Richard Langton Gregory, CBE, FRS, FRSE (24 July 1923 – 17 May 2010) was a British psychologist and Professor of Neuropsychology at the University of Bristol.

He was the son of Christopher Clive Langton Gregory, the first director of the University of London Observatory, and his first wife, Helen Patricia (née Gibson).

In April 1993, he was the guest for BBC Radio 4's Desert Island Discs, where his favourite choice was Beethoven's Piano Sonata No.

Gregory's main contribution to the discipline was in the development of cognitive psychology, in particular that of "Perception as hypotheses", an approach which had its origin in the work of Hermann von Helmholtz (1821–1894) and his student Wilhelm Wundt (1832–1920).

Although this takes place on a quite different time-scale, and inside one head instead of a community, nevertheless, according to Gregory, perception shares many traits with scientific method.

Much in Gregory's work can be seen as a reply to Gibson's ideas, and as the incorporation of explicitly Bayesian concepts into the understanding of how sensory evidence is combined with pre-existing ("prior") beliefs.

[14] Gregory argued that optical illusions, such as the illusory contours in the Kanizsa triangle, demonstrated the Bayesian processing of perceptual information by the brain.