Detection of visual forms in space and time.

Stationary and moving target forms were composed of 5 equally spaced dots embedded in a background of 600 noise dots; the spatial and temporal separations between the target dots were varied independently. Target detectability decreased linearly with both spatial and temporal separations between the target dots. Detectability of both stationary and moving targets obeyed the same quantitative dependence on total separations, invariant under orientation in space-time. Detection also depended primarily on the relative density of the target and noise rather than on the absolute spatial or temporal separations between target dots. Thus, space and time had interchangeable effects on the detection of both stationary and moving targets.