by Morton Hunt
Gall described his findings in a series of massive volumes published between 1810 and 1819. Spurzheim co-authored the first two but then went his own way; dynamic and charming, he became a highly successful lecturer and popularizer of phrenology in Europe and in the United States. Through Gall’s books and self-promotion and Spurzheim’s public appearances, phrenology became immensely popular and remained so for nearly a century. At one time, in Great Britain alone there were twenty-nine phrenological societies and several phrenological journals. In New York City, phrenological “parlors” sprang up on Broadway, and itinerant phrenologists gave readings all over the United States. In its heyday, phrenology was the vogue among ordinary folk, who sought in it answers to life’s dilemmas. More surprisingly, many distinguished people and serious intellectuals believed in it: Hegel, Bismarck, Marx, Balzac, the Brontës, George Eliot, Walt Whitman, and others.
But from the first it met with powerful scientific opposition, and for good reason. For one thing, Gall collected and presented cases that fit his theory when he should have measured random samples of people and shown that bumps were correlated with hyperdevelopment of the traits in question and the absence of bumps with normal or less than normal development of those traits. For another, when an individual with a cranial prominence failed to have the predicted trait, Gall explained it in terms of the “balancing action” of other brain parts that offset the part in question. With so many different faculties to work with, Gall could “prove” whatever he chose, and accordingly most scientists found his proofs worthless.8
But definitive refutation of phrenology came from the laboratory. Pierre Flourens (1794–1867), a brilliant young French physiologist, was aghast at Gall’s slipshod methodology and set out to discover, by experiment, whether specific psychological functions are, or are not, located in particular areas of the brain.9 A skilled surgeon, he operated on the brains of birds, rabbits, and dogs, removing small areas and carefully nursing the animals back to health to see how their behavior was altered by the loss of those areas.
He could not, of course, test for such human faculties as verbal memory, but he could test for faculties housed in portions of the brain that Gall himself said were comparable to those in human brains. One such was the “organ of amativeness,” supposedly located in the cerebellum (the primitive part of the brain, toward the back and base of the skull). When Flourens removed more and more of a dog’s cerebellum in a series of operations, the dog gradually lost the power of orderly movement until it would turn left when it wanted to turn right, fall backward when it wanted to go ahead, and so on. The function of the cerebellum, clearly, was the coordination of purposive movement rather than amativeness.
Similarly, Flourens found that the progressive removal of areas of the cortex in animals reduced their responses to sensory stimulation and their capacity to initiate action. A small lesion produced no specific effect, as it should have if phrenology were correct, but merely decreased the animal’s overall responsiveness to visual stimuli and its general level of activity. With more removal of the cortex, the animal would become more inert, until all responsiveness and self-initiated movement were gone; a totally decorticated bird, for instance, would not fly unless thrown into the air. Flourens concluded that perception, judgment, will, and memory were distributed throughout the cerebral cortex. Although he had found a gross localization of function in the brain—the cortex and the cerebellum did serve different purposes—the specific functions of each were apparently evenly distributed within each.
Gall’s pseudo-scientific theory thus led to the first experimental studies of the localization of brain functions. Moreover, his theory, though wrong in all its details, survived Flourens’s assault, since later cognitive neuroscientists, following Flourens’s lead, were able to identify particular areas of the brain as being responsible for visual perception, auditory perception, and motor control. Flourens was right that memory and thinking are distributed throughout the cortex, but a number of lower and even some higher mental processes are indeed localized.
The most striking instance of a high-level function carried out by a local area of the brain is language. In 1861, Leborgne, a fifty-one-year-old patient at the Bicêtre asylum in Paris, was transferred to the surgical ward, suffering from gangrene in his right leg. The surgeon, a young man named Paul Broca, questioned the patient about his ailment, but Leborgne could utter nothing in reply but the meaningless sound “tan. ”10 He communicated only by gestures and “tan, tan,” although if one failed to understand his gestures he could angrily blurt out, “Sacré nom de Dieu!” Broca learned that Tan, as he was known in the hospital, had come to the asylum twenty-one years earlier, when he lost the power of speech. He had remained otherwise intellectually normal, but after some years had slowly developed paralysis of the right arm and leg.
