Combining multiple intelligence test scores (IQs) into a grand psychometrically sound estimate. Joel Schneider’s free on-line web app.

In an earlier post in March, I alerted readers to a new journal publication that presented a psychometrically sound rational and method for combining multiple intelligence test scores into a single grand estimate.  Below is the formal APA reference:  Go to link above for more info.

Schneider, W. J., Reynolds, C. R., McGrew, K. S., & Salekin, K. L. (2026). Life-and-death psychometrics: Generalizable best methods for combining scores in intellectual disability and other diagnostic assessments. Journal of Pediatric Neuropsychology, 12(2), 47–65.

I’m pleased to report that Dr. Joel Schneider has developed a free on-line web app that allows users to implement the recommended method.  Thanks to Joel.

Click on image to enlarge for easy reading

Breaking legal and research news: SCOTUS (US Supreme Court) decision re multiple IQ scores in intellectual disability (ID) death penalty case (Hamm v Smith) - A DIG decision upholding the lower court decision

Today SCOTUS ruled on the Hamm v Smith multiple IQ score Atkins intellectual disability (ID) case that was argued before SCOTUS last December. This important decision, with all concurring and dissenting opinions, is available here.  Interested parties should read all the opinions. 

All documents and the history of the case can be found in a prior IQs Corner post.  As noted in the prior lengthy post, APA submitted an Amicus brief that, based on the reading of some of the justices opinions, suggests it (together with a AAIDD Amicus Brief) played an important role in the decision.

Briefly, when SCOTUS dismisses the writ of certiorari as improvidently granted it means the justices recognized that they made a mistake in agreeing to hear the case and decided to dismiss it without issuing a ruling on the merits. In legal shorthand, this is often referred to as a "DIG" (Dismissed as Improvidently Granted). This typically happens after the Court has accepted the case, reviewed the briefs, and sometimes even heard oral arguments. 

In practice, this means that the lower court decision—which is consistent with APA’s Amicus brief—that argued that multiple IQ scores should be viewed holistically  augmented by clinical judgement—stands. This means Mr. Smith will not be executed and, more importantly, the ruling does not upset the status of prior Atkins case law.  Given the recent direction and flavor of SCOTUS, there was a fear that SCOTUS might render a formal decision that would set back prior SCOTUS Atkins ID decisions.  So, this is a win for maintaining the principles of clinical judgement, the opinions and standards established by the established medical communities (both APA’s, AAIDD), and the need for a holistic approach to the interpretation of multiple IQ scores together with adaptive behavior.

A reading of the concurring opinions indicates that APA’s brief, as well as several key APA and AAIDD ID-related publications referenced in their decisions, were influential in the decision.  Several of the dissenting opinions reveal some troubling thinking by several justices. 

As a potential conflict of interest (COI) notice, I (Dr. Kevin McGrew), together with Dr. Joel Schneider and Dr. Cecil Reynolds (as noted on page three the APA amicus brief), were consultants to APA in the drafting of that brief.

It should be noted that as a result of the work of APA Amicus brief working committee, a peer-reviewed paper outlining a psychometrically sound approach (developed by Dr. Joel Schneider) for integrating multiple IQ scores was started during the deliberations and was recently published (Schneider, Reynolds, McGrew & Salekin, 2026) after the oral argument's.  This issue will likely to be revisited in future state cases, with Schneider et al. (2026) now elevated to a scientifically sound multiple IQ composite score method.

AI Brief: Is the Intellectual Functioning Component of AAIDD’s 12th Manual Satisficing?

AI Brief:  Is the Intellectual Functioning Component of AAIDD's 12th Manual Satisficing?

 (McGrew, 2021)

 

Dr. Kevin McGrew with assist from Google NotebookLM

 

In a commentary published in Intellectual and Developmental Disabilities, Kevin S. McGrew  evaluated the intellectual functioning section (prong 1) of the AAIDD’s 12th edition manual (2021) for diagnosing intellectual disabilities (ID). He commends the organization for finally adopting the Cattell-Horn-Carroll (CHC) theory, which aligns the manual with modern scientific consensus on cognitive abilities. However, the author expresses significant concern about the manual’s contradictory guidance on part scores, arguing that its ambiguous stance could lead to legal and diagnostic confusion. McGrew also highlights various technical measurement issues and numerous copyediting errors that he believes undermine the manual's status as an authoritative resource. He suggests that while the manual is satisfactory in its theoretical shift, it does not provide the precise clarity needed for high-stakes clinical and judicial settings.

