MUELLER-LYER ILLUSION AND SIZE ESTIMATION PERFORMANCE IN SCHIZOPHRENICS COMPARED TO NORMAL CONTROLS

A size estimation (SE) paradigm and the Mueller-Lyer (ML) illusion wer e used to examine perceptual disturbances in schizophrenics. 35 reliab ly diagnosed (DSM III-R) schizophrenics were compared to 20 subjects w ith no history of psychiatric illness, Perceptual distortions found in previous studies of schizophrenics were only to a certain extent conf irmed in the present results. More overestimators were found among the schizophrenics than among the normals on the SE task. The schizophren ics, first of all the chronic patients, also proved to be more prone t o the Mueller-Lyer illusion. A reason why the very clear differences b etween schizophrenics and normals found in previous examinations were not confirmed in the present study, might be that a reliable diagnosti c instrument was for the first time used in this kind of study.