The statistical efficiency for detecting sinusoidal modulation of average dot density in random figures

Abstract

Abstract--The average density of randomly placed dots was modulated according to a spatial sinusoid and estimates were made of the signal/noise ratio (d’) of the sensory representation of the pattern from subjects ’ responses. This was compared with the signal/noise ratio of the targets, and the results are expressed as the efficiency (F) with which the statistical information in the targets is utilized. For single-barred gratings F can reach 50 % and it decreases as the number of bars increases. For many-barred gratings d ’ is an accelerating function of modulation depth. These results can be partly inter-preted in terms of a model using “and ” and “or ” operations to match the image with a caricature of the expected pattern that the subject holds in his mind