Head movements in schizophrenia: new biological marker, critical neurological flaw, or artifact of subvocalization?

Findings (Kolada & Pitman, 1983; Pollack & Krieger, 1958; Stevens, 1977) that schizophrenics use a combination of head and eye movements while doing tasks in which normal subjects use only eye movements were replicated using reading materials with varied line lengths. Schizophrenics (N = 12) began making head movements during silent reading at an average visual angle of 15 degrees, whereas normal subjects (N = 42) began at an average angle of 19 degrees, (p < .05). No differences were found for reading out loud. Results for a checking task (p < .01) with the same sample and for a CRT reading task (p = .05) with a smaller sample (N = 14) also indicated more use of head movements by schizophrenic subjects. Literature is reviewed suggesting that these easily observable head movements may be an especially interesting focus for schizophrenia research because of their possible relationships to pursuit tracking, dopamine metabolism, cognitive activity, and subvocalization.