Harrington (1968a, 1968b), unlike such authors as Mercer (1979) and Helms (1992), emphasized the proportionate but small numbers of minority examinees in norming samples.
Their low representation, Harrington argued, made it impossible for minorities to exert any influence on the results of a test. Harrington devised an innovative experimental test of this proposal.
The researcher (Harrington, 1975, 1976) used six genetically distinct strains of rats to represent ethnicities. He then composed six populations, each with different proportions of the six rat strains. Next, Harrington constructed six intelligence tests resembling Hebb-Williams mazes. These mazes, similar to the Mazes subtest of the Wechsler scales, are commonly used as intelligence tests for rats. Harrington reasoned that tests normed on populations dominated by a given rat strain would yield higher mean scores for that strain.
Groups of rats that were most numerous in a test's norm-ing sample obtained the highest average score on that test. Harrington concluded from additional analyses of the data that a test developed and normed on a White majority could not have equivalent predictive validity for Blacks or any other minority group.
Reynolds, Lowe, et al. (1999) have argued that Harrington's generalizations break down in three respects. Harrington (1975, 1976) interpreted his findings in terms of predictive validity. Most studies have indicated that tests of intelligence and other aptitudes have equivalent predictive validity for racial groups under various circumstances and with many criterion measures.
A second problem noted by Reynolds, Lowe, et al. (1999) is that Chinese Americans, Japanese Americans, and Jewish Americans have little representation in the norming samples of most ability tests. According to Harrington's model, they should score low on these tests. However, they score at least as high as Whites on tests of intelligence and of some other aptitudes (Gross, 1967; Marjoribanks, 1972; Tyler, 1965; Willerman, 1979).
Finally, Harrington's (1975, 1976) approach can account for group differences in overall test scores but not for patterns of abilities reflected in varying subtest scores. For example, one ethnic group often scores higher than another on some subtests but lower on others. Harrington's model can explain only inequality that is uniform from subtest to subtest. The arguments of Reynolds, Lowe, et al. (1999) carry considerable weight, because (a) they are grounded directly in empirical results, rather than rational arguments such as those made by Harrington, and (b) those results have been found with humans; results found with nonhumans cannot be generalized to humans without additional evidence.
Harrington's (1975, 1976) conclusions were overgeneral-izations. Rats are simply so different from people that rat and human intelligence cannot be assumed to behave the same. Finally, Harrington used genetic populations in his studies.
However, the roles of genetic, environmental, and interactive effects in determining the scores of human ethnic groups are still topics of debate, and an interaction is the preferred explanation. Harrington begged the nature-nurture question, implicitly presupposing heavy genetic effects.
The focus of Harrington's (1975, 1976) work was reduced scores for minority examinees, an important avenue of investigation. Artifactually low scores on an intelligence test could lead to acts of race discrimination, such as misassignment to educational programs or spurious denial of employment. This issue is the one over which most court cases involving test bias have been contested (Reynolds, Lowe, et al., 1999).
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