Perceptual biases and positive schizotypy: The role of perceptual load

The study investigated the effects of perceptual load on the bias to report seeing non-existing events—a bias associated with positive symptoms of schizophrenia and positive schizotypal symptoms. Undergraduate students completed psychometric measures of schizotypy and were asked to detect fast moving words among non-words under different levels of perceptual load. Perceptual load was manipulated through stimulus motion. Overall, the results showed that the higher the perceptual load, the stronger the bias to report seeing words in non-word trials. However, the observed bias was associated with positive schizotypy (Unusual Experiences) only when visual detection was performed under conditions of medium perceptual load. No schizotypy measure was associated with accuracy. The results suggest that, although some amount of perceptual ambiguity seems to be necessary for schizotypal bias generation, an increase in the perceptual load can inhibit this process possibly by preventing perception of task-irrelevant internal events, such as loose word associations. 2006 Elsevier Ltd. All rights reserved.