This revised application seeks support for an investigation of the preattentional processing abilities of individuals with and without mental retardation. Preattentional processing, in the present context, refers to the early stages of visual processing that operate prior to cognitive or attentional influence. Particular attention is given to the fundamental visual dimensions of color, form, and motion. These dimensions are believed to be processed by separate precortical visual pathways (e.g., Livingstone & Hubel, 1988), and to serve as particularly important bases for image segmentation and recovery of depth information. The importance of these early stages of visual processing lies in the fact that their outputs serve as the basis for perception and cognition. If the preattentive processes of individuals with and without mental retardation do not operate identically, then the higher processing centers will not receive identical input. The differential informational input for attentional processing would be expected to have dramatic and widespread consequences for behavior. Recent studies (Carlin et al., 1995; Fox & Oross, 1990; 1992) have indicated that individuals with mental retardation do not process visual stimuli preattentively in the same manner as individuals without mental retardation. Such differences have been identified across experimental tasks as varied as visual search and detection of motion-defined forms (i.e., random dot kinematograms). These findings, if found to be reliable and general, would have import for theoretical discussions of the bases for intelligence-related differences on various experimental tasks, as well as applied relevance for the design of optimal learning environments and training procedures. In summary, this application seeks to (a) assess the preattentional processing abilities of individuals with mental retardation comprehensively, (b) determine the modifiability of identified deficits via perceptual training procedures or manipulations of stimulus structure (cf. Soraci & Carlin, 1992), and (c) assess "front-end" manipulations of stimulus structure and their effect on higher-order processing (e.g., matching to sample).