Perceptual learning of illusory contours and colour.

An adequate account of the phenomena of illusory contours (ICs) will require an understanding of the genesis of such effects. There are two main techniques used to study perceptual genesis: the first is to slow down the relevant perceptual processes and to study them during perceptual learning; the second employs tachistoscopic exposures and backward masking. To date the technique of perceptual learning has not been shown to be applicable in the case of ICs. Two experiments are reported in which perceptual learning is used to study ICs. It is demonstrated that subjects can learn to see, first, illusory contours and, second, illusory colour. The suggestion is made that although there may be different kinds of illusory phenomena which may arise in different ways, these may all depend upon a common set of mechanisms.