Tan died six days after arriving at the surgical ward. Broca performed an autopsy and found that an egg-sized area of the left side of the brain somewhat forward of the middle had been destroyed; there was almost no tissue in the center of the lesion, and around its edges the remaining tissue was softened. Based on Leborgne’s history, Broca concluded that the lesion had begun at what was now its center and that while it was still relatively small, it had completely destroyed Leborgne’s ability to speak; only later did its spread cause paralysis. Evidently, this small frontal-lobe area of the left hemisphere of the brain was the seat of speech. It has been known ever since as Broca’s Area.
A little over a dozen years later, a German physician, Carl Wernicke, similarly discovered that certain patients who spoke fluently but used many peculiar words and had difficulty understanding what was said to them had a lesion of another small area in the left hemisphere a few inches to the rear of Broca’s Area. It eventually became clear that Broca’s Area governs syntax (the structure of speech) and Wernicke’s Area, as the second one is known, semantics (the meaning of words). Both are needed for normal speech; a lesion of Broca’s Area impairs the ability to muster words but not understanding, a lesion of Wernicke’s Area leaves the sufferer capable of fluent but nonsensical speech and with impaired comprehension of language.11
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 igno
red 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 are made up of cells, the German physiologist Theodor Schwann advanced the idea that animal tissues, too, consist of cells. He identified one kind of nerve cell, and soon others demonstrated that brain cells consist of nuclei and long branches that reach and contact the branches of other brain cells.
—According to Descartes’s animal-spirits theory, impulses could flow in the nerve in either direction. According to the electrical model of nervous activity, current flowed in only one direction. Espousing the latter concept, between 1811 and 1822 Charles Bell, an English anatomist, and François Magendie, a French physiologist, working independently, cut different nerves in animals to see what functions were affected. Both men were able to show that the nervous system consists of sensory nerves in which the current is afferent, flowing toward the spinal cord and brain, and of motor nerves in which it is efferent, flowing from the brain and spinal cord toward the muscles and organs.
These and a number of other discoveries, combined with what was already known of the physics of light and color, produced a nineteenth-century explosion of research in the physiology of the sense organs and perception. This new psychology was a radically different approach from the theistic fantasies of Berkeley and the skepticism of Hume to the question of how the mind perceives the world around it. And although at first it could deal only with lower-level psychological processes, most of the new psychologists hoped that eventually higher-level ones would be explicable in similar terms. Emil Du Bois-Reymond, a German physiologist, wrote to a friend in 1842 that he and a colleague had taken a solemn oath to demonstrate the truth of the following creed:
No forces other than the common physical-chemical ones are active within the organism. In those cases which cannot at this time be explained by these forces, one must either find the specific ways or form of their action by means of the physical-mathematical method, or assume new forces, equal in dignity to the chemical-physical forces inherent in matter and reducible to the force of attraction and repulsion.14
Although the “new psychology,” as it became known, appeared in a number of countries, it made its strongest showing in Germany, in whose universities, according to the eminent English historian of psychology Leslie Spencer Hearnshaw, “scientific psychology was born.”15
Nor, he says, was this any accident. Until 1870, Germany comprised a multitude of kingdoms, duchies, and self-governing cities, and had created many more universities than any other European country. Moreover, after certain educational and social reforms of the early nineteenth century, German universities supplied their scientists and scholars with well-equipped laboratories for research in physics, chemistry, physiology, and other sciences.
In that atmosphere, even philosophers and psychologists in the Kantian tradition rejected Kant’s assertion that psychology could never be an experimental science. Others came to believe that even the invisible higher-level mental functions, observable only through volunteers’ reactions to stimuli, could be experimentally and validly investigated.
But first we will look at the mechanists—or, rather, since there were many of them, at a few whose work was both particularly important and typical of the movement.
