To be fair, I do believe that there are a number of studies that show that the verbal and quantitative scales on the CogAT are good predictors of achievement in those domains and the nonverbal is less of a predictor of achievement. I'll edit to post links to some later.
Here's my hypothesis, though: I believe that the verbal and quantitative measures on the CogAT (the group ability test with which I am most familiar, b/c it is used extensively locally to me), are measuring exposure, knowledge, and achievement in those domains rather than ability in those domains. The non-verbal part, OTOH, which tends to be less considered by schools in determining giftedness, I believe measures visual spatial and abstract reasoning abilities more than achievement and also correlates less with achievement b/c it is more indicative of a divergent thinker not a child who can learn and regurgitate standard material easily. I'd tend to think that the non-verbal part of the CogAT is a better indication of giftedness as I define it which includes ability to create new knowledge and see connections and creative solutions more than repeat back knowledge that someone else has created.
Not really a study, but an author who tends to agree:
Increasing Minority Children’s Participation in Gifted Classes Using the NNAT: A Response to Lohman (
http://gcq.sagepub.com/content/49/1/29.short) - keep in mind that this guy is the author of the NNAT as Lohman, who wrote the original critique of the NNAT as compared to the CogAT (above) is the author of the CogAT.
In a previous article, we (Naglieri & Ford, 2003) provided evidence from a large-scale study that similar proportions of White, Black, and Hispanic children would be identified as gifted using the Naglieri Nonverbal Ability Test (NNAT; Naglieri, 1997). Lohman (2005) has taken issue with our conclusions and our methods. We provide several responses to his arguments and make five important points. First, we take the position that underrepresentation of minority children in classes for the gifted is a serious problem that must be remedied. Second, traditional measures of ability that include verbal and quantitative tests pose particular problems to less-advantaged children who may be intelligent, but lack verbal and math knowledge. Third, we argue that the CogAT verbal and quantitative tests of “ability” correlate higher with the ITBS “achievement” tests than the CogAT nonverbal tests of ability because of the similarity of skills needed to answer the items on both the ITBS and the CogAT. Fourth, we reject an emphasis on “academically gifted” children that excludes the identification of “intellectually gifted” children who happen to have poor academic skills. Fifth, we request that critics of the NNAT provide evidence of the magnitude of race and ethnic differences, as well as the likely effect on representation of minorities using whatever alternatives they propose.
This gets interesting here b/c Lohman, the author of the CogAT, has written extensively on his belief that ability and achievement are not separate constructs. I have to admit that I tend to disagree in that I've seen high ability people who are not high achievers and the reverse. I wonder if his thought process leads toward beliefs more in line with the current "talent development" model that the NAGC, for instance, embraces which requires high achievement and motivation to be considered "gifted."
For instance, here's a newsletter on the CogAT in which Lohman writes,
Ability tests are perhaps best understood as achievement tests of a special sort. Conversely, achievement tests may be seen as ability tests of a special sort.
and
The individual believes that ability tests measure (or ought to measure) innate potential. This means that culture, education, personal experience, and motivation should not influence scores. Similarly, achievement tests measure (or ought to measure) only knowledge and skills learned in school...
All abilities—from those required by the simplest reaction-time task to the most complex problem-solving task—respond to practice and training...
all abilities are developed...
If all abilities are achievements and all thinking is rooted in knowledge, then it makes little sense to talk about abilities and achievements as if they were qualitatively different (Snow, 1980). Rather, many who study individual differences see a single space of developed competencies or abilities (Humphreys, 1981; Cronbach, 1990; Carroll, 1993; Horn & Noll, 1997). Some
develop primarily through formal schooling, others through out-of-school experiences common to most children in a given culture, and still others through experiences that are unique to the individual.
I do agree with him in some areas, for instance,
Research on academic learning shows that the best predictors of subsequent learning in a domain are (1) current achievement in that subject area, (2) the ability to reason in the symbol systems of that domain, (3) interest in that subject area, and (4) the willingness to persist in order to attain excellence
however I am not ready to say that we just call high achievement and high intelligence the same thing.
Thoughts?
eta: to drag another person into this, I was at the Mensa World Gathering years ago and attending a talk by Deborah Ruf about interpreting IQ tests. One of the audience members asked her about improving one's intelligence or IQ through practice or training. Her response (I'm not quoting, just paraphrasing what I recall) was that you can increase your IQ test score by practicing the tasks on the test, but not your actual IQ or intelligence.
These seem to be totally divergent beliefs on intelligence, no?