 

_______________________

 

In his review of the 12th edition of the American Association on Intellectual and Developmental Disabilities (AAIDD) manual, McGrew (2021; link for downloading article) evaluates whether the "Intellectual Functioning Component" (aka.,prong 1 of a three-prong definition of intellectual disability—ID) provides a "satisficing"—or satisfactory and sufficient—solution for practitioners and scholars.[1] McGrew draws on over 45 years of experience in school psychology and intelligence research, theory, and test development. In addition, he draws on his expert work and consultation (since 2009) on Atkins intellectual disability (ID) death penalty cases in legal settings. McGrew provides an evaluation of the AAIDD’s manual's prong 1 (intellectual functioning) theoretical grounding, technical guidance, and professional polish. He does not evaluate the other two ID prongs (adaptive behavior and age of onset).

Advancement in Intelligence Theory

McGrew awards the manual a Grade B+ for its formal adoption of the Cattell-Horn-Carroll (CHC) theory of intelligence. This shift aligns the AAIDD manual with the contemporary consensus taxonomy of cognitive abilities, moving away from outdated models. However, McGrew notes that the manual "muddies the CHC waters" by giving preferential treatment to fluid (Gf) and crystallized (Gc) intelligence while neglecting other broad CHC abilities like learning efficiency (Gl), working memory (Gwm), retrieval fluency (Gr), auditory processing (Ga), visual-spatial processing (Gv), and processing speed (Gs). He suggests that a visual-graphic model of the CHC hierarchical model would have been a beneficial addition for users.

Measurement and Organizational Challenges

The manual receives a Grade B- for its treatment of major measurement issues. While it provides adequate coverage of such measurement issues as the standard error of measurement (SEM), confidence intervals, and the Flynn effect (aka., norm obsolescence), McGrew criticizes the lack of a topic index, which makes finding specific guidance very frustrating. For instance, practice effects are obscurely placed under "progressive error" in the glossary, and the Flynn effect is curiously categorized under "Making a Retrospective Diagnosis," despite being relevant to historical and current intellectual assessments.

The Part-Score Controversy

The most critical evaluation—a Grade C—is reserved for the manual's handling of part scores. McGrew identifies three primary failures in this area:

 

●      Inconsistency: The manual contradicts itself by advising against the use of part scores as proxies for general intelligence (psychometric g) while simultaneously suggesting that their valid use requires 3–6 subtests of Gf and Gc.

●      Variance with Other Authorities: This "just say no to part scores" stance conflicts with other major authoritative sources, such as the DSM-5, which acknowledges that highly discrepant subtest scores may invalidate an overall IQ score.

●      Scientific and Legal Tensions: McGrew argues that the manual fails to address the "General-2-individual" (G2i) legal principle which acknowledges that group-based scientific research (e.g., suggesting full-scale scores are always superior) may not apply to every unique individual case—the G2i principle conundrum is that scientists generalize; but courts must particularize to an individual. He warns that without clearer guidance; legal entities may fill the void with "remedies of dubious quality.”

Editorial Quality and Professionalism

McGrew gives the manual a Grade D for style and substance, citing at least 20 copyedit errors in the sections relevant to the intellectual functioning prong alone. These include misspellings of prominent researchers, incorrect terminology like "test e-norms," and frequent "misplaced italics.” He contends that such preventable errors tarnish the manual’s status as an "authoritative" and "definitive" source for diagnosing intellectual disabilities.

Conclusion

McGrew concludes that while the endorsement of CHC theory is a significant positive revision, the manual’s obfuscation regarding part scores and its numerous editorial flaws represent major missed opportunities. He emphasizes that practitioners cannot wait another decade for the next edition to offer more robust guidance, particularly in high-stakes legal and diagnostic settings. He concludes that while he may be a "tough grader," his critiques are intended to push AAIDD toward more robust and clearer guidance in future editions or supplements

[1] Nobel laureate Herb Simon advanced the behavioral economics concept of satisficing (Simon, 1956)—the idea that, although we may aspire to optimal solutions, real-world constraints often require us to settle on what is both satisfactory and sufficient (hence, the portmanteau term satisficing).

Research alert: Life-and-death psychometrics: Generalizable best methods for combing scores in intellectual disability and other diagnostic assessments - #pschometrics #Atkins #SCOTUS #IQ #intelligence #ID #intellectualdisability #AAIDD

Click on image to enlarge for better viewing 

Click here for the Journal of Pediatric Neuropsychology article page.

