Recent work on the biological basis of intelligence has forced psychologists to reconsider the definition and conceptualization of "intelligence" widely accepted during the last fifty years. Work with the electroencephalograph, the averaged evoked potential, reaction time and other largely physiological and non-cognitive measures has resurrected the conception of intelligence which originated with Sir Francis Gallon, and has posed great problems for the conceptualization beginning with A. Binet, and still widely accepted.