BRlSLlNcepts is demonstrated by showing how they relate to such important topics as education, health, interpersonal relations, and child rearing practices.Of course, social class, ethnicity, culture, and race do not exhaust the major concepts summarizing influences on human diversity. Others have been reviewed in previously published G. Stanley Hall collections: age (Kagan, 1985;Schlossberg, 1984); sex (Denmark, 1983); psychological abnormalities (Sarason, 1983); and the physical environment in which people find themselves (Saegert, 1986;Stokols, 1982). As with the four concepts examined in this chapter, many psychological phenomena can be understood only when viewed in the context of other factors. For instance, a person's age, sex, social class, cultural background, and current environment all affect obesity and a person's attitude toward and ease in losing weight (Brownell, 1982;Grunberg, 1982;Rodin, 1981). Yet there has to be a starting point for introducing these topics to students, and the best teaching method ma): be to treat them one at a time and later to cover combinations of and interactions among the four concepts.This chapter has three major parts. In the first, the concepts of class, ethnicity, culture, and race will be explained. Further, research will be reviewed that points out important relations between and among these four concepts and such dependent variables as educational achievement, health, interpersonal relationships, and child rearing practices. For all four concepts, the point will be made that the general label (e.g., class) is almost always too broad for a helpful analysis of human behavior. Rather than accepting the general label as having explanatory use, a better practice is to ask what more specific independent variables (e.g.. number of books in the home, which is partly affected by parental income) have an impact on dependent variables (e.g., progress in reading in school).In a second section, research will be reviewed that requires understanding of two or more of the concepts. In addition, other research areas will be reviewed that have suffered because of faulty understanding of the four concepts. To preview one conclusion, many research findings have found a purported relationship between race (especially Black-White differences) and educational achievement (reviewed by Katz, 1973, who is sensitive to the dangers of facile conclusions concerning supposed racial differences). Such findings disappear or become much smaller in magnitude when the class background of students is assessed (e. g., Bardouille-Crema, Black, and Feldhusen, 1986). That is, the largest differences are often between middle-class and working-class Whites, or between middleand working-class Blacks, rather than between students who happen to have different skin colors.A third section will consider the four concepts as social categories individuals use to think about other people and how to behave 142