Story of Psychology - Morton Hunt [66]
Still later, two German physiologists, Gustav Fritsch and Eduard Hitzig, identified a special region of the cortex—a strip running up and over the brain from left midbrain to right midbrain—as the site of motor control. Other investigators located areas responsible for vision, touch, and hearing. Toward the end of the century Flourens’s belief that there was no localization of function began to seem quite wrong and Gall’s view quite right, although totally wrong in detail. But in the twentieth century, further research would show that both theories are correct. Many functions reside in specific areas of the human brain, but learning, intelligence, memory, reasoning, decision making, and other high-level mental processes take place throughout the frontal lobes.
Flourens himself once summed up the approach of every science to truth by means of such to-and-fro swings of theory: “La science n’est pas,” he said; “elle devient” (Science is not; it becomes).12
What psychology has become is due, in part, to Gall. His discoveries of brain structure have stood the test of time, his absurd theory of phrenology led to the experimental study of the localization of brain functions, and his emphasis on the cortex as the seat of intelligence moved psychology farther than ever from metaphysics and closer than ever to empirical science. He deserves better than to be remembered only for his venture into pseudo-science.
The Mechanists
The mapping of the brain was part of a new and larger movement that sought to explain psychological phenomena in physiological terms. Democritus and a few others, to be sure, had hazarded guesses as to the physical events underlying perception and thought, but throughout the centuries most philosopher-psychologists had theorized about mental events in terms of invisible high-level processes such as association, reason, and will. Knowing next to nothing about the physiology of the nervous system and brain, they ignored the question of whether these processes were made up of physical events.
But, as we have seen, with the emergence of physics and chemistry in the seventeenth century a few daring protopsychologists began suggesting mechanical explanations of mental processes. Lacking actual observational data, they speculated about “animal spirits” coursing through hollow nerves (Descartes), atoms streaming through the nerves (Hobbes), nerves aquiver with “vibratiuncles” (Hartley), and a French philosopher, Julien de La Mettrie, even wrote a book in 1748 titled L’Homme Machine (Man a Machine).
During the eighteenth century and the early part of the nineteenth, however, physiologists made a number of discoveries about the nervous system that led them to begin explaining lower-level psychological processes, such as perception, reflexes, and voluntary movements, in terms of physical and chemical events that could actually be observed in the nerves. Among the discoveries that made possible this new physiological psychology:13
—Around 1730, Stephen Hales, an English botanist and chemist, decapitated a frog, then pinched it; its legs drew up. He destroyed its spinal cord and pinched it again; this time the legs did not move. Hales thereby established the difference between reflex and voluntary actions, and located the source of the reflex in the spinal cord, not the brain.
—In 1791 the Italian physiologist Luigi Galvani hung a frog’s leg, with part of the spinal cord attached, from a brass hook; when he produced an electrical discharge from a nearby Leyden jar, the leg kicked. Galvani concluded that “animal electricity,” generated in the muscles and brain, flows through nerves and is responsible for movement.
—Until the early nineteenth century, physiologists supposed that the nervous system was like a network of continuous wires. But in the early years of that century, when it was established that plant tissues