Abstract

A diagnosis of intellectual disability is a momentous event that can determine eligibility for special services and supportive sources of income, and in the criminal arena, it can be a matter of life and death. For criminal defendants who might otherwise face capital punishment, it is a matter of life and death. Individuals evaluated for intellectual disability often have been given multiple intelligence tests, sometimes with results falling on both sides of the diagnostic threshold. In all cases, the diagnostic decision must be based on a rigorous examination of the totality of evidence in the context of systematic clinical judgment. When multiple IQ results are relevant and comparable, they can be combined into a properly computed composite score to assist the clinician charged with diagnostic responsibility in determining if Prong 1, deficits in intellectual functioning, of the three-prong criteria necessary for an intellectual disability diagnosis has been met. Best psychometrically grounded methods for these calculations are presented along with a discussion of inappropriate approaches for accurately combining multiple scores. To make these methods accessible to professionals outside the discipline of psychology, all calculations are fully explained in the context of foundational concepts. 

IQs Corner. In what way are #intelligence testing (#IQ) and the US Supreme Court (#SCOTUS) alike?—SCOTUS will be hearing important case addressing #multiple IQ scores and #intellectualdisability #Dx in fall 2025 term

This fall 2025, the Supreme Court of the United States (SCOTUS) will be hearing a case related to intelligence testing in the context of Atkins intellectual disability (ID) death penalty cases. The case is Hamm v Smith.

The question before SCOTUS is :  Whether and how courts may consider the cumulative effect of multiple IQ scores in assessing Atkins claims (in the context of diagnosis ID in death penalty cases)?

Note.  In order to save space and time, instead of writing “general intelligence” or “general intellectual functioning” every time, I use the abbreviation “IQ”.

The respondent (Joseph Smith) has five IQ test scores from comprehensive IQ tests.  He obtained two scores of 75 and 74 during the developmental period (before age 22), and three scores of 72, 78, and 74 between the ages of 28 and 46.  

This case is important for assessment professionals who conduct intelligence testing in general, and potential ID diagnostic cases (Atkins cases in particular).  I find this SCOTUS case particularly interesting given that in 2021, after the 2021 release of the latest official AAIDD manual (Intellectual disability: Definition, diagnosis, classification, and systems of supports), I published a critique where I specifically stated, as one weakness of the new AAIDD manual that “…many high-stakes ID cases often include case files that include multiple IQ scores across time or from different IQ tests. Some form of guidance, at minimum in a passing reference, to the issues of the convergence of indicators and IQ score exchangeability would have been useful. Users will need to go beyond the AAIDD manual for guidance (see Floyd et al., 2021; McGrew, 2015; and Watson, 2015)” (click here to download and read this critique).

All official petitioner and respondent legal briefs (and amicus briefs) have now been published at the SCOTUS blog as of yesterday.  The number of documents posted on the SCOTUS docket are many.  To help the reader better determine which documents are most critical (the final briefs), instead of clicking away on the various links at the SCOUTUS blog, I’ve organized the petitioner and respondent brief links below.

If you prefer to not wade through all the briefs (it is not for everyone), I would encourage practicing assessment professionals read the three respondent-related briefs.  The points made are relevant to all who conduct intellectual assessments.  As a potential conflict of interest notice, I (Dr. Kevin McGrew), together with Dr. Joel Schneider and Dr. Cecil Reynolds (as noted on page three for the APA amicus brief), were consultants to APA in the drafting of that brief.  This work was performed pro bono. I, at a minimum, suggest reading all the respondent briefs.  If time permits, I would also suggest reading the petitioner’s Alabama brief and the US Justice Department Solicitor General’s brief to better understand the petitioner and respondent positions re Hamm v Smith. 

Petitioner briefs

• The state of Alabama brief.  Alabama is the petitioner.  That is, if you want to read why the State of Alabama asked SCOTUS to hear this case, click on the link provided.
• The Alabama brief also includes a very long appendix for those who want to read the prior courts related testimony from the state and various experts. This is a very long read and is not necessary for readers who only want to understand the legal and professional issues. 
• Supporting amicus brief from the US Justice Department Solicitor General.
• Two supporting briefs from legal groups—the American Legal Foundation and the Criminal Justice Legal Foundation.
• Supporting amicus briefs from other states (Idaho et al.; Kentucky)

Respondent briefs

• Smiths respondent brief.
• Supporting amicus brief from American Psychological Association (APA), American Psychiatric Assocation (ApA), and Alabama APA.
• Supporting amicus brief from AAIDD et al.

Final comment.  Those from school psychology should make note that we three consultants involved in drafting the APA/ApA,AL-APA brief all had our original educational roots in the profession of school psychology.  Furthermore, SP professionals should note the significant number of authoritative references to publications authored by school psychologists in the respondents briefs, as well as in some of the petitioners briefs.  I’ve been doing expert consultation, writing declarations, and testifying in court re: Atkins ID cases since 2009.  Joel Schneider and Cecil Reynolds have also been active in a similar capacity.  There are more psychologists who come from, or are affiliated with, the field of school psychology who have been prominent consultants/experts to lawyers and the courts re Atkins cases.  

Perhaps some of these briefs should be assigned readings (in intellectual assessment courses or special topic seminars) for graduate students being trained in the art and science of intelligence testing and interpretation.

Research Byte: Understanding #Adaptive Skills in #Borderline #IntellectualFunctioning: A Systematic #Review - #schoolpsychology #DD #intelligence #developmentaldisabilities #SPED

 Click on image to enlarge for easy reading

Understanding Adaptive Skills in Borderline Intellectual Functioning: A Systematic Review

Open access copy available by clicking here.

Abstract

Borderline intellectual functioning (BIF) is characterized by an IQ typically ranging from 70 to 85, combined with deficits in adaptive functioning. Despite its prevalence, individuals with BIF are often excluded from diagnostic and support systems, which traditionally focus on strictly defined intellectual disabilities. This article presents a systematic review conducted across the ProQuest, WoS, SCOPUS, and EBSCOhost databases, aiming to develop a profile of the adaptive functioning in individuals with BIF. A total of 64 documents published from 2012 to the present were included, all of them addressing BIF and adaptive functioning skills, and quality was assessed using the SSAHS tool. The findings presented are synthesized according to conceptual, social, and practical domains and reveal that individuals with BIF experience widespread difficulties across the conceptual, social, and practical domains. Additionally, societal barriers, primarily limiting access to support services, persist. However, there are emerging resources aimed at supporting this population, such as legislative efforts to facilitate their integration into the labor market. The implications and limitations of the findings are discussed, highlighting the need to consider the adaptive functioning skills of individuals with BIF. 

Research Byte: #Cognitive augmentation: #AI enhanced tools for supporting individuals with cognitive #disabilities - #schoolpsychology #SPED #cognitive

 Click on image to enlarge for easy reading

Journal web page found here.

#AAIDD's #IQ Part-Score Position (with reference to diagnosing #intellectual #disabiity [#ID]) Is at Variance With Other Authoritative Sources—Important for #schoolpsychologists

In a 2021 commentary regarding the most recent official AAIDD intellectual disability definition and classification manual (2021), I raised a concern regarding AAIDD’s position that only a full scale or global IQ score can be used for a Dx of ID.  No room was left for clinical judgement for n=1 unique cases.  Click here to download and read the complete article.  Below is some select text.

“AAIDD's [IQ] Part-Score Position Is at Variance With Other Authoritative Sources”

In AAIDD’s The Death Penalty and Intellectual Disability (Polloway, 2015), both McGrew (2015) and Watson (2015) suggest that [IQ] part scores can be used in special cases. (Note that these two chapters, although published in an AAIDD book, do not necessarily represent the official position of AAIDD.) The limited use of part scores is also described in the 2002 National Research Council book on ID and social security eligibility (see McGrew, 2015; Watson, 2015). The authoritative Diagnostic and Statistical Manual of Mental Disorder—Fifth Edition (DSM-5) manual implies that part scores may be necessary when it states that ‘‘highly discrepant subtest scores may make an overall IQ score invalid'' (American Psychiatric Association, 2013, p. 37). Finally, in the recent APA Handbook of Intellectual and Developmental Disabilities (Glidden, 2021), Floyd et al. (2021) state ‘‘in rare situations in which the repercussions of a false negative diagnostic decision would have undue or irreparable negative impact upon the client, a highly g-loaded part score (see McGrew, 2015a) might be selected to represent intellectual functioning'' (emphasis added; p. 412).

“ In a unique n = 1 high-stakes setting, a psychologist may be ethically obligated to proffer an expert opinion whether the full-scale score is (or is not) the best indicator of general intelligence. There must be room for the judicious use of clinical judgment-based part scores. AAIDD's purple manual complicates rather than elucidates guidance for psychologists and the courts. In high-stakes settings, a psychologist may be hard pressed to explain that their proffered expert opinions are grounded in the AAIDD purple manual, but then explain why they disagree with the ‘‘just say no to part scores'' AAIDD position.”

The use of the Woodcock-Johnson Fourth Edition (WJ IV) GIA Cognitive IQ score in intellectual disability (ID) determination

The WJ IV Cognitive GIA in iintellectual disability (ID) assessment from Kevin McGrew

Law Review Article: Evaluating Intellectual Disability: Clinical Assessments in Atkins Cases (Ellis et al., 2018)

This new law review article is, IMHO, the best overview article regarding the history of ID, the legal issues in Atkins cases, and good discussion of the major conceptual and measurement issues found in many Atkins cases. An excellent introduction to ID issues in Atkins cases.

EVALUATING INTELLECTUAL DISABILITY: CLINICAL ASSESSMENTS IN ATKINS CASES

James W. Ellis, Caroline Everington, Ann M. Delpha

ABSTRACT

The intersection of intellectual disability and the death penalty is now clearly established. Both under the U.S. Supreme Court's constitutional decisions and under the terms of many state statutes, individual defendants who have that disability cannot be sentenced to death or executed. It now falls to trial, appellate, and post-conviction courts to determine which individual criminal defendants are entitled to the law's protection. This Article attempts to assist judges in performing that task. After a brief discussion of the Supreme Court's decisions in Atkins v. Virginia, Hall v. Florida, and Moore v. Texas, it analyzes the component parts and terminology of the clinical definition of intellectual disability. It then offers more detailed discussion of a number of the clinical issues that arise frequently in adjudicating these cases. For each of these issues, the Article's text and the accompanying notes attempt to provide judges with a thorough survey of the relevant clinical literature, and an explanation of the terminology used by clinical professionals. Our purpose is to help those judges to become more knowledgeable consumers of the clinical reports and expert testimony presented to them in individual cases, and to help them reach decisions that are consistent with what the clinical literature reveals about the nature of intellectual disability and best professional practices in the diagnostic process.

Click on images to enlarge







- Posted using BlogPress from my iPad

The Relation between Intelligence and Adaptive Behavior: A Meta-Analysis

Very important meta-analysis of AB IQ relation. Primary finding on target with prior informal synthesis by McGrew (2015)

The Relation between Intelligence and Adaptive Behavior: A Meta-Analysis   
 
Ryan M. Alexander 
 
ABSTRACT 
 
Intelligence tests and adaptive behavior scales measure vital aspects of the multidimensional nature of human functioning. Assessment of each is a required component in the diagnosis or identification of intellectual disability, and both are frequently used conjointly in the assessment and identification of other developmental disabilities. The present study investigated the population correlation between intelligence and adaptive behavior using psychometric meta-analysis. The main analysis included 148 samples with 16,468 participants overall. Following correction for sampling error, measurement error, and range departure, analysis resulted in an estimated population correlation of ρ = .51. Moderator analyses indicated that the relation between intelligence and adaptive behavior tended to decrease as IQ increased, was strongest for very young children, and varied by disability type, adaptive measure respondent, and IQ measure used. Additionally, curvilinear regression analysis of adaptive behavior composite scores onto full scale IQ scores from datasets used to report the correlation between the Wechsler Intelligence Scales for Children- Fifth edition and Vineland-II scores in the WISC-V manuals indicated a curvilinear relation—adaptive behavior scores had little relation with IQ scores below 50 (WISC-V scores do not go below 45), from which there was positive relation up until an IQ of approximately 100, at which point and beyond the relation flattened out. Practical implications of varying correlation magnitudes between intelligence and adaptive behavior are discussed (viz., how the size of the correlation affects eligibility rates for intellectual disability).
 
Other Key Findings Reported
 
McGrew (2012) augmented Harrison's data-set and conducted an informal analysis including a total of 60 correlations, describing the distributional characteristics observed in the literature regarding the relation. He concluded that a reasonable estimate of the correlation is approximately .50, but made no attempt to explore factors potentially influencing the strength of the relation.
 
Results from the present study corroborate the conclusions of Harrison (1987) and McGrew (2012) that the IQ/adaptive behavior relation is moderate, indicating distinct yet related constructs. The results showed indeed that the correlation is likely to be stronger at lower IQ levels—a trend that spans the entire ID range, not just the severe range. The estimated true mean population is .51, and study artifacts such as sampling error, measurement error, and range departure resulted in somewhat attenuated findings in individual studies (a difference of about .05 between observed and estimated true correlations overall).
 
