Violation of expectancies produces more false positive reports in a word detection task in people scoring high in unusual experiences scale

Abstract

Psychotic-like experiences (hallucinations) were investigated in a non-clinical population in two word-recognition experiments concerned with expectancies. Participants were assessed psychometrically for their level of schizotypy, hallucination- and delusion-proneness. A word recognition task, during which words or non-words were presented on a fast-moving display, was employed. For some participants, incorrect expectancies concerning the rate of word occurrence during the word recognition task were established. The generation of expectancies produced a shift in the number of false positive identifications of words in the direction of the expectancies; high expectancies led to high numbers of false positives, and low expectancies led to low numbers of false positives. A range of psychometric measures were taken, and two in particular appeared to impact the results. High schizotypy scale produced a higher number of false positive in the condition where expectancies were violated. This effect was larger when high numbers of target stimuli were presented in conjunction with expectancies that there would be lower numbers of targets. This effect was not found with measures of delusions or schizotypal personalities. The results suggest that levels of expectancies, particularly in a sparse environment, are a factor influencing perception in hallucination prone subjects.