In another long-term predictive study, Felsman and Vaillant (1987) followed a group of 456 inner-city men from early adolescence to middle life. Again it was found that intellectual ability was a poor predictor of success in living, and that other personality attributes, such as ego strength and demonstrations of early practical competence were far better predictors. Felsman and Vaillant summarized their findings on intellective ability as follows:.
While we found that IQ powerfully affected educational attainment and itself appeared to be enhanced by childhood environmental strengths (especially factors of adequate maternal affection and supervision), intelligence and parental socioeconomic status (SES) appeared relatively unimportant in overall midlife outcome. For example, 7% of men with IQs under 80 were unemployed for 10 or more years, but so were 7% of the men with IQs over 100. (p. 296).
This is not the place for a lengthy review of the vast amount of research that has been conducted on the relation of IQ to work performance. For present purposes, it is sufficient to note that the results have been mixed. Several studies have failed to and significant correlations between IQ and work performance, whereas others, such as those conducted by Terman and his colleagues on highly gifted children (e.g., Terman & Oden, 1947) and a number of large-scale studies on normal subjects in ordinary work situations recently reviewed by Hunter (1986) have reported correlations that are very impressive. However, a problem arises in interpreting such correlations for, as McClelland (1973) has pointed out, in the absence of controls for socioeconomic level, which is highly correlated with both IQ and credentialing, it is impossible to determine to what extent the correlations between IQ and job performance were mediated by social advantage.
In an edited book, Practical Intelligence: Nature and Origins of Competence in the Everyday World, Sternberg and Wagner (1986) present a variety of studies under headings such as "Intelligence on the Job," "Intelligence in Daily Life," "The Development of Practical Intelligence," and "Cross-Cultural Approaches to Practical Intelligence.