 
The present study found the estimated true population mean correlation to be .51, meaning that adaptive behavior and intelligence share 26% common variance. In practical terms, this magnitude of relation suggests that an individual's IQ score and adaptive behavior composite score will not always be commensurate and will frequently diverge, and not by a trivial amount. Using the formula Ŷ = Ȳ + ρ (X - X ̅ ), where Ŷ is the predicted adaptive behavior composite score, Ȳ  is the mean adaptive behavior score in the population, ρ  is the correlation between adaptive behavior and intelligence, X is the observed IQ score for an individual, and X ̅ is the mean IQ score, and accounting for regression to the mean, the predicted adaptive behavior composite score corresponding to an IQ score of 70, given a correlation of .51, would be 85 —a score that is a full standard deviation above an adaptive behavior composite score of 70, the cut score recommended by some entities to meet ID eligibility requirements. With a correlation of .51, and accounting for regression to the mean, an IQ score of 41 would be needed in order to have a predicted adaptive behavior composite score of 70. Considering that approximately 85% of individuals with ID have reported IQ scores between 55 and 70±5 (Heflinger et al., 1987; Reschly, 1981), the eligibility implications, especially for those with less severe intellectual impairment, are alarming. In fact, derived from calculations by Lohman and Korb (2006), only 17% of individuals obtaining an IQ score of 70 or below would be expected to also obtain an adaptive behavior composite score of 70 or below when the correlation between the two is .50. 
 
 
The purpose of this study was to investigate the relation between IQ and adaptive behavior and variables moderating the relation using psychometric meta-analysis. The findings contributed in several ways to the current literature with regard to IQ and adaptive behavior. First, the estimated true mean population correlation between intelligence and adaptive behavior following correction for sampling error, measurement error, and range departure is moderate, indicating that intelligence and adaptive behavior are distinct, yet related, constructs. Second, IQ level has a moderating effect on the relation between IQ and adaptive behavior. The correlation is likely to be stronger at lower IQ levels, and weaker as IQ increases. Third, while not linear, age has an effect on the IQ/adaptive behavior relation. The population correlation is highest for very young children, and lowest for children between the ages of five and 12. Fourth, the magnitude of IQ/adaptive behavior correlations varies by disability type. The correlation is weakest for those without disability, and strongest for very young children with developmental delays. IQ/adaptive behavior correlations for those with ID are comparable to those with autism when not matched on IQ level. Fifth, the IQ/adaptive correlation when parents/caregivers serve as adaptive behavior respondents is comparable to when teachers act as respondents, but direct assessment of adaptive behavior results in a stronger correlation. Sixth, an individual's race does not significantly alter the correlation between IQ and adaptive behavior, but future research should evaluate the influence of race of the rater on adaptive behavior ratings. Seventh, the correlation between IQ and adaptive behavior varies depending on IQ measure used—the population correlation when Stanford-Binet scales are employed is significantly higher than when Wechsler scales are employed. And eighth, the correlation between IQ and adaptive behavior is not significantly different between adaptive behavior composite scores obtained from the Vineland, SIB, and ABAS families of adaptive behavior measures, which are among those that have been deemed appropriate for disability identification. Limitations of this study notwithstanding, it is the first to employ meta-analysis procedures and techniques to examine the correlation between intelligence and adaptive behavior and how moderators alter this relation. The results of this study provide information that can help guide practitioners, researchers, and policy makers with regard to the diagnosis or identification of intellectual and developmental disabilities.


- Posted using BlogPress from my iPad

Research Byte: Psychological and Cognitive Aspects of Borderline Intellectual Functioning : A Systematic Review

Psychological and Cognitive Aspects of Borderline Intellectual Functioning: A Systematic Review

Contena, B., & Taddei, S. (2017). Psychological and Cognitive Aspects of Borderline Intellectual Functioning. European Psychologist. Article link.
 
Bastianina Contena and Stefano Taddei
 

Abstract:

Borderline Intellectual Functioning (BIF) refers to a global IQ ranging from 71 to 84, and it represents a condition of clinical attention for its association with other disorders and its influence on the outcomes of treatments and, in general, quality of life and adaptation. Furthermore, its definition has changed over time causing a relevant clinical impact. For this reason, a systematic review of the literature on this topic can promote an understanding of what has been studied, and can differentiate what is currently attributable to BIF from that which cannot be associated with this kind of intellectual functioning. Using Preferred Reporting Items for Systematic Review and Meta-Analyses( PRISMA) criteria, we have conducted a review of the literature about BIF. The results suggest that this condition is still associated with mental retardation, and only a few studies have focused specifically on this condition.
 
