Judgments Under Simulated Visual Space Conditions

1987 SUMMARY Thirty-jive volunteers responded when they first perceived an increase in apparent size o f a collimated, two-dimensional image of an Orbiter vehicle. The test variables of interest included the presence o f afixed angular reticle within the field of view (FOV); three initial Orbiter distances; three constant Orbiter approach velocities corresponding to 1.6, 0.8, and 0.4% of the initial distance per second; and two background starfield velocities. It was found that (1) at each initial range, increasing approach velocity led to a significantly larger distance between the eye and Orbiter image at threshold; (2) including the fixed reticle in the FOVproduced a significantly smaller distance between the eye and Orbiter image at threshold; and (3) increasing background star velocity during this judgment led to a significantly smaller distance between the eye and Orbiter image at threshold. The last two findings suggest that other detail within the FOV may compete for available attention which otherwise would be available for judging image expansion; thus, the target has to approach the observer nearer than otherwise if these details were present. These findings are discussed in relation to previous research and possible underlying mechanisms.