Story of Psychology - Morton Hunt [296]
Mental set, or the expectation of what one might see, was another topic of this kind of research. Bruner and Postman used the tachistoscope to show subjects very brief views of playing cards, most of which were standard but some of which were not, like a red four of spades. Habit and expectation caused twenty-seven of their twenty-eight subjects to see the abnormal cards as normal, but once the subjects knew about the cards, their mental set was changed and they made far fewer incorrect identifications.23
By 1949 such studies had become so numerous that psychologists, borrowing a term then current in women’s fashions, spoke of the New Look in perception research. For about a decade, the New Look flourished, amassing data on the extent to which needs, motives, memory, and mental sets affect perception. Then, lacking detailed theory with which to explain the processes through which this took place, the movement lost steam. Much later, perception researchers came up with a cognitive description (rather than a theory) of visual recognition processing, lumpily called “bottom-up, top-down,” that made sense of the accumulated data. In bottom-up processing the mind assembles the various bits of data coming in, achieving higher levels of recognition and meaning as it sees them fit together. But top-down processing, drawing on stored memory, context, and the like, may influence the lower levels of perception, either by making ambiguous information clear or by inducing a conception—or misconception—of what is being reported at the lower level. An often-cited example is the middle letter in each of these words:
FIGURE 28
Bottom-up processing alone would leave us unsure what we were seeing; context—top-down processing—leads us to see the first one as an H, the second one as an A, although they are identical. Similarly, in the ambiguous images we saw above in FIGURE 24, it is whatever top-down influence we choose to exert that yields what we finally see.)
After the New Look petered out, perception research revived with the advent of a new and powerful theory, information processing, which in the 1960s and 1970s was beginning to transform cognitive psychology with its vision of an orderly series of processes by which sensations are transformed into thought, and thought to action. This theory postulates (and provides experimental evidence of) the metamorphosis of sensory input in a sequence of steps, including very brief storage in the sense organ, encoding into nerve impulses, short term memory storage in the mind, rehearsal or linkage with known material, long-term memory storage, retrieval, and so on. The theory made it possible for psychologists to be specific about how the mind handles incoming sensory material, and it revived interest in the cognitive approach to perception. By the 1970s research in the field of cognition was proliferating, as we will see in a later chapter.
But by then many significant discoveries had been made about the physiology of perception. Ever since, the two styles of looking at looking, the physiological and the cognitive, have existed side by side, seemingly opposed to each other but in reality focused on different aspects of the same phenomena, as discussed from here on.
Seeing Form
How do we see the shapes of things? The question may seem absurd— how could we not see them? But the perception of form is neither automatic nor foolproof. We see a shadowy figure in the park at night and cannot tell whether it is a bush or a lurking person; we read a carelessly scrawled signature and do not know whether it starts with C, G, or O; we arrive home exhausted after a long flight, spot our car in the vast airport parking lot, and trudge toward it, only to find as we draw near that it is a lookalike of another make; we enjoy a jigsaw puzzle precisely because we find it challenging and rewarding to locate the piece that will fit into the edge