Mnemonic intrusions into working memory in psychometrically identified schizotypal individuals

Reduced working memory capacity seems to characterize the memory system of individuals from the schizophrenia spectrum. A probabilistic category learning task was designed in order to empirically test the hypothesis that deficient inhibitory control over the contents of working memory may be a fundamental cognitive abnormality of psychometrically identified schizotypal individuals. Two groups of participants were recruited on the basis of their responses on scales measuring psychotic-like experiences in a self-report schizotypy questionnaire. Simple stimuli were presented visually, and participants were instructed to glean the strength of the connection between pairs of stimuli. The experimental task comprised several learning conditions which were designed to assess predictions derived from the inhibition-deficit hypothesis. Working memory-dependent and working memory-independent task conditions allowed to examine the specificity of the putative inhibition deficit. The subjective strength of connections between pairs of stimuli was doubly dissociated as a function of schizotypy (low scorers, high scorers) and learning condition (discriminative, non-discriminative), but only when there was a delay between the to-be-associated stimuli, i.e. when the task was working memory-dependent. The pattern of results is consistent with the inhibition-deficit hypothesis which conjectures that the flow of information through short-term memory features one serious flaw in individuals from the schizophrenia spectrum, namely the occurrence of mnemonic intrusions from long-term memory into working memory.