 to the SAT which was all multiple choice. Gender differences favoring males appears larger on those tests which are multiple-choice, which has been observed in earlier studies.
Socioeconomic classIntelligence differences between socioeconomic classes are well documented. In fact, one researcher (Tyler, 1956) concluded that the relationship of IQ scores to socioeconomic level was one of the best documented facts in mental test history. This was indicated earlier in Terman's study of gifted children, and more evidence will be presented in the next module. On the average, higher IQ's are found in families of the upper socioeconomic levels than in those of the lower levels.
IQ scores reflect educational opportunities. This is indicated in the data on socioeconomic levels. Children from disadvantaged groups frequently have inferior educational facilities, and their attitudes toward education are less favorable. The educational opportunities among various racial groups vary markedly. Therefore, one would expect that differences in average IQ would be apparent between various racial groups. Usually it is not really possible to determine whether the differences are due to racial or socioeconomic factors. Tulkin and Nembrough (1968) used statistical procedures to control for differences in such variables as broken homes, maternal employment, crowded living quarters, and so on. Under these controls their studies with upper social class grade school children indicated no difference between races.
Race differences. Many comparisons have been made between black and white children. Three conclusions have been found repeatedly. Black children, on the average, achieve lower IQ scores than white children. The second conclusion is that scores for black and white children overlap a great deal. Both of these results are shown in Figure 15. The third consistent finding is that the IQ scores of black children rise when their educational opportunities are improved. This fact, plus the knowledge that an enriched environment causes an increase in IQ, suggests that some, if not all, of the differences in measured IQ between black and white children may be explained by environmental factors.
Figure 15. Distribution of IQ scores for 386 white children and 103 black children of Kent County, Ontario, Canada
We know a great deal about who does well or poorly on IQ tests
A serious criticism of the data shown in Figure 15 can and should be made. It involves the specific content of items on IQ tests. Items were developed and standardized with white children whose backgrounds included similar experiences. Even rural white children tend to score below the norm. The techniques used in developing the tests, then, may explain many of the discrepancies between black and white children, and also between the different socioeconomic classes.
We are still trying to find out why
In an effort to deal with the fact that all people do not have the same background as white middle-class children, culture-fair tests have been suggested. The basic principle in these tests is to avoid items in which experiences in different cultural groups will affect the total score. There are two ways of approaching this problem. One is to use objects and events in the test items that almost everyone has had the same amount of experience with. The other approach is to balance items so that each group's experience is about equally sampled. Regardless of approach, however, efforts to construct culture-fair intelligence tests have not been too successful.
Psychologists clearly do not agree on the heredity vs. environment issue. There is even argument that Asian IQ's are higher than whites (Lynn, 1993). Following the The Bell shaped Curve book by Herrnstein and Murray (1994), there was considerable national commentary on the role of inheritance and cultural factors influencing IQ scores. As a result, the American Psychological Association asked a committee to review the literature and hopefully provide some clarification to this controversy. Neisser et al. (1996) published such a report whi