Monday, December 14, 2009

AAIDD intellectual disability manual (11th edition): Intelligence component -1 standard deviation below average? Part 1 of series of posts.

“For purposes of diagnosis, intellectual functioning is currently best conceptualized and captured by a general factor of intelligence.  Intelligence is a general mental ability.  It includes reasoning, planning, solving problems, thinking abstractly, comprehending simple ideas, learning quickly, and learning from experience.  The “significant limitations in intellectual functioning” criterion for a diagnosis of intellectual disability is an IQ score that is approximately two standard deviations below the mean, considering the standard error of measurement for the specific instruments used and the instruments strengths and limitations.”  (AAIDD, 2010, p. 31)
[Note - this is a cross-blog post originally posted to IQs Corner sister blog (ICDP) yesterday.]

It has been nearly 50 years since the first official American Association on Intellectual and Developmental Disabilities (AIDD; previously AAMR  and AAMD) manual (1961) for defining intellectual disability (ID: previously mentally retarded-MR; Greenspan & Switzky, 2006a) and the latest version (11th edition; aka the “green book”) was published (AAIDD, 2010).  The ongoing refinement of the ID manual has taken many twists and turns, often producing internal debates within the ID community (see Greenspan & Switzky, 2006b; Greenspan, 1997, 2006).  Despite the debates, the ongoing evolution of each successive manual has been guided by the goal to describe “best practices” for defining, classifying, and providing services for individuals with ID.  The green book continues this tradition.  One wonders whether the latest iteration of the official AAIDD manual will resolve many of the ongoing questions and debates (see Switzky & Greenspan, 2006a) or, whether it will generate new controversies and fissures in the profession regarding the definition and classification of ID. 

With great anticipation, I recently received my copy of the AAIDD green book.  Although my research interests have spanned (at different times in my career) both theoretical and assessment issues in the domains of personal competence, adaptive behavior, and intelligence, my most recent research and writings have focused primarily on intelligence theory and testing.  Thus, I immediately turned to Chapter 4 of the manual (Intellectual Functioning and Its Assessment).  Questions in my mind where:  Is it up-to-date?  Did it incorporate state-of-the-art research on the evolving taxonomy of human cognitive abilities?  Did it provide guidance to practitioners regarding critical intelligence testing issues? 

The existence of this blog post (to introduce a series of future blog posts) reflects my obvious answers to the above questions.  To be frank, Chapter 4 is a disappointment (of a magnitude of at least -1 standard deviation below expectations).  I’ve waited two months since first reading the chapter before drafting this introductory post.  I needed time to reflect on whether my initial knee-jerk reactions were accurate or possibly related to potential conflicts of interest (see “full disclosure” note at end of this post).  I also needed to decide if I had the fortitude to take a controversial public stance regarding the AAIDD chapter on intellectual functioning.  With each passing week my decision was made easier as I read more-and-more psychometrically and professionally flawed Atkins MR/ID death penalty court decisions (many of these decisions, along with some of my comments, can be found at the current blog  I finally decided I had a professional responsibility to share my analysis and comments.

I believe, given the adversarial nature of Atkins court proceedings (see Greenspan & Switzky, 2006c), that certain lawyers and courts might use (or misinterpret) the contents of Chapter 4 (particularly the focus on "general intelligence" and thus, a single full scale IQ score and resultant "bright line" cutoff criteria) to circumvent the rights of individuals with ID to fair, equitable treatment and equal protection under the law.   And as others have noted, these are literally life-or-death issues.  Thus, I’ve decided to publically post my comments, criticisms and questions in hopes of stimulating debate and dialogue.  I will personally invite  members of the AAIDD Ad Hoc Committee on Terminology and Classification to provide guest response posts to my criticisms if they feel so compelled (which I will post “as is” as guest posts to the ICDP blog). 

Before sharing my concerns regarding Chapter 4, I acknowledge and recognize the hard work of the dedicated AAIDD Ad Hoc committee members.  Reaching professional committee-based consensus on the definition and classification of ID has always been a challenge (“A committee is a cul-de-sac down which ideas are lured and then quietly strangled,” Sir Barnett Cocks, in New Scientist, 1973). The committee members obviously spent considerable time and effort grappling with complex and conflicting issues.  I recognize that by nature, multiple member and viewpoint committee’s are constraint-driven consensus mechanisms.  Such constraints (political, economic, resources, ethical, possible conflicts of interest, etc.) will obviously not allow for the production of the “perfect” manual.  By definition, constraint-driven design typically results in “satisficing” (adequate and satisfactory) outcomes—not perfect outcomes (Simon, 2003).

