Schizoid personality, inter-hemispheric transfer, and left hemisphere over-activation.

This study assesses the external validity of schizoid personality against multiple measures of cerebral laterality designed to distinguish between left hemisphere (LH) over-activation, LH damage and inter-hemisphere transfer deficit interpretations of schizotypy. Questionnaire measures of schizoid personality were assessed in an undergraduate population and related to laterality measures of both verbal and nonverbal dichotic listening, haptic inter- and intra-manual matching, employment of left and right hemisphere strategies during the haptic task, lateral eye-movements, and left and right ear auditory thresholds. A high score on a composite index of schizoid personality was significantly related to greater asymmetry (right ear advantage) in verbal dichotic listening, the use of LH strategies, and lower right ear thresholds, an overall pattern of results indicating LH over-activation in schizoids. It is suggested that studies comparing schizophrenic patients with normal controls minimize the likelihood of obtaining group differences if they fail to take into account schizoid personality in the controls.