Story of Psychology - Morton Hunt [297]
Research on form perception seeks to identify the mechanisms, both neural and cognitive, that enable us to recognize shapes—and that sometimes fail us. Much of that research in the past half century has taken the cognitive approach. The Gestaltists and their followers explored the mind’s tendency to group related elements into coherent forms, fill in gaps in what we see, distinguish figures from background, and so on. They and others also said it was inborn higher mental processes that account for the “constancy phenomenon”—our seeing things as unchanged despite distortions of the retinal image, as when we perceive a book lying at an angle to us as having square corners although on the retina, as in a photograph, the book is a rhomboid with two acute and two obtuse angles.
But such perceptions are results, not processes. By what steps does the mind achieve them? It is one thing to say that we fill in gaps in familiar but incomplete forms that we see; it is quite another to determine by what specific means we achieve this. Many studies exploring cognitive processing of visual information in fine detail have identified some of them. A few examples of the findings:
—Research on the subjective-contour phenomenon (as in the illusory triangle in FIGURE 25 above) indicates that we create the imagined contours partly through association (the three angles remind us of previously seen triangles) and partly through clues that experience has taught us signify interposition (an object’s obstructing our view of another one). As the perception researcher Stanley Coren pointed out, the gaps in the circles and in the existing triangle suggest that something else—the illusory triangle—is in the way, partially obscuring them. Because of the apparent interposition, the mind “sees” the imaginary triangle.24
—Some experiments have explored how we recognize a shape we are searching for, particularly when it is lost in a jumble of other shapes. One important process is “feature detection”—conscious searching for known and recognizable elements of a particular figure so as to distinguish it from similar shapes. In each of the following columns there is a single X. If you time your own search for it with a sweep-second hand, you will find that you locate it far faster in the first list than in the second:25
ORDQCG WEFIMZ
CRUDOQ EVLMZW
QUORDC VIMWZE
CUORCD ZIVFEW
DROCUD VIZELM
DOCURD MFWIVZ
DRGCOD ZVXIEW
ORCDUQ WVLZIE
ODQRUC EWMZFI
DRXOQU MEZFIV
DUGQOR IWEMVZ
RGODUC WEZMFV
GCUDOC EFLMIV
DGOCDR WZIEFV
The task of matching the pattern of the X retrieved from memory to what we are looking at is far easier and quicker when the hidden X is among rounded letters than among letters made up of straight lines and angles, like the X itself, in which case we must pay close attention to minor features. Or, as another explanation has it, we often identify visual images by “preattentive” processes—automatic ones concerned with overall image—but when that does not suffice, we shift to “focused attention” and consciously search for minor distinguishing features of the sought object.26
—In 1954 Fred Attneave, of the University of Oregon, asked subjects to represent certain figures by a series of ten dots; they tended to place the dots on those points where the direction of the outline changed most sharply. Attneave’s conclusion was that one way we recognize patterns is by means of analysis of its “points of change.”27 He also created some figures, greatly simplified from reality, by drawing straight lines from one point of change to another. Although this reduces curves to straight lines, the figures are still immediately recognizable, as in this example:
FIGURE 29
No curve exists, yet one sees a curved object.
—Skilled readers see words as wholes, without identifying them letter by letter, as beginning readers do. But even in rapid reading, a great deal of high-speed feature detection goes on, as shown by experiments conducted by Eleanor J. Gibson (the wife of James Gibson, mentioned above) and colleagues at Cornell