Interaction of Level I and Level II abilities with race and socioeconomic status.

Two levels of mental abilities were hypothesized to interact with sooioeconomic status and/or race such that (a) socioeconomic-status differences were greater for Level II than for Level I abilities and (6) the correlation between Levels I and II and the regression of Level I upon Level II were greater in upper- than in lower-socioeconomicstatus populations. These hypotheses were borne out by the present data, consisting of Level I measures (digit-span memory) and Level II measures (Lorge-Thorndike Intelligence Tests, verbal and nonverbal) obtained on all white and black pupils in Grades 4-6 in one school district. The largest effects were attributable to differences between the white population and the low-socioeconomic-statusblack group. The present study tests Jensen's Level ILevel II theory of mental abilities in a total school population. The theory has been tested heretofore only with specially selected samples from the population. The theory and related evidence have been presented in detail elsewhere (Jensen, 1968, 1969, pp. 109-117, 1970a, 1970b, 1973, pp. 193-293; Jensen it is the capacity to register and retrieve information with fidelity and is characterized essentially by a relative lack of transformation, conceptual coding, or other mental manipulation intervening between