Keywords: borderline intellectual functioning, borderline mental retardation, intellectual disability, systematic review


- Posted using BlogPress from my iPad

Stephen Greenspan on "Why DSM5 suggested a switch from adaptive behavior to adaptive reasoning": APA Div 33 featured conversation

 

My long time friend and professional colleague Dr. Stephen Greenspan, is conducting a featured conversation hour for Division 33 at the forthcoming APA convention in Denver.  He has provided me an advanced copy of his outline and has graciously given me permission to make it available at the ICDP blog.  A copy can be obtained by clicking here.

Stephen is one of the great "thinkers" in the field of intellectual disabilities.  Our professional lives crossed long distance when I was a doctoral student.  My advisor, Dr. Robert Bruininks, put me in charge of a series of studies investigating the constructs of adaptive and maladaptive behavior.  These studies eventually led to my dissertation--which was a CFA validation study of Greenspan's Model of Personal Competence (see 1990 reference below).  To the best of my knowledge, this was the first published article validating Greenspan's model.

Below are links to the various articles (I simply grabbed them from my MindHub web page--please visit if you want additional information).  Consistent with Stephen's outline notes, in this validated model of personal competence, conceptual intelligence was operationalized as measured by intelligence tests, and was not considered a domain of adaptive behavior.

Of interest is the recent study by MaCann et al. that provides structural (CFA) evidence for a separate cognitively oriented social-emotional construct, distinct from the other cognitive domains in the CHC taxonomy of human intelligence.  Although MaCann et al. refer to the construct as emotional intelligence, a reading of the dimensions suggest it could easily be called social intelligence.  

Finally, as Bruininks and I were pulled away from our AB/PC program of research for different reasons, I continue to be perplexed why other researchers have not tried to extend and refine the research on the model of personal competence, particularly given its prominence (and disagreements) in definitions of ID.

Adaptive Behavior and Personal Competence Research (select articles)

• Thompson, J. R., McGrew, K. S., & Bruininks, R. H. (2002).  Pieces of the puzzle. Measuring the personal competence and support needs of persons with intellectual disabilities. Peabody Journal of Education, 77(2), 23-29.
• Thompson, J., McGrew, K. & Bruininks, R. (1999).  Adaptive and maladaptive behavior.  Functional and structural characteristics.  In R. L. Schalock & D Braddock (Eds), Adaptive behavior and its measurement: Implications for the field of mental retardation(pp. 15-42).  Washington, DC.  American Association on Mental Retardation.
• Widaman, K. & McGrew K., (1996).  The structure of adaptive behavior.  In J.W. Jacobson & J.A. Mulick (Eds.), Manual of diagnosis and professional practice in mental retardation (pp. 97-110).  Washington, D.C.  American Psychological Association.
• McGrew, K., Bruininks, R., & Johnson, D. (1997).  Confirmatory factor analysis investigation of Greenspan's model of personal competence.  American Journal on Mental Retardation, 100(5) 533-545.
• Greenspan, S., & McGrew, K. (1996).  Response to Mathias and Nettlebeck on the structure of competence.  Need for theory-based methods to test theory-based questions.  Research in Developmental Disabilities, 17, 145-152.
• Bruininks, R., Chen, T., Lakin, C., & McGrew, K. (1992).  Components of personal competence and community integration for persons with mental retardation in small residential programs. Research in Developmental Disabilities, 13, 463-479.
• Ittenbach, R., Spiegel, A., McGrew, K., & Bruininks, R.  (1992). A confirmatory factor analysis of early childhood ability measures within a model of personal competence.  Journal of School Psychology, 30, 307-323.
• McGrew, K., Bruininks, R., & Thurlow, M. (1992). Relationship between measures of adaptive functioning and community adjustment for adults with mental retardation. Exceptional Children, 58, 517-529.
• McGrew, K., Ittenbach, R., Bruininks, R., & Hill, B. (1991). Factor structure of maladaptive behavior across the lifespan for persons with mental retardation. Research in Developmental Disabilities, 12, 181-199.
• McGrew, K., & Bruininks, R. (1990).  Defining adaptive and maladaptive behavior within a model of personal competence. School Psychology Review, 19, 53-73.
• McGrew, K., & Bruininks, R. (1989).  The factor structure of adaptive behavior. School Psychology Review, l8, 64-8l.
• Bruininks, R., McGrew, K., & Maruyama, G. (1988).  Structure of adaptive behavior in samples with and without mental retardation.  American Journal on Mental Retardation, 95(3), 265-272.

AAIDD "Death Penalty and Intellectual Disability" A Guide" is now available at AAIDD website!

