Size estimation in paranoid and nonparanoid schizophrenics.

Fifteen paranoid and 15 nonparanoid schizophrenics and 15 normal controls were administered a size estimation task which featured two administrations of nonthematic standard stimuli. The standard stimuli were presented under three conditions of background stimuli: a) surrounded by four smaller stimuli of the same kind; b) surrounded by four larger stimuli of the same kind; c) presented without background stimuli. Standard stimuli were presented at exposure times of 33 and 4000 milliseconds. On the first administration, nonparanoid schizophrenics were found to overestimate size relative to paranoidschizophrenics with normal controls intermediate in performance between the paranoid schizophrenics and nonparanoid schizophrenics, particularly on longer stimulus exposure times. The groups did not differ on the second administration. This replication of the results of earlier investigations suggest that the repeated administration of size estimation procedures in which the effects of sequence and thematic content stimuli were inextricably confounded may have contributed to recent conflicting findings in the size estimation literature. Contrary to predictions generated by Cromwell's stimulus redundancy formation, the paranoid schizophrenics were not more affected by the size of the background stimuli than the nonparanoid schizophrenics.