“Accidents or strokes in the temporal or parietal lobes of the left hemisphere of the neocortex characteristically result in impairment of the ability to read, write, speak and do arithmetic. Comparable lesions in the right hemisphere lead to impairment of three-dimensional vision, pattern recognition, musical ability and holistic reasoning. Facial recognition resides preferentially in the right hemisphere, and those who “never forget a face” are performing pattern recognition on the right side. Injuries to the right parietal lobe, in fact, sometimes results in the inability of a patient to recognize his own face in a mirror or photograph. Such observations strongly suggest that those functions we describe as “rational” live mainly in the left hemisphere, and those we consider “intuitive,” mainly in the right.”
“Sperry and his collaborators have performed an elegant series of experiments in which separate stimuli are presented to the left and right hemispheres of split-brain patients. In a typical experiment, the word hat-band is flashed on a screen—but hat is in the left visual field and band in the right visual field. The patient reports that he saw the word band, and it is clear that, at least in terms of his ability to communicate verbally, he has no idea that the right hemisphere received a visual impression of the word hat. When asked what kind of band it was, the patient might guess: outlaw band, rubber band, jazz band. But when, in comparable experiments, the patient is asked to write what he saw, but with his left hand inside a box, he scrawls the word hat. He knows from the motion of his hand that he has written something, but because he cannot see it, there is no way for the information to arrive in the left hemisphere which controls verbal ability. Bewilderingly, he can write, but cannot utter, the answer.”
“The left hemisphere processes information sequentially; the right hemisphere simultaneously, accessing several inputs at once. The left hemisphere works in series; the right in parallel. The left hemisphere is something like a digital computer; the right like an analog computer. Sperry suggested that the separation of function in the two hemispheres is the consequence of a “basic incompatibility.” Perhaps we are today able to sense directly the operations of the right hemisphere mainly when the left hemisphere has “set”—that is, in dreams.”
“There are occasional but reliably reported instances of difficult intellectual problems solved during sleep. Perhaps the most famous is the dream of the German chemist Friedrich Kekulé von Stradonitz. In 1865 the most pressing and puzzling problem in organic structural chemistry was the nature of the benzene molecule. The structure of several simple organic molecules had been deduced from their properties, and all were linear, the constituent atoms being attached to each other in a straight line. According to his own account, Kekulé was dozing on a horse-drawn tram when he had a kind of dream of dancing atoms in linear arrangements. Abruptly the tail of a chain of atoms attached itself to the head and formed a slowly rotating ring. On awakening and recalling this dream fragment, Kekulé realized instantly that the solution to the benzene problem was a hexagonal ring of carbon atoms rather than a straight chain. Observe, however, that this is quintessentially a pattern-recognition exercise and not an analytic activity. It is typical of almost all of the famous creative acts accomplished in the dream state: they are right-hemisphere and not left-hemisphere activities.”
“Almost without exception all human languages have built into them a polarity, a veer to the right. “Right” is associated with legality, correct behavior, high moral principles, firmness, and masculinity; “left,” with weakness, cowardice, diffuseness of purpose, evil, and femininity. In English, for example, we have “rectitude,” “rectify,” “righteous,” “right-hand man,” “dexterity,” “adroit” (from the French “à droite”), “rights,” as in “the rights of man,” and the phrase “in his right mind.” Even “ambidextrous” means, ultimately, two right hands.
On the other side (literally), we have “sinister” (almost exactly the Latin word for “left”), “gauche” (precisely the French word for “left”), “gawky,” “gawk,” and “left-handed compliment.” The Russian “nalevo” for “left” also means “surreptitious.” The Italian “mancino” for “left” signifies “deceitful.” There is no “Bill of Lefts.”
“There is no way to tell whether the patterns extracted by the right hemisphere are real or imagined without subjecting them to left-hemisphere scrutiny. On the other hand, mere critical thinking, without creative and intuitive insights, without the search for new patterns, is sterile and doomed. To solve complex problems in changing circumstances requires the activity of both cerebral hemispheres: the path to the future lies through the corpus callosum.”
“In the seventeenth century there were two quite distinct ways of describing the connection between mathematical quantities: you could write an algebraic equation or you could draw a curve. René Descartes showed the formal identity of these two views of the mathematical world when he invented analytical geometry, through which algebraic equations can be graphed. (Descartes, incidentally, was also an anatomist concerned about the localization of function in the brain.) Analytical geometry is now a tenth-grade commonplace, but it was a brilliant discovery for the seventeenth century. However, an algebraic equation is an archetypical left-hemisphere construction, while a regular geometrical curve, the pattern in an array of related points, is a characteristic right-hemisphere production. In a certain sense, analytical geometry is the corpus callosum of mathematics. Today a range of doctrines find themselves either in conflict or without mutual interaction. In some important instances, they are left-hemisphere versus right-hemisphere views. The Cartesian connection of apparently unrelated or antithetical doctrines is sorely needed once again.”