Engineering, other (35) Math/Comp (32) -O-2 g_(DAT-C - 45)>
Engineering, electrical (31)
FIGURE 8.4. Trivariate means for (A) favorite high school class and (B) least favorite class at age 18, (C) conferred bachelor's degree at age 23, and (D) occupation at age 33. Group ns are in parentheses. SAT-V = Verbal subtest of the Scholastic Assessment Test; SAT-M = Mathematical subtest of the Scholastic Assessment Test; and DAT-C = Composite of two subtests of the Differential Aptitude Test (space relations, SR + mechanical reasoning, MR). Panels A and B are standardized within sexes, panels C and D between sexes. The large arrowhead in panel C indicates that this group's relative weakness in spatial ability is actually twice as great as that indicated by the displayed length. From "Importance of Assessing Spatial Ability in Intellectually Talented Young Adolescents: A Longitudinal Study," by D. L. Shea, D. Lubinski, and C. P. Benbow, 2001, Journal of Educational Psychology, 93, pp. 607-610. Copyright 2001 by the American Psychological Association.
common; rather, their specific variance (illustrated in Figure 8.3) is responsible for distinguishing these groups psychologically.
Assessing Similar Constructs Through Different Modalities
Except for the example of orally administered health and worker literacy tests, the discussion thus far has focused on ability measures involving the same source. In this final section, a genuinely distinct method will be reviewed, the chronometric assessment of elementary cognitive processes (ECTs): memory, inspection time, and reaction time.
An intriguing history is associated with ECTs and the relationship between chronometric assessments thereof and intelligence. Although early on people like E. G. Boring recognized the potential significance of ECTs and intellectual appraisals (Peak & Boring, 1926), work in the area came to an abrupt halt following the publication of two dissertations, one supervised by James McKeen Cattell at Columbia (Wissler, 1901), the other supervised by E. B. Titchener at Cornell (Sharp, 1898-1899). This fascinating history is detailed in Deary (2000, pp. 70-81). In a nutshell, both of these investigations argued against the hypothesized relationship between ECTs and familiar indicators of intelligence. The two publications were widely cited as falsifying the idea that human intellectual behavior was associated with chronometric assessments of ECT (Deary, 2000). Yet, the studies were methodologically frail. Sharp's (1899) study, for example, used only seven postgraduate students. Wissler's (1901) study was more elaborate, but still only used high-ability subjects, and the simple reaction time measurements were based on only three to five trials. Furthermore, Wissler (1901) computed less than 10% of the possible correlations from his procedures and did not take errors of measurement into account. Thus, these two studies were not the strong "debunkers" most people have come to believe.
Modern experimentation has cast a different light on this modality as well. Over the past 20 years, experimentalists have come to appreciate that ECTs aggregate like psychometric items (Green, 1978). Aggregates of different kinds of basic cognitive processes have been constructed to form gen eral measures of conventional experimental phenomena (e.g., working memory, speed of cognitive processing), and these indicators have, in turn, been combined to reveal that their communality covaries highly with conventional measures of psychometric g. To be sure, there are experimental details to be worked out, because chronometric assessments of ECTs vary as a function of time of day, blood sugar level, medication, age, and a variety of individual differences variables (e.g., hormonal fluctuations). The work also requires vigilance of multiple experimental controls. Nonetheless, chronometric procedures are here to stay (Deary, 2000; Jensen, 2005; Lohman, 2000), because they appear to add incremental validity to conventional psychometric assessments (Luo et al., 2003, 2005). To say the least, they marshal an intriguing source of convergent validity on conventional psychometric assessments. Perhaps some day they will even effectively handle those annoying experiential contaminants associated with culture, learning, and opportunity that have always troubled appraisers of intellectual capabilities.
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