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18. What Are Intermediate-Level Visual Features?

Steven W. Zucker

Subject Psychology

DOI: 10.1111/b.9781119954682.2013.00021.x


Before the middle of the last century, it was difficult to relate the theoretical, phenomenological, psychophysical, and neurophysiological levels of visual analysis. Each had their own language, their own explanatory style, and their own data. This all changed as the concept of a visual feature solidified. Specifying “what the frog's eye tells the frog's brain,” paraphrasing the title of Lettvin's ( Lettvin, Maturana, McCulloch, & Pitts, 1959 ) seminal paper, showed how features could be viewed as maps from image fragments, or their neural realization, to higher levels, thus forming the basis for visual representation hierarchies. At the top of the hierarchy was a classifier, for example, to identify when a putative fly is in range. Although the hierarchies under consideration in mammalian and primate visual systems are now much deeper than that for the frog, by and large this view still predominates, especially for object recognition. However, a problem arises when one considers the more abstract issues revealed by the Gestalt psychologists, for example figure–ground. These are not features with local support, such as the dark moving spot depicting a fly, nor do they fit naturally within standard views of the feedforward visual hierarchy. General vision requires much more perceptual organization; it implies an interplay between bottom-up and top-down issues. The visual system ... log in or subscribe to read full text

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