Perception of threat in schizophrenics with persecutory delusions: an investigation using visual scan paths
Background. Cognitive theories of persecutory delusions in schizophrenia include increased attention to threat and reduced re-appraisal of information during decision-making.
Methods. We employed visual scan path measurements, an ‘on-line’ marker of attention, in schizophrenic patients with persecutory delusions (N = 19), negative symptom- and medication-matched patients with non-persecutory delusions (N = 8), and normal controls (N = 18). Stimuli comprised black-and-white photographs of social scenes rated as depicting either neutral, ambiguous or overtly threatening activity. Foreground areas containing salient information with regard to the overall scene were rated independently as either threatening or non-threatening in both the overtly threatening and ambiguous scenes; all foreground areas were rated as non-threatening in the neutral scene.
Results. For the ambiguous scene only, schizophrenics with persecutory delusions directed gaze to less threatening areas, and, for all three scenes, demonstrated reduced re-appraisal of information compared with both control groups. All subjects showed similar viewing strategies for the overtly threatening and neutral scenes.
Conclusions. These findings suggest abnormal information gathering and evaluation in schizophrenics, specifically related to the presence of persecutory delusions. In particular, the results point to biased processing of contextual information in an ambiguous setting in these patients, and perhaps perception of threat in inappropriate places.
c1 Address for correspondence: Dr Mary L. Phillips, Department of Psychological Medicine, King's College School of Medicine and Dentistry, 103 Denmark Hill, London SE5 8AZ.