Feature Integration Theory

Neuropsychological Evidence

What sort of evidence has been marshaled to support this view? The answer is many and varied, but here the focus is with data from neuropsychology. Consider, for instance, the variety of different forms of color blindness. Although most cases can be attributed to problems in the eyes, with cerebral achromatopsia the problems are caused by damage or injury to particular areas of the visual cortex. In such cases, the world appears to be drained of color—there is a selective deficit in processing color—but other visual abilities such as perceiving shapes, depth, and motion remain intact.

More startling perhaps and much more rare are individuals who have problems in being able to see motion following damage to the brain. Josef Zihl and colleagues described the most famous case, labeling the condition motion blindness. The unfortunate individual suffered a stroke that resulted in bilateral damage to the posterior parietotemporal and occipital regions of her cortex. She was described as inhabiting a kind of stroboscopic stop/start world in which things were never seen in motion but were simply here and there. Less severe cases also exhibit selective problems with motion perception even though the ability to perceive other visual characteristics remains intact. Such evidence suggests specific brain mechanisms dedicated to perceiving color and motion, respectively.

A different and fascinating case undermines the notion that analyses of shape and color are inextricably interwoven. When presented with three vertical bars colored red, white, red, respectively, or black, red, black, respectively, the individual reproduced these displays by drawing a large red rectangular blob. In other words, this person experienced great difficulties in linking a red filled-in region with its bounded contour. His perception of these sorts of pictures reflected the fact that the color seeped out from the corresponding red areas and did not honor the areas' actual boundaries. This counterintuitive finding suggests that the brain invokes independent analyzers for color and shape, respectively, despite the compelling impression of solid objects with associated colored parts. This interesting case was documented before the recent advances in brain imaging; hence, it was impossible to know the exact cause of the problems. However, tests ruled out any kind of retinal deficit, and there was no evidence of acquired brain damage. The problems seemed to reflect the development of a brain in which the cortical regions responsible for color processing were disordered.

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