Visual discrimination of motion: Stimulus relationships at threshold and the question of luminance-time reciprocity

Quantitative descriptions, derived from an earlier empirical study, of threshold relationships among the principal stimulus variables for motion discrimination are presented, with emphasis on evaluating the influence of stimulus energy content. The present findings are compared with those of R, H. Brown (1955, 1957, 1958), who reported the applicability of luminance-time reciprocity to motion threshold for exposures shorter than 0.1 sec. It is demonstrated that such reciprocity is atypical of motion threshold, and that it represents limitations imposed by the requirements of target visibility rather than by motion discrimination itself. It is also shown that Brown’s data are predictable from the present equations.