The text of Volume 4 represents an international review of research in mental retardation dealing primarily with human and animal laboratory behavior. The contents range through the following topics: memory processes in retardates and normals by Norman Ellis; a theory of primary and secondary familial mental retardation by Arthur Jensen; inhibition deficits in retardate learning and attention by Laird Heal and John Johnson, Jr.; growth and decline of retardate intelligence by Mary Ann Fisher and David Zeaman; the measurement of intelligence by A.B. Silverstein; social psychology and mental retardation by Warner Wilson; mental retardation in animals by Gilbert Meier; and audiologic aspects of mental retardation by Lyle Lloyd. The papers represent knowledge in the field of behavior of the mentally retarded through the vehicle of interpretive reviews and theoretical invention. (CD)