Historical review of WISC to WISC-IV

This article is an open access article and thus I am providing a link to a copy.

The article helps users understand the various changes that have occurred in this series, changes which may help explain IQ score differences in individuals who may have taken various versions over time.

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CHC theory and the Wechsler IQ scales and test development and interpretation

In 1998 Dr. Dawn Flanagan and I published the Intelligence Test Desk Reference book which was the first thorough treatment of CHC theory (then called Extended Gf-Gc theory). This book is now out-of-print.




We then took the concepts from the ITDR and, together with Dr. Sam Ortiz, presented a cross-battery approach to interpreting the Wechsler batteries.




And again, this book is no longer in print. This also means we no longer receive any $ for sales (conflict of interest disclosure). Table of contents for first three chapters below (click on images to enlarge)






The research, theory, and conceptual material in the second book is nearly identical to the first, but it was presented in the context of how to upgrade interpretation and understanding of the Wechsler batteries according to the CHC framework. Since then the same CHC overview material has been tweaked and updated in a series of CHC cross-battery books by Flanagan et al. But, the foundation of CHC theory, and how it can be integrated within a conceptual framework of test development and interpretation, is largely the same in these newer CHC cross-battery books.

Thus, given that these "mother and father" books are no longer in print, I took the liberty of copying the first three chapters of the Wechsler oriented book and am now making them available for my readers (click here). I make this material available to provide psychologists who have not done much reading regarding CHC theory an opportunity to have access to the basic foundation of CHC theory to help them see how it can be applied to the interpretation of an intelligence battery (in this case the Wechslers). By choosing the Wechsler material this also helps understand how the Wechsler batteries are evolving (either implicitly or explicitly--see Keith and Reynolds, 2010) when viewed from the lens of CHC theory.

But, one must recognize that this material is a bit dated. An update of CHC theory was later published in 2005 (click here to access...plus some other chapters), and was again updated this year by Schneider and McGrew (click here).

However, the CHC chapter I provide in this blog post, particularly when placed in the context of the Wechsler batteries, provides a solid foundation for understanding CHC theory and its impact on contemporary intelligence test development and interpretation. My goal is to increase awareness of CHC theory and its relevance to psychological assessment and interpretation. My goal is to spur others to become more current re: this now dominant framework in the field of applied IQ testing.


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1949 WISC: What date(s) should be used to calculate the Flynn effect for historical IQ scores?

What date should be used when calculating the effect of norm obsolescence (aka, Flynn Effect) for old 1949 WISC scores?

I have seen psychological reports for three different Atkins MR/ID death penalty case reports and one social security report that referenced old WISC scores. The WISC was published in 1949 and was used well into the mid 1970's (when replaced by the WISC-R in 1974). The Flynn Effect (click here for posts linking to Flynn Effect Series of reports) was not yet a documented phenomenon, so examiners using the test late it it's life cycle were often not aware of the potential for a massive Flynn effect. At the end of it's life cycle WISC results were often interpreted on the basis of norms that were 20-25 years out of date! This is the worst case scenario for the Flynn Effect I have seen in old psychological reports.

There is some debate on which date for any IQ test should be used to estimate the Flynn Effect. The date of publication or the median date of the years during which the norm data was collected. I believe the consensus is the later.

But, when one turns to the WISC manual, it makes no mention of the years spanned during the norming. Thus, I made a request for information to a number of professional listservs and a number of people directed me to Flynn's (2006) "Tethering the Elephant" article. There is a footnote in that table that provides a lead.

Note. All dates assigned to tests refer to the date at which the test was normed. This is what is relevant, of course, not the date when the test was published. Another date that practitioners might like to have is that for the norming of the WISC: from 1947 to 1948.

Alan Kaufman also communicated with me privately (personal communication, 9-23-11) regarding my question. He worked with David Wechsler on the the WISC-R. He said that during that time the date of 1947 was almost always mentioned during their work, but he never did see concrete proof.

Finally, a member of a neuropsych. listserv sent me a 1950 smoking gun journal article authored by staff from Psychological Corporation. The article was a more in-depth description of the WISC standardization. Although only mentioned briefly in one sentence on p. 102, the dates 1947-1948 are mentioned as the period of the data collection.

Thus, when faced with historical records with old WISC scores, especially those where the effect of norm obsolescence on the scores is dramatic, the best estimate to use for calculating the Flynn Effect is 1947 to 1948. I would tend to think that given the publication and production processes at the time that most of the data was collected during 1947 as many 1948 activities were likely involved in printing and production. But, to be safe, I would suggest examiners use both 1947 and 1948 and then round to the average estimate. One year typically does not make a huge difference.

Thanks to all who sent me tips and the article. The internet, and many professional listservs, are awesome sources of information.

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intelligence intelligence testing Atkins cases ICDP blog psychology school psychology neuropsychology forensic psychology criminal psychology criminal justice death penalty capital punishment ABA IQ tests IQ scores psychometrics adaptive behavior AAIDD mental retardation intellectual disability Flynn effect norm obsolescence WISC Wechsler IQ batteries

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