Story of Psychology - Morton Hunt [293]
More precise pinpointing of the visual cortex was a byproduct of weaponry used in the Russo-Japanese War of 1904–1905.11 In that conflict the Russians introduced a new rifle, the Mosin-Nagant Model 91, which fired bullets of smaller diameter and higher velocity than the rifles of earlier wars. The bullets often penetrated the skull without shattering it, and in some cases destroyed, partly or totally, the victim’s vision without killing him. Tatsuji Inouye, a young Japanese army doctor who worked with wounded soldiers, plotted the extent to which each patient’s visual field had been lost by each eye, determined from the site of the bullet’s entry and exit which parts of the brain had been damaged, and, putting these data together, identified the precise location and extent of the visual cortex.
Among his findings was that the areas of the visual cortex that receive the retinal messages are grossly disproportionate to the areas of the retinal image. A very large part receives impulses coming from the fovea, the small central area of the retina where vision is sharpest, and only a small part from the larger peripheral area. (Later research showed the disparity in proportions to be about 35 to 1.12) That settled one great issue: what arrives at the brain is in no way an image corresponding in layout to the image on the retina.
The inescapable implication of Inouye’s and others’ findings, gradually accepted over the next several decades, was that the retinal cells are “transducers” that change light signals into a different form of energy— bursts of nerve impulse—and that these “coded” impulses or signals, when received in the brain, are not turned back into images in the visual cortex, even though “seen” there or elsewhere in the brain.13 How they are seen remained a mystery, but perception physiologists did not trouble themselves with this question; their style of looking at looking dealt with the flow of neural impulses and stopped short at the borders of mind.
Another style of so-called perception research—it was only peripheral to perception—was in the Wundtian tradition. Its practitioners studied sensations (the immediate simple responses to sounds, lights, and touches), which they considered reflexive, elemental, and scientifically investigable, and the perception of those simple sensations. But they ignored all the complex interpretive aspects of perception, which they correctly deemed the result of the mind’s processing of sensations and incorrectly believed to be beyond objective scrutiny. This approach, popular in the early part of the twentieth century, yielded a huge store of data about sensations but added almost nothing to the understanding of the psychology of perception.
Yet another style of perception research is psychophysics, which also stops short of looking at mental processes. Fechner and his followers, as we saw, measured sensory thresholds (the weakest sound, light, or other stimulus a subject could perceive) and “just noticeable differences” between pairs of stimuli. While such inquiries touched on conscious mental processes, the psychophysicists asked no questions about how the subject noticed a stimulus or judged differences but stuck to objective data—the magnitude of the stimuli and the subject’s statements that he did or did not perceive a stimulus or a difference between two stimuli. Psychophysics was therefore acceptable during the dominance of behaviorism, when perception was otherwise largely ignored because it assumes that a representation of the world exists in the mind, a concept the behaviorists