Social Class and Intelligence

This paper presents a procedure for identifying possible interaction effects of factors in distributions of intelligence test scores through the construction of analogs to the development of intelligence. The procedure is based on the Pascal triangle for generating coefficients in the binomial distribution, but incorporates a technique for modifying coefficients. The most adequate analog is one which produces coefficients identical to an empirical distribution while requiring the fewest modifications of elements in the Pascal triangle. The procedure was applied to IQ test data reported by Burt on London school children. In general, the analogs for these data suggest different effects of social class on intellectual development at the upper and lower IQ ranges. tT here is much disagreement over ways in which genetic and social factors interact to affect intelligence. Degree of intelligence, in turn, acts along with other factors to induce social mobility or to stabilize social class membership in a society. Burt suggests that IQ distributions in children among different social classes in modern urban societies can be explained largely by genetic factors in terms of Mendelian polygenic inheritance.1 On the other hand, after an analysis of children's IQ's according to paternal occupation, Halsey concludes that "the observed differences between social classes in measured intelligence are more likely to be explained by environmental rather than genetic factors."2 To be sure, neither Burt nor Halsey subscribes to an extreme genetic or environmental position. However, their disagreement emphasizes the fact that little is known about the developmental processes of intellectual abilities under different social conditions. The purpose of this paper is to suggest an approach which focuses upon interaction effects of factors in explaining the distribution of intelligence test scores. Most models of relationships between genetic variation, environmental factors, and degree of intelligence are based upon assumptions of homogeneity or similarity of effects throughout the range of intelligence.3 Reports of heritability, for example, describe the amount of the total variance in a population explained by genetic variance. Ordinarily, 60-80 percent of the variance in intelligence is attributed to heredity.4 It is possible, however, that the interaction between environment and genetic factors in human societies is of such complexity that their effects on degree of intelligence differ at various ranges of IQ and age. On the assumption that genetic and environmental factors vary in their joint effect on intellectual functioning at specific ranges of IQ and at particular times, a series of speculations regarding development of intelligence can be generated. To facilitate such speculation, this paper describes a procedure for devising analogs of the development of intelligence in a population. This procedure at1 Cyril Burt, "Intelligence and Social Mobility," British Journal of Statistical Psychology, 14 (1961), pp. 2-24 and "Class Differences in General Intelligence: III," British Journal of Statistical Psychology, 12 (1959), pp. 15-33. 2 A. H. Halsey, "Genetics, Social Structure and Intelligence," British Journal of Sociology, 9 (1958), pp. 15-28 and "Class Differences in General Intelligence: I," British Journal of Statistical Psychology, 12 (1959), pp. 1-4. 3 See John L. Fuller and W. Robert Thompson, Behavior Genetics (New York: John Wiley & Sons, 1958), pp. 62-68. 4 J. Conway, "Class Differences in General Intelligence: II," British Journal of Statistical Psychology, 12 (1959), pp. 5-14; S. G. Vanderberg, "The Hereditary Abilities Study: Hereditary Components in a Psychological Test Battery," Americamt Joutrnal of Hutman Genetics, 14 (1962), pp. 220-237. This content downloaded from 207.46.13.115 on Sat, 08 Oct 2016 05:31:13 UTC All use subject to http://about.jstor.org/terms