Semantic expectations can induce false perceptions in hallucination-prone individuals

Recently, it has been proposed that exaggerated top-down processing may generate spontaneous perceptual output, and that this may constitute a cognitive predisposition toward hallucinations. In this experiment, we investigated whether hallucination proneness would be associated with increased auditory-verbal perceptual expectations, and at which processing level this occurs. From 351 undergraduate students screened for hallucination proneness, using the Launay-Slade Hallucination Scale (LSHS), 42 subjects were recruited for participation. Two word recognition tasks were administered, in which top-down influences on perception were manipulated through sentence context (semantic task) or auditory imagery (phonological task). Results revealed that LSHS scores were correlated with the number of semantically primed errors. Subjects with higher levels of hallucination proneness were more likely to report hearing a word that fits the sentence context, when it was not actually presented. This effect remained significant after controlling for general performance on the task. In contrast, hallucination proneness was not associated with phonologically primed errors. We conclude that aberrant top-down processing, particularly in the form of strong semantic expectations, may contribute to the experience of auditory-verbal hallucinations.