ABSTRACT
One of the most intriguing findings to emerge from the psychopathology literature in the last 2 decades involves the discovery of an association between abnormal smooth-pursuit eye tracking and schizophrenia (Holzman, Proctor, & Hughes, 1973). Smooth-pursuit eye movements are generated when the eyes follow a slowly moving target (e.g., less than 40 ° per sec) that is in continuous motion. One way they can be elicited is by requiring a person to track a swinging pendulum. In the normal smooth-pursuit system, the eyes lock on the target and duplicate its pattern of movement. In the case of pendulum tracking, a recording of horizontal eye movements will generate a continuous series of sine waves. For some reason, schizophrenic patients cannot do this very simple task; the sine waves evident in recordings of their eye movements are distorted in various ways (see Fig. 5.1). The inability of many schizophrenic persons to produce intact smooth eye movements now represents a robust finding that has been replicated in a large number of studies conducted in laboratories around the world.
