Our objectives are to clarify the effects of maturation on the amplitude and latency of evoked potentials obtained under three conditions of auditory stimulation: clicks machine-delivered at regular intervals, (2) irregular intervals; and (3) self-delivered by the subject. Five boys and five girls of average intelligence at ages 3, 5, 7, 9, 11, 13, 15, and 17 will serve as subjects. An earlier study showed a self-stimulation effect, that is that self-delivered clicks effected evoked reponse wave forms which had faster latencies and smaller amplitudes than those evoked by machine-delivered stimuli; and that the degree of self-stimulation effect was related to levels of intelligence. An additional 40 children at ages 9 and 17 years will be tested who have been shown by individual intelligence test scores to have above and below average levels of cognitive competence. Evoked response latency and amplitude data under the three conditions of stimulation will be analyzed for the identification of significant sex, age, and intelligence effects. BIBLIOGRAPHIC REFERENCE: Lodge A., Marcus, M.M. and Ramer, C.M., Neonatal Addiction: A Two Year Study, Part II - Behavioral and Electrophysiological characteristics of the addicted Neonate. Addicted Diseases: an International Journal 2 (2): 277-234 (1975). Reprinted in Perinatal Addiction, R.D. Harbison (ed.) Halsted Press, 1975.