Schizophrenics' use of perceptual grouping in visual stimuli

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Title: Schizophrenics' use of perceptual grouping in visual stimuli
Author: Webster, David Carl
Abstract: This study investigated Place and Gilmore's (1980 ) proposal that schizophrenics are unable to perform the first stage in perceptual processing (perceptual grouping ) . An alternative hypothesis (the Selective Processing hypothesis ) was tested which states that , when explicit instructions are given , schizophrenics can respond to the organizational features in a display . Twelve schizophrenics and twelve normal subjects briefly viewed a series of target displays of lines . Next , subjects saw two alternative displays presented simultaneously in a forced -choice format ; they chose the display that was most similar to the target . Forced -choice displays showed one alternative that was identical to the target in number (a feature perceived by local analysis ) and another alternative that was identical to the target in organization (a feature perceived by global analysis ) . The subject's selection of one alternative indicated whether he had applied global or local perceptual analysis to the stimuli . Subjects were tested under three bias conditions : (1 ) an induced global bias to attend to the grouping of stimulus elements ; (2 ) an induced local bias to attend to the number of stimulus elements ; (3 ) a neutral bias . The Place and Gilmore hypothesis predicted that schizophrenics would consistently apply a local bias to the stimuli , and would be unable to adopt a global bias . The Selective Processing hypothesis predicted that schizophrenics would apply a local bias under the local and neutral bias conditions , but would apply a global bias when induced to do so . Both hypotheses predicted that normals would consistently apply a global bias . The results failed to support the Selective Processing hypothesis . They partially supported Place and Gilmore's (1980 ) hypothesis in that schizophrenics failed to respond to the induction of a global bias ; schizophrenics did respond to the induction of a local bias . Contrary to both hypotheses , normals could be induced to apply a local bias as well as a global bias . The findings also suggested that whether subjects use global or local processing is influenced by the total number of elements in a display , and possibly , by the way these elements are configured in space .
URI: http : / /hdl .handle .net /2346 /11142
Date: 1988-08

Citation

Webster, David Carl Schizophrenics' use of perceptual grouping in visual stimuli. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /11142 .

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