Story of Psychology - Morton Hunt [68]
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 anatomical 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