Also, it would be professionally inappropriate if I only mentioned criticisms to select sections of Chapter 4.  On the positive side of the ledger I am pleased Chapter 4 addresses a number of important intelligence testing issues such as measurement error (SEM), test fairness, the Flynn Effect, comparability of scores from different IQ tests, practice effects, extreme scores, examiner credentials, and the ever complex and controversial use of cutoff scores.

Chapter 4 of the manual spans slightly more than 11 pages and covers the operational definition of intelligence (single general ability vs multiple intelligences), limitations in the operational definition, and challenges and guidelines regarding the use of IQ scores.  Obviously there will be some negative reactions given the breadth of topics covered in a mere 11+ pages (page length was probably one of the design constraints).  Despite this acknowledged constraint, my professional evaluation of the intellectual functioning component chapter finds it seriously wanting in four primary areas:
  1. A failure to reflect state-of-the-art intelligence theory and assessment research
  2. A misunderstanding and inaccurate description of the major intelligence theories
  3. An apparent lack of scientific rigor in the section on the nature and definition of intelligence as evidenced by little in the way of substantive revision of the content (and minimal reference updating or “refreshing”) from the 2002 manual to the same section in the 2010 manual—resulting in the failure to incorporate significant advances and the emerging consensus regarding the nature of psychometrically-based intelligence theories, theories that have historically provided the foundation for technically sound intelligence batteries used in ID diagnosis and classification
  4. The elimination of the 2002 section that reviewed commonly available intelligence test batteries. 

These four areas will be the foundation of my future posts in this series, which in turn may spin off additional specific or splinter issue-based posts and recommendations.

In conclusion, as written, I believe that the AAIDD operational definition of intelligence has the potential to misinform professionals working in the field of ID.  More importantly, given that the AAIDD manual is no longer only a guide for professionals and agencies working in clinical settings, but each word, sentence and paragraph of the manual are now parsed in adversarial Atkins ID death penalty deliberations (Greenspan & Switzky, 2006c), the deficiencies in the AAIDD operational definition of intelligence has potentially very serious ramifications.

I know that I am often a naïve idealist.  Ideally I hope that my forthcoming critical comments, combined with a spirited back-and-forth dialogue, will produce productive scholarly discourse, discourse that may result in AAIDD upgrading/revising their current written statement regarding the first prong of an ID diagnosis—intellectual functioning (Chapter 4) via new position papers or journal articles, web-based clarifications, and/or the publication of more specific professional guidelines.

Stay tuned.  Hopefully my first critique post will be completed within a week.

  • American Association on Intellectual and Developmental Disabilities (2010).  Intellectual Disability:  Definition, classification, and systems of supports.  Washington, DC.  Author
  • Greenspan, S. (1997).  Dead manual walking?  Why the 1992 AAMR definition needs redoing.  Education and Training in Mental Retardation and Developmental Disabilities, 32, 179-190.
  • Greenspan, S. (2006).  Mental retardation in the real world:  Why the AAMR definition is not there yet.  In S. Greenspan and H. Switzky, (Eds.), What is mental retardation?  Ideas for an evolving disability in the 21st Century.  Washington, DC:  American Association on Mental Retardation.
  • Greenspan, S. & Switzky, H. (2006a).  Forty-four years of AAMR manuals.  In S. Greenspan and H. Switzky, (Eds.), What is mental retardation?  Ideas for an evolving disability in the 21st Century.  Washington, DC:  American Association on Mental Retardation.
  • Greenspan, S. & Switzky, H. (2006b).  What is mental retardation?  Ideas for an evolving disability in the 21st Century.  Washington, DC:  American Association on Mental Retardation.
  • Greenspan, S. & Sitzky, H. (2006c).  Lessons from the Atkins decision for the next AAMR manual.  In S. Greenspan and H. Switzky, (Eds.), What is mental retardation?  Ideas for an evolving disability in the 21st Century.  Washington, DC:  American Association on Mental Retardation.
  • Simon, H.A. (2003).  Nobel Prize in Economic Sciences, 1978.  American Psychologist, 58 (9), 753-755. 
Full disclosure statement:  I, Kevin McGrew, am a coauthor of the Woodcock-Johnson III Battery, a battery that includes an intelligence (IQ) component that is often used in the assessment and classification of individuals with ID.  Thus, I have a potential monetary conflict of interest regarding policies and guidelines related to the use of intelligence tests.  Furthermore, all  comments in this blog post, and future blog posts, reflect my individual professional opinion and do not necessarily reflect the opinions of the WJ III author team or the publisher of the WJ III (Riverside Publishing).

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