The purpose of this chapter is to review studies dealing with perceptual processes in mental retardates. The goal is not to draw theoretical conclusions, nor point to the significance of any particular study. Theory is considered in other chapters. An attempt will be made, however, not only to review perceptual studies, but also to draw certain conclusions about the status of empirical studies in this area and to point to certain methodological issues of importance when doing perceptual research with retardates. Although this appears as a fairly straightforward task, two issues immediately demand attention: What is to be meant by (1) perceptual processes, and (2) mental retardation. There has been long and continuing debate on both counts. For the sake of presentation, therefore, the reviewer will arbitrarily delimit these areas without attempting to justify these particular delimitations as the only ones possible.
Over the past two decades, attention paid to perception has dramatically increased. It has been stimulated by issues such as the effects of needs or values on perceptual responses, the potency of stimulus qualities and cognitive attitudes in determining the extent of play of central factors, and more recently the question of what is learned in perceptual learning situations. At times perception has been defined quite narrowly, while at other times it is difficult to see the difference between what are called perceptual responses and responses usually described as reflecting personality functioning. The fact that the term "perception" has been used to refer to varying operations has led some to address themselves to the issue of definition and to caution others regarding some of the dangers inherent in too broad or loose a conceptualization.