Middle-class youngsters outperform lower-class youngsters on most measures of academic ability and achievement (Jensen, 1969). There is considerable controversy as to why this is so; this controversy centers on the nature of the differences in intellectual functioning between middle-and lower-class youngsters. Two of the most prominent views regarding these differences have been presented by Arthur Jensen and William Rohwer, Jr.; the Jensen and Rohwer views, however, differ in important ways. The present study is aimed a t examining differences between these two views.
Arthur Jensen (1968) argues that intellectual tasks can be placed along a learning ability continuum which is the phenotypic expression of two functionally dependent but genotypically independent types of processes which he labels Level I and Level I1 mental abilities. Level I processes are associative and are best measured by tests such as digit span and serial rote learning. Level I1 processes involve transformations or complex operations performed on stimulus input and are best measured by tests such as the Progressive Matrices.
Jensen's theory states that Level I and Level I1 abilities are distributed differently in upper and lower socioeconomic status (SES) groups. Level I ability is distributed approximately the same in all SES groups, Level 11 ability is distributed about a higher mean in the upper-classes than in the lower. Jensen presents convincing evidence to the effect that low Level I1 ability accompanies low Level I ability in high-SES groups but not in low-SES groups. One implication of this finding is that a majority of youngsters in EMR classes in predominantly low-SES schools are not LLprimary'' retardates. Jensen argues that this is due to the fact that Level I1 measures, such as I& tests, are most often used in diagnosing mental