The gap effect in pro-saccades and anti-saccades in psychometric schizotypes

Schizophrenic patients and their first-degree relatives exhibit deficits in the anti-saccade task. In the present study, anti-saccade task performance was examined in subjects with 'high' and 'low' expressions of the schizotypal personality trait. For that purpose, the SPQ-G, the German adaptation of the Schizotypal Personality Questionnaire (SPQ; Raine, 1991), was filled in by 489 university students. Twenty and 21 participants with 'high' and 'low' SPQ-G scores, respectively, were compared with respect to saccadic eye movements elicited under the overlap and 200 ms gap conditions of the pro- and anti-saccade tasks. Each task block comprised 150 trials, 75 to either side in random order. The order of presentation of the task blocks was counterbalanced across the participants of each group. Saccadic reaction times were slower during the anti- as compared to the pro-saccade task and under the overlap as compared to the gap condition. Direction errors occurred almost exclusively during the anti-saccade task, express saccades mainly under the pro-saccadic gap condition. High-schizotypal participants did not differ significantly from low-schizotypal participants in any of these measures. While these results might suggest normal anti-saccade task performance in schizotypal personality as defined by the SPQ-G, the sampling strategy adopted in the present study is the more plausible explanation for the lack of group differences.