Learning behavior of young children of contrasting socioeconomic backgrounds is examined in this study, which poses the question: what are the necessary or sufficient environmental conditions for the establishment of identifiable patterns of behavior? Socioeconomic level (SEL), the principal independent variable, was defined in terms of parental occupation, income and education. Three sets of experiments were conducted, with varying age groups from high- and low-SEL schools and preschool programs. The first set employed concept formation procedures, the second investigated reward preferences, and the final set considered degree of stimulus control, as a function of SEL and as an interaction between SEL and training. Results are presented in detail. It is noted that differences between behavior of high- and low-SEL subjects were not always instances of high-SEL children doing "better" than the low-SEL group. Another study, included in this volume, investigated the distribution of changes in performance of high- and low-SEL subjects on a standardized achievement test. Subjects were 2nd-, 4th- and 6th-grade children, tested in the fall and spring and again the following fall. Results showed that the discrepancy between performances of high- and low-SEL children continuously increases with grade level. It was also found that a "tailing-off" tendency in improvement rates from spring to fall is more pronounced for low-SEL children, indicating a need for summer school programs. (BF)