Fixational errors for two-dimensional tracking tasks with black and complex backgrounds.
BACKGROUND
In low-level flight, pilots must track objects against an array of background objects. The purpose of this study was to determine what influence the objects in a flight simulator background have on catch-up saccades and overall fixational errors during head-free ocular tracking.


METHODS
Two experiments were performed. In Experiment 1, subjects tracked a two-dimensional target consisting of the sum of five sinusoids (frequencies 0.30-1.25 Hz) horizontally and six sinusoids (frequencies 0.24-1.25 Hz) vertically in three background conditions. In one condition, the background was black, in another condition the projected background was the Microsoft screensaver "Starfield Simulation," and in another condition the background was that seen from a helicopter during a flight recorded in the Microsoft 2000 Flight Simulator software. Experiment 2 was the same as Experiment 1, except the frequency of each target sinusoid was doubled.


RESULTS
Radial fixational errors were calculated. In Experiment 1, the mean errors were 3.73 +/- 0.57 degrees (black background), 3.75 +/- 0.57 degrees (starfield simulation), and 3.87 +/- 0.70 degrees (flight simulator). These values were not significantly different. In Experiment 2, the mean errors were 7.04 +/- 0.54degrees (black background), 7.04 +/- 0.38 degrees (starfield simulation), and 8.15 +/- 0.96 degrees (flight simulator). These values were significantly different.


CONCLUSIONS
The distractors of the starfield simulation and flight simulator background did not influence catch-up saccades (Experiment 1). In Experiment 2, the flight simulator background increased the mean fixational errors most likely by drawing attention from the target.
Fogt
Nick
N
College of Optometry, Ohio State University, 320 West Tenth Avenue, P.O. Box 182342, Columbus, OH 43218, USA. fogt.4@osu.edu
Lai
Nicky
N
D000328:Adult; D000337:Aerospace Medicine; D001288:Attention; D001359:Aviation; D005403:Fixation, Ocular / Q000502:physiology*; D019416:Head Movements / Q000502:physiology; D006801:Humans; D009039:Motion Perception / Q000502:physiology; D010775:Photic Stimulation; D012438:Saccades / Q000502:physiology