Large colour differences measured by spontaneous gestalt formation

Gestalt formation is used as a means to measure large colour differences. The stimulus is presented in the form of the Star of David, being made of two overlapping triangles of different colour, with the overlap being in a third colour. Through Gestalt formation the subjects perceive a triangle pointing to the left or to the right. Gestalt formation is assumed to occur for colour combinations with the smallest perceptual distance. We simulated responses at the ordinal level with several uniform‐colour‐distance models, derived from near‐threshold colour‐discrimination experiments. For isoluminant colours 84% of the responses, and for nonisoluminant colours 76% of the responses, are predicted correctly by the best model. We argue that the tritanopic direction is crucial for the understanding of large‐colour‐difference data.