Visual perception in a natural context operates on an optic field that consists neither of a random luminance distribution nor of a rigidly structured pattern.
Spontaneous structure is stochastic rather than exact.
To degrade regularity we varied the position of each dot according to a normal density function centred on the corresponding location in the dot lattice. Using this technique we investigated the effect of stochastic perturbation on perceptual organisation. In the present experiments, we asked observers to indicate the orientation of grouping perceived in perturbed dot lattices presented for 300 ms. Our data show that the greatest effect of the degradation of regularity is due to a loss of collinearity. The results are considered in terms of the pure distance law, the interaction between Gestalt laws, and the relation between perceptual organisation and detection.