Spatial limits to the detection of transpositional symmetry in dynamic dot textures.

If a set of random dots is translated along a uniform axis and superimposed on itself, then the resulting texture is seen to have three possible perceptual outcomes depending on the degree of translation: pairedness, striation, and randomness. Similar perceptual effects are obtained by plotting identical point-pairs randomly in space and uniformly over time. The threshold between striation and randomness in dynamic dot textures was investigated, since it represents a spatial limit to the detection of transpositional symmetry. This limit was found to vary as a function of three factors: stimulus field diameter, retinal eccentricity, and high frequency attenuation. The limit was found to be invariant over a fourfold range of texture density. It is proposed that the ability of the human visual system to detect correlations in dynamic transpositionally symmetric textures is the result of the activation of populations of orientationally selective cells identified in the mammalian visual cortex. It is also proposed that the limits to this ability could be related to the average size of the receptive fields of such cells within a given region of the retina.