps the annoyance of Pallas Athene when she grasped Achilles by his yellow hair and twisted him away from murdering his king (Iliad, 1 .-197). Or the annoyance of Yahweh with the iniquities of his people.
Of course there is a difference. Bicameral man had all his commissures intact. But I shall suggest later that it is possible for the brain to be so reorganized by environmental changes that the inferences of my comparison here are not entirely foolish. At any rate, the studies of these commissurotomy patients demonstrate conclusively that the two hemispheres can function so as to seem like two independent persons, which in the bicameral period were, I suggest, the individual and his god.
4. That Hemispheric Differences in Cognitive Function Echo the Differences of God and Man
If this brain model of the bicameral mind is correct, it would predict decided differences in cognitive function between the two hemispheres. Specifically, we would expect that these functions necessary for the man-side would be in the left or dominant hemisphere, and those functions necessary to the gods would be more emphasized in the right hemisphere. Moreover, there is no reason not to think that the residuals of these different functions at least are present in the brain organization of contemporary man.
The function of the gods was chiefly the guiding and planning of action in novel situations. The gods size up problems and organize action according to an ongoing pattern or purpose, resulting in intricate bicameral civilizations, fitting all the disparate parts together, planting times, harvest times, the sorting out of commodities, all the vast putting together of things in a grand
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design, and the giving of the directions to the neurological man in his verbal analytical sanctuary in the left hemisphere. We might thus predict that one residual function of the right hemisphere today would be an organizational one, that of sorting out the experiences of a civilization and fitting them together into a pattern that could 'tell' the individual what to do. Perusal of various speeches of gods in the Iliad, the Old Testament, or other ancient literatures is in agreement with this. Different events, past and future, are sorted out, categorized, synthesized into a new picture, often with that ultimate synthesis of metaphor. And these functions should, therefore, characterize the right hemisphere.
Clinical observations are consistent with this hypothesis. From the commissurotomized patients of a few pages past, we know that the right hemisphere with its left hand is excellent at sorting out and categorizing shapes, sizes, and textures. From brain-damaged patients, we know that damage to the right hemisphere interferes with spatial relations and with gestalt, synthetic tasks.15 Mazes are problems in which various elements of a spatial pattern must be organized in learning. Patients in whom the right temporal lobe has been removed find learning the pathways of visual and tactile mazes almost impossible, while patients with lesions of equal extent on the left temporal lobe have little difficulty.16
Another task involving the organization of parts into a spatial pattern is Koh's Block Test, commonly used in many intelligence tests. The subject is shown a simple geometric pattern, and asked to duplicate it with blocks that have its elements painted on them. Most of us can do it easily. But patients with brain lesions 15 H. Hecaen, "Clinical Symptomatology in Right and Left Hemispheric Lesions,"
in Inter hemispheric Relations and Cerebral Dominance, V. B. Mountcastle, ed.
(Baltimore: Johns Hopkins Press, 1962).
16 Brenda Milner, "Visually guided maze learning in man: effects of bilateral, frontal, and unilateral cerebral lesions," Neuropsychologia, 1965, 3: 317-338.
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in the right hemisphere find this extremely difficult, so much so that the test is used to diagnose right hemisphere damage. In the commissurotomy patients referred to earlier, the right hand often cannot succeed at all in putting the design together with the blocks. The left hand, in a sense the hand of the gods, has no problem whatever. In some of the commissurotomy patients, the left hand had even to be held back by the observer as it tried to help the right hand in its fumbling attempts at this simple task.17
The inference has thus been drawn from these and other studies that the right hemisphere is more involved in synthetic and spatial-constructive tasks while the left hemisphere is more analytic and verbal. The right hemisphere, perhaps like the gods, sees parts as having a meaning only within a context; it looks at wholes. While the left or dominant hemisphere, like the man side of the bicameral mind, looks at parts themselves.
These clinical results have been confirmed in normal people in what promises to be the first of many future studies.18 E E G
electrodes were placed over the temporal and parietal lobes on both sides of normal subjects who were then given various tests.
When asked to write various kinds of letters involving verbal and analytic abilities, the E E G records show low-voltage fast waves over the left hemisphere, denoting that the left hemisphere is doing the work, while slow alpha waves (seen on both hemispheres in a resting subject with the eyes closed) are seen over the right hemisphere, indicating that it is not doing the work.