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

-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 manybarred gratings d’ is an accelerating function of modulation depth. These results can be partly interpreted 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.