Stage-dependent sensitivity to Müller-Lyer visual illusion in schizophrenia patients

Schizophrenic patients show perceptual deficits, which may be detected in visual illusion tasks. Previous studies found that chronic patients show increased sensitivity to Müller-Lyer illusion as the disorder progresses, although there are a few conflicting reports in the scientific literature. To address these issues, moderate and chronic schizophrenic patients were tested on the Brentano version of the Müller-Lyer illusion task. Their performance was compared to first-degree relatives and unrelated matched controls. Chronic patients showed increased susceptibility to the illusion. Performance on the visual illusion task was not correlated to the number of years since disease onset, medication or (Positive and Negative Syndrome Scale) PANSS scores. The lack of association between illusion sensitivity and PANSS score may reflect the absence of the perceptual dimension in this scale. Based on these results, we suggest that susceptibility to the Müller-Lyer illusion is associated with the stage of schizophrenia rather than disease length.