Content of Perceptual Experience

Suppose a subject recognizes George Washington on a dollar bill. It is an open question whether this is part of the subject's perceptual (in this case, visual) experience that the person depicted is George Washington, or whether all that is visually experienced are colors and shapes, with the judgment that it is George Washington occurring farther downstream (later in the perceptual system). According to Thin views about the contents of visual experience, these contents are limited to color, shape and illumination. According to Rich views, the contents of visual experience can involve more complex high-level features in addition to color, shape, and illumination, such as personal identity (George Washington), kinds (banana, truck), semantic properties (meanings of words), and causation. Rich views thus posit more informational richness in the contents of visual experience than do Thin views. If Rich views are correct, then even if some visual experiences are thin (such as the experience of looking out of an airplane window into a clear blue sky, with nothing else in your peripheral visual field), visual experiences can represent that someone is George Washington, or that an object is a truck, or that the ball's collision with the apple caused the apple to move. If Thin views are correct, in contrast, then visual experiences can represent only that there is a layout of colored shapes, variously illuminated, where some part may be moving.

The debate between Thin and Rich views affects the search for neural correlates of visual consciousness. Antecedently held assumptions about whether visual experience is Rich or Thin may influence what researchers are prepared to count as a neural correlate of visual consciousness. If contents are Thin, then the neural correlates are more likely to be limited to early visual areas, such as V1 or V5. If contents are Rich, then the neural correlates are more likely to involve later areas, such as the inferotemporal cortex and the fusiform face area.

The debate between Rich and Thin views interests psychologists because it is relevant to what the neural correlates of visual consciousness are, and on what cognitive processes are inputs to the underlying structures that give rise to visual consciousness. It is also relevant to the structure of disorders such as agnosia, in which subjects can see ordinary objects but cannot recognize them. If the Rich view is true, then agnosia may involve impoverished visual consciousness. If the Thin view is true, then agnosia may be a disorder downstream of visual consciousness, rather than a disorder involving visual consciousness itself. Finally, the debate is relevant to the cognitive structure of delusions such as Capgras syndrome, in which patients take a loved one to be an impostor. If a Rich view is true, so that visual experiences may represent such properties as “being an impostor,” then Capgras syndrome may be a normal response to an abnormal experience, consisting in taking things to be the way they appear in the (abnormal) experience. If a Thin view is true, in contrast, whether or not the visual experience of Capgras sufferers is itself abnormal, the response to the experience almost certainly is abnormal. In that case, the disorder would consist of the abnormal response to evidence, perhaps in addition to an abnormal evidential base.

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