Cerebral lateralization of global-local processing in people with schizotypy

Patients with schizophrenia have been described as being poor at processing Gestalt aspects of stimuli, but efficient in processing their local aspects. The present study examined Gestalt processing in normal subjects classified according to the positive dimensions of schizotypy. It further explored whether the Gestalt deficit is due to a more fundamental deficit in rapid global processing which occurs at an early stage and precedes local processing. In addition, it was postulated that the right hemisphere should be more involved in dysfunctional global processing. Thirty-three normal individuals assessed as having high or low scores on schizotypy scales were asked to recall the name of a set of hierarchically formed letters in a divided visual field paradigm. The results support a deficit in involuntary rapid global processing and an underlying right-hemisphere dysfunction in high scorers on the unusual experiences' (UnEx) and STA scales of schizotypy. This indicates that in such subjects local stimuli excessively intrude into the processing of global information in the right hemisphere.