As a professional who has written about intelligence theories and tests and who is a coauthor of a frequently used individual measure of intelligence (WJ III), I often find other professionals and educators shocked when I highlight the less than perfect predictive capability of IQ tests. Although test manuals and research reports often report high correlations between IQ and achievement tests (e.g., .60-.70's), I occassionaly hear statements that suggest that some educators and assessment professionals fail to recognize that such high correlations (although some of the highest in all of psychology) are evidence of the fallibility of intelligence tests--they are less than perfect predictors.
Correlations of this magnitude tell us that IQ tests, on their best days, predict 40-50% of school achievement (Applied Psychometrics 101 – square the correlations and multiply by 100 to get the percent of variance explained). This is very good. Yet….50-60% of a person’s school achievement is still related to factors “beyond IQ!”
An unfortunate unintended negative side effect of the success of IQ tests can be the implicit or explict use of global IQ scores to form substandard or low expectations for individuals. How often have we all heard someone state, after hearing a child's general IQ score that, after using some norms or forumula to generate an "expected" achievement score, that teachers and parents should expect the child to achieve "at or below" these already below average expectations? It is often not recognized that for any given level of IQ score, half of the individuals with that score will achieve at or above predicted levels of expected achievement (based on that score). In the context of NCLB (No Child Left Behind), there is a real fear that IQ test scores may seduce educators and other education-related professionals into the “soft bigotry of low expectations” (it was either G. W. Bush or his then Education Secretary who coined this phrase).
The National Center on Educational Outcomes (NCEO) has recently published a report dealing specifically with this issue in the context of NCLB. Expectations for Students with Cognitive Disabilities: Is the Cup Half Empty or Half Full? Can the Cup Flow Over? (McGrew & Evans) is a report that addresses this issue. This report is pubished on the NCEO web page (click here). [If you go to the following page(click here) and right click on PDF (after the report title) you can download a pdf copy to your hard drive.] --- isn't technology wonderful?
As stated in the report introduction,
This report…includes an analysis of nationally representative cognitive and achievement data to illustrate the dangers in making blanket assumptions about appropriate achievement expectations for individuals based on their cognitive ability or diagnostic label. In addition, a review of research on the achievement patterns of students with cognitive disabilities and literature on the effects of teacher expectations is included. The literature raises numerous issues that are directly relevant to today’s educational context for students with disabilities in which both the Individuals with Disabilities Education Act (IDEA) and the No Child Left Behind (NCLB) Act of 2001 are requiring improved performance. Particularly for those students with cognitive disabilities, the information on expectancy effects should cause us much concern. Is it possible that expectancy effects have been holding students back in the past? Are we under the influence of silently shifting standards, especially for students with cognitive disabilities? It is anticipated that the information in this report will help guide decisions about appropriately high and realistic academic expectations for students with cognitive disabilities.
The fictitious story of Forrest Gumpis used in the report to illustrate the potential danger IQ score based generalized low expectations for students with disabilities---food for thought for educators, parents, and professionals involved in the education of students with disabilities during the current wave of NCLB-driven education reform.
After reading the report readers should feel compelled to yell “run Forrest run….from the potential negative impact of the soft bigotry of low expectations.”
3-14-05 note. Please note, in the spirit of full disclosure and potential conflicts of interest, that I was a coauthor of the NCEO report. I received $$ for writing the report but receive nothing for the number of copies that will be printed or distributed. Sorry for not pointing this out in the first post. I'm new at this....baby steps.