PURPOSE. Smooth pursuit eye movements are important in operating moving vehicles, where they might be utilized for instrument scanning or to track vehicles that may merge into the operator’s path. The purpose of this experiment was to determine whether a complex background influences smooth pursuit tracking. METHOD. Eight subjects participated. Subjects tracked a pseudo-random two-dimensional laser target (distance = 3.4m). The target was the sum of 6 sinusoids (0.24 to 1.25Hz) in the vertical and the sum of 5 sinusoids (0.37 to 1.25Hz) in the horizontal. Maximum amplitudes were 11 deg (vertical) and 15 deg (horizontal). In each trial, subjects pursued the target for 1 minute. Three conditions were performed randomly. In one trial, subjects tracked the target against a black background (Condition 1). In a second trial, subjects tracked the target against an optic (radial) flow field (Condition 2). In a third trial, subjects tracked the target against a complex background produced by playing back a recorded helicopter flight in the Microsoft 2000 Flight Simulator (Condition 3). The simulated view was from the cockpit (cockpit controls not visible), and a horizon and buildings on the ground were visible. Gaze signals were digitized at 200Hz using search coils.
RESULTS. The mean of the horizontal standard deviations of retinal position error (difference between right eye positions and target positions) was 2.79 deg (Condition 1), 2.94 deg (Condition 2) and 3.06 deg (Condition 3). Vertical values were 2.87 deg (Condition 1), 2.86 deg (Condition 2) and 2.98 deg (Condition 3). The differences in these values were not significant for the vertical (repeated measures ANOVA), although the horizontal differences approached significance (p = 0.092).
CONCLUSIONS. The simulated background had a mild detrimental effect on horizontal pursuit performance for some subjects. Subjects who were influenced by the simulated background may have been distracted by this BACKGROUND: The radial flow field had virtually no effect on pursuit performance compared to the black BACKGROUND: