Constraints on perceptual learning: objects and dimensions.

The article addresses two questions about perceptual learning: What are the circumstances which produce learning? What is the content of learning? For each question, a critical principle is suggested: (1) Objects are constrained to behave in certain ways. If a violation is detected, an internal malfunction is assumed and subsequently corrected. (2) Learning involves mappings between entire perceptual dimensions rather than associations between individual stimuli. The principles are applied to two phenomena: the classic adaptation to prism distorted vision and the more recent, but equally elusive, McCollough effect. The view suggests a new interpretation of the McCollough effect and accounts for findings difficult to account for in other interpretations including which stimuli can successfully lead to contingent after-effects, the outcome of correlation manipulations, and why the effect exists at all. In addition, the phenomenon is linked to prism adaptation, usually regarded as a distinct type of plasticity. In general, the view advanced is that the two principles help distinguish perceptual learning from other types of learning processes.