Equating for socioeconomic variables
In comparative studies of the mental abilities of racial groups, environmentalists are most insistent that the racial samples being compared on intelligence be matched, or otherwise equated, on indices of socioeconomic status (SES), which usually includes father's occupation, education of parents, income, quality of housing, and place of residence. When groups are thus 'equated' and a substantial mean IQ difference still shows up, it is claimed that not enough environmental factors were controlled. As one sociologist put it: '. . . the kinds of socioeconomic measures that have been used so far in attempting to control on environmental effects appear to omit awealth of cultural and psychological factors' . This is a testable hypothesis; it should be determined how much the cultural and psychological factors (assuming they can be specified and measured) add to the multiple R2 with IQ over and above the R2 yielded by good indices of SESe
But the whole notion of equating for SES, in the first place, involves what has been called the 'sociologist's fallacy'. This fallacy is seen in full bloom in one sociologist's criticism of studies of Negro-white IQ differences which equated the groups for SES or other environmental factors: 'Actually in most of the studies he [Jensen, 1969a] reports on, the most important environmental variable, the IQ of the parent, has not been equated at all' (Stinchcombe, 1969, p. 516). Apart from the strictly environmental effect of parental IQ, l it is obvious that, since IQ variance contains a large genetic component, equating groups for parental IQ means equating them for genetic factors more than for environmental
236 Educability and Group Differences factors. The same is true, though to a lesser degree, when we equate for SES. When typical Negro children are equated with white children on some index of SES, one is comparing a majority of the Negro population with some lower fraction of the white population. 2 The white comparison group, therefore, is not genetically representative of the entire white population but is genotypically (as well as environmentally) lower by some substantial degree. Thus, if one supposes one is equating only for environmental influences, equating on SES equates too much. The method would be a proper control of environmental factors if all children had been placed in their SES categories completely at random, in the nature of a true experiment. But as it is, SES classification is more a result than a cause of IQ variance.