Specific Nerve Energy: Müller
Johannes Müller (1801–1858) began in the philosophic tradition, broke away from it to become the first great modern physiologist, then drifted back to philosophy in an effort to answer questions about the soul that lay beyond his physiology.16 But the time of philosophic psychology was over; his physiological work had considerable influence on psychology, his philosophic work none.
Müller, born in Coblenz of middle-class parents, was extremely gifted, energetic, and driven by a compulsion to excel. He was also endowed with Byronic looks—tousled hair, a sensitive mouth, and piercing blue eyes. Having earned his medical degree in Berlin when he was twenty-one, he set aside his youthful fascination with the quasi-mystical nature-philosophy of Schelling and did such dazzling work in physiology and anatomy that the University of Bonn made him Professor Extraordinarius* at twenty-four and full professor at twenty-nine.
Müller labored so prodigiously at vivisection and animal experimentation in his early twenties that by the time he was twenty-five he had completed two fat books on the physiology of vision. But he was prey to a manic-depressive tendency, and at twenty-six, soon after becoming a professor and marrying his longtime fiancée, he fell into a severe depression and could neither work nor teach for five months. At thirty-nine, when others forged ahead of him in physiological research, he had a second attack of depression; at forty-seven, when he was at odds with the ideals of the Revolution of 1848, a third attack; and at fifty-seven, in 1858, a fourth attack that ended in his suicide.
Nearly all of Müller’s significant achievements in physiological psychology were made in his early years; by thirty-two, when he moved to the University of Berlin, he was losing interest in what he called “knife-happy” experimentation and turning instead toward zoology and comparative anatomy. He no longer believed that experimentation could solve the ultimate questions of life; his monumental Handbook of Physiology, though filled with his and others’ experimental findings, contained a philosophic discussion of the soul that could have been written a century earlier. In it, he waffled about whether the soul was simply the brain and nervous system in action or was a separate “vital force” that temporarily inhabits the body.
Of Müller’s vast number of discoveries about the nervous system, many of which helped establish physiological psychology, one had an especially profound influence. The early physiological psychologists thought that any sensory nerve could convey any kind of sensory data to the brain, much as a tube will carry whatever substance is pumped through it, but they could not explain why, for example, the optic nerve conveyed only visual images to the brain, and the aural nerves only sounds. Müller offered a persuasive theory. The nerves of each sensory system convey only one kind of data or, as he put it, a “specific energy or quality”: the optic nerves always and only sensations of light, the aural nerves always and only sensations of sound, other sense nerves always and only their sensations.
Müller had reached this conclusion through a series of anatom
ical studies of animals—plus a tiny and seemingly clinching experiment that he performed on himself. When he pressed his own closed eye, the pressure created not sound, smell, or taste but flashes of light. He stated his doctrine in these terms:
The sensation of sound is the peculiar “energy” or “quality” of the auditory nerve; the sensation of light or colors that of the optic nerve; and so of the other nerves of sense. The nerve of each sense seems capable of one determinate kind of sensation only, and not of those proper to the other organs of sense. Among the well-attested facts of physiology, not one supports the belief that one nerve of sense can assume the functions of another. The exaggeration of the sense of touch in the blind will not in these days be called seeing with the fingers; the accounts of the power of vision by the fingers and epigastrium [abdomen] appear to be mere fables, and instances in which it has purportedly been practiced, cases of deception.17
As William James would say more dramatically, “If we could splice the outer extremity of our optic nerves to our ears, and that of our auditory nerves to our eyes, we should hear the lightning and see the thunder.”18
As positive as Müller sounded about this, he debated with himself whether the specificity of the sensory systems resulted from the special quality of each set of nerves or of the region of the brain to which that set traveled. Possibly the area to which optic impulses were delivered interpreted them visually, the area to which aural nerves went as sound. “It is not known,” he wrote in the Handbook, “whether the essential cause of the peculiar ‘energy’ of each nerve of sense is seated in the nerve itself, or in the parts of the brain or spinal cord with which it is connected.”19 But Flourens’s view that the brain was completely generalized still dominated physiological thinking, and Müller opted for the theory of “specific nervous energies.”
