About 10 years ago, experimental psychology seemed to have little to offer for the analysis and solution of mental health problems. We all remember the joke about the psychologist searching under the lamp-post where the light was strongest. It is not repeated as often nowadays - and with good reason. Concepts from experimental psychology have come to play an increasingly central role in psychiatry. The following is an analysis of the percentage of articles in the British Journal of Psychiatry which were not concerned with psychiatric diagnosis, psychoanalysis, dynamic psychotherapy, physical therapies, neurology, epidemiology, genetics, prognosis and aetiology of syndromes, in the years 1966, 1970, 1973. Psychometric and psychophysiological studies were also excluded if they related to differential diagnosis of psychiatric states. The figures were 11, 13 and 23% for the three years, suggesting a slowly accelerating utilization of concepts derived from experimental psychology. If the rate of growth continues, models derived from experimental psychology will be dominant by 1980.