Nicholas Keynes Humphrey (born 27 March 1943) is an English neuropsychologist based in Cambridge, known for his work on the evolution of primate intelligence and consciousness.

Humphrey played a significant role in the anti-nuclear movement in the late 1970s and delivered the BBC Bronowski memorial lecture titled "Four Minutes to Midnight" in 1981.

He made the first single cell recordings from the superior colliculus of monkeys, and discovered the existence of a previously unsuspected capacity for vision after total lesions of the striate cortex.

He returned to Cambridge, to the Sub Department of Animal Behaviour in 1970, and there met Dian Fossey, who invited him to spend three months at her gorilla study camp in Rwanda.

His experience with the gorillas, and a subsequent visit to Richard Leakey's field-site on Lake Turkana, set Humphrey thinking about how cognitive skills – intelligence and consciousness – could have arisen as an adaption to social life.

In 1976 he wrote an essay titled "The Social Function of Intellect", which is widely regarded[citation needed] as one of the foundational works of evolutionary psychology and the basis for Machiavellian intelligence theory.

With Robert Lifton he edited an anthology of writings on war and peace, In a Dark Time, which was released in 1984 and was awarded the Martin Luther King Memorial Prize.

Over the last ten years Humphrey has been investigating the placebo effect, and has put forward a novel theory with John Skoyles of what he calls the "health management system" through which the brain has top-down control over the body's healing resources.

[5] National Life Stories conducted an oral history interview (C1672/12) with Nicholas Humphrey in 2016 for its Science and Religion collection held by the British Library.