Professor Jeffrey Gray, who has died aged 69, was one of the leading, and most highly cited, experimental psychologists in the UK. He had an extraordinarily wide range of professional interests - from the study of simple learning in the medicinal leech to theories of human consciousness, and from the translation of inaccessible Russian experimental work to the development of stem-cell transplantation for the treatment of brain damage.

He wholeheartedly pursued whatever information he needed, and was never embarrassed to ask straightforward questions when drawn into areas in which he was not yet expert. This intellectual courage was a great strength, enabling him to access and contribute to new ideas and technologies all his professional life. His research was very much concerned with big issues that were clinically relevant or conceptually challenging: anxiety (two books, each extending to a radically revised second edition); schizophrenia (one of the most highly cited papers ever written in the field); synaesthesia (something of a late arrival); and consciousness were all tackled, at levels that could range from the molecular to the philosophical. His work on neural transplants as a possible clinical treatment for brain damage led to the creation of a spin-out company, called ReNeuron.

Gray was born in the east end of London. His father was a tailor, but died when Jeffrey was only seven. He was brought up by his mother, who ran a haberdasher's shop. He took A-levels in Latin, Greek and history at Ilford County high school for boys, where he also won the school boxing championship. He undertook military service from 1952 until 1954, during which period he learned Russian, at the time a key interest for Army intelligence. He greatly admired the language teaching that he received, because he felt it taught him general principles which made it relatively easy for him to acquire other languages: in addition to Russian, he spoke French, Spanish, Italian and Persian, which was his wife's native language. He could as readily give a lecture in Russian; translate Mallarmé from French; negotiate a land sale with a Greek peasant; or conduct an interview in Persian on Iranian television.

The army taught him to type as well. It turned out that before a crucial typing test he had been told that those who did really well might be sent to Supreme Headquarters Allied Powers Europe (SHAPE) at Fontainebleau, whereas those who failed might be sent to Korea. He reported that his typing had quite suddenly dramatically improved.

Following military service, he took up a MacKinnon scholarship at Magdalen College, Oxford, with a place to read law. In the event he negotiated a switch to modern languages, obtaining a first in French and Spanish. He stayed on to take a second BA, this time in psychology and philosophy, which he completed in 1959. He managed to offset some of the financial costs by giving jive lessons, as well as by language teaching - he was approached by New College to become their French tutor when he was 23.

His postgraduate work both broadened and deepened his interests in psychology. In 1959-60 he undertook a course in clinical psychology at the institute of Psychiatry, in London, which led to the award of a Dip Psychol, with distinction, after which he stayed on at the institute to study for a PhD in the department of psychology, at that time headed by Professor Hans Eysenck. His PhD was awarded in 1964, and was a quite extraordinary work. Part was concerned with experimental studies of environmental, genetic and hormonal influences on emotional behaviour in animals, foreshadowing contemporary work in behavioural genetics; the other part presented translations of work from key Russian psychological laboratories, plus his own 300-page commentary on the Russian work. This component of the thesis was published as a book, Pavlov's Typology; the formidable Professor Stuart Sutherland regarded it as the best exegesis and clarification of Russian work to be produced by any western p! sychologist.

Later that year, Jeffrey was appointed to a university lectureship in experimental psychology at Oxford, and in 1965 was elected to an associated tutorial fellowship at University College. He remained at Oxford until he replaced Eysenck at the Institute of Psychiatry in 1983. He retired from the chair of psychology in 1999, but continued his experimental research as an emeritus professor, and spent a very happy and productive year at the Centre for Advanced Studies at Stanford University, California, where he essentially completed a new book on consciousness, due to appear very shortly.

From his earliest student days, he was immensely energetic, imaginative and productive. Where others might simply write some research articles and a review paper, he might well write a book, too. He received a president's award from the British Psychological Society in 1983, and became president of the Experimental Psychology Society in 1996 (and a lifetime honorary member in 1999).

His energy and enthusiasm were just as clear outside the laboratory. Throughout his life he loved drama - he directed the The Winter's Tale in the Deer Park at Magdalen, casting the young Dudley Moore as Autolycus - as well as dance, opera, jazz and the cinema. He also developed passions for skiing and horse riding. He had enjoyed a wonderful ski trip shortly before the final stage of his illness began: he thought he had never skied better. He is survived by his wife, Venus, and his four children, Ramin, Babak, Leila and Afsaneh.