Statistical efficiency for the detection of visual noise

Visual detection thresholds were measured for one-dimensional static noise patterns centered at 2 c/deg on a logarithmic scale, for several widths and spatial frequency bandwidths in the presence and absence of a one-dimensional dynamic visual noise mask. Human performance was compared with the ideal observer's performance for the same task. The ideal's contrast thresholds increase with the fourth root of bandwidth. For thresholds measured in the presence and absence of noise, the fourth-root-law for bandwidth fitted the human observers data from 1 to 6 octaves for a space constant of 2° and from 2 to 6 octaves for a space constant of 0.25°. Detection efficiencies were quite high (30-60%) for patterns of 1- and 6-octave bandwidths. These results can be interpreted either in terms of a channel with an adjustable spatial frequency bandwidth or as very efficient combination of information between spatial frequency channels.