Range estimates of distant visual stimuli

Os made magnitude estimations of the range of visual targets located at physical distances from a few hundred yards or less to more than 5 miles. The targets were at different elevations in different experiments so that O’s gaze varied from 0 to 90 deg. The targets were presented against the empty sky or against water. The Os were stationary in most experiments, but were in motion in one. Results show that the psychophysical functions are power functions whose exponents range from ca. 1.25 to 0.8, depending on the angle of the target above the horizontal. Background texture or O motion had no effect.