Distance judgment by the method of fractionation.

Abstract
The present study is an application of a psychological scaling operation (fractionation) to perceived distance. A 300-yd. stretch of grass-covered flat ground was used for O''s judgments. A bicyle moved up or down this stretch, and O indicated his judgment by stopping the rider at what he considered the correct division point. Six bisections and four trisections were made, with different intervals and ground stretches so chosen that one of the true division points would lie every 25 yd. from zero (O''s station point) through the 250-yd. point. The results suggest the following conclusions: 1). Observers can divide stretches of distance (up to 300 yd.) into halves or thirds with very good accuracy. Perceived magnitudes of distance appear to correspond well with physical magnitudes of distance. There is no tendency for the judgments to follow a hypothetical curve which would result from their being based on the magnitude of the visual angle subtended by different distance stretches. (3) Error is related to the direction of motion of the target; the CE tends to be positive as the bicycle approaches, and either less positive or negative when the bicycle withdraws. Fractionation of distances was not improved by correction O''s errors, nor was variability reduced.