This proposal is for continued support for a program of research that has explored the relationship between visual structure and attentional functioning in mentally retarded and nonretarded individuals. Because basic properties of multi-element stimulus arrays are intrinsically relational and are embedded in ubiquitous environmental contexts, the ability to detect interstimulus relations like similarity/dissimilarity is essential for adaptive attentional functioning. Although children who have low mental ages (both mentally retarded and young nonretarded children) typically exhibit markedly deficient performances on tasks that demand relational responding, the present investigators have demonstrated that appropriate modifications of the visual array, designed to increase the perceptual salience of relevant stimulus relationships, can rapidly facilitate the performances of mentally retarded individuals in such experimental contexts. Informed by the findings obtained concerning the effects of perceptual structure on stimulus detection, the investigators are now proposing to extend their approach to several new paradigms, including (a) an integration of oddity and match-to-sample methodologies, and (b) assessing the visual processing abilities of mentally retarded individuals at the critical preattentional stage. This """"""""front-end"""""""" perceptually-based approach of """"""""guiding"""""""" attention is based on manipulations that have been used successfully in much prior research, particularly that of the current investigators. The proposed studies involve an examination of a range of experimental contexts that share common perceptual variables (e.g., symmetry and contiguity), and assess the relative contribution of these variables to attentional and preattentional processing in individuals with and without mental retardation. The findings of the proposed studies are expected to inform both applied and theoretical issues with respect to the attentional functioning of individuals with mental retardation. The proposed experiments include an integration of oddity and match-to-sample methods (i. e., oddity-based comparison arrays) with implications for generalized performances and extension of that paradigm to the investigation of set size and spatial contiguity in the matching/oddity framework. In a match-to-sample paradigm, stimulus variables including stimulus structure, symmetry of stimulus pattern, and adjacency of elements will be investigated and an analysis of the relationship between stimulus inspection time and stimulus variables will be conducted. Experiments on visual search are proposed that address stimulus variables of element contiguity and symmetry, and are followed by an investigation of guided search. The remaining experiments proposed utilize random dot kinematograms to evaluate stimulus organization variables in motion-defined forms, as well as the influences of training on detection and motion direction discrimination.
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