The AAIDD ID and death penalty guide is now available at the AAIDD webpage!  Although the title is focused on the death penalty and ID (Atkins cases), having written two of the chapters (Flynn effect; Intellectual functioning), I believe all professionals in the field of psychological, assessment and ID should have this reference book--it presents recommendations for ID practice that go well beyond the official AAIDD classification book (the Green book) and are relevant to ID assessment practices in general.

Description of the guide at the AAIDD webpage.

• In the 2002 landmark decision Atkins v. Virginia 536 U.S. 304, the Supreme Court of the United States ruled that executing a person with intellectual disability is a violation of the Eighth Amendment of the U.S. Constitution, which prohibits “cruel and unusual punishment,” but left states to determine their own criteria for intellectual disability. AAIDD has always advocated against the death penalty for people with intellectual disability and has long provided amicus curiae briefs in Supreme Court cases. Thus, in this comprehensive new book published by AAIDD, notable authors in the field of intellectual disability discuss all aspects of the issues, with a particular focus on foundational considerations, assessment factors and issues, and professional concerns in Atkins assessments.

Title Correction: Determining Intellectual Disability in the Courts: Focus on Capital Cases

12-20-13 Correction note:  The title listed at the AAIDD web page differs from the official title for this guide as submitted by the editor of this volume, and agree upon by the contributors.  The current title, and expected publication title, is:

 Determining Intellectual Disability in the Courts:  Focus on Capital Cases


The Death Penalty and Intellectual Disability: A Guide is now listed as a forthcomming publication at the AAIDD publications web page. A brief description from that page follows below

In the 2002 landmark decision Atkins v. Virginia 536 U.S. 304, the Supreme Court of the United States ruled that executing a person with intellectual disability is a violation of the Eighth Amendment of the U.S. Constitution, which prohibits “cruel and unusual punishment,” but left states to determine their own criteria for intellectual disability. AAIDD has always advocated against the death penalty for people with intellectual disability and has long provided amicus curiae briefs in Supreme Court cases. Thus, in this comprehensive new book published by AAIDD, notable authors in the field of intellectual disability discuss all aspects of the issues, with a particular focus on foundational considerations, assessment factors and issues, and professional concerns in Atkins assessments.

The projected publication is sometime this spring.

Conflict of interest statement: I am the author of two of the chapters:

-Intellectual Functioning: Conceptual Issues
-Norm Obsolescence: The Flynn Effect


- Posted using BlogPress from my iPad

IAP101 Brief #12: Use of IQ component part scores as indicators of general intelligence in SLD and MR/ID diagnosis

   
            Historically the concept of general intelligence (g), as operationalized by intelligence test battery global “full scale” IQ scores, has been central to the definition and classification of individuals with a specific learning disability (SLD) as well as individuals with an intellectual disability (ID).  More recently, contemporary definitions and operational criteria have elevated intelligence test battery composite or part scores to a more prominent role in diagnosis and classification of SLD and more recently in ID.

            In the case of SLD, third-method “consistency” definitions prominently feature component or part scores in (a) the identification of consistency between low achievement and relevant cognitive abilities or processing disorders and (b) the requirement that an individual demonstrate relative cognitive and achievement strengths (see Flanagan, Fiorello & Ortiz, 2010).  The global IQ score is de-emphasized in the third-method SLD methods.

            In contrast, the 11^th edition of the AAIDD Intellectual Disability: Definition, Classification, and Systems of Supports manual (AAIDD, 2010) placed general intelligence, and thus global composite IQ scores, as central to the definition of intellectual functioning.  This has not been without challenge.  For example, the AAIDD ID definition has been criticized for an over-reliance on the construct of general intelligence and for ignoring contemporary psychometric theoretical and empirical research that has converged on a multidimensional hierarchical model of intelligence (viz., Cattell-Horn-Carroll or CHC theory).

The potential constraints of the “ID-as-a-general-intelligence-disability” definition was anticipated by the Committee on Disability Determination for Mental Retardation, in its National Research Council report “Mental Retardation:  Determining Eligibility for Social Security Benefits” (Reschly, Meyers & Hartel, 2001).  This national committee of experts concluded that “during the next decade, even greater alignment of intelligence tests and the IQ scores derived from them and the Horn-Cattell and Carroll models is likely.  As a result, the future will almost certainly see greater reliance on part scores, such as IQ scores for Gc and Gf, in addition to the traditional composite IQ.  That is, the traditional composite IQ may not be dropped, but greater emphasis will be placed on part scores than has been the case in the past” (Reschly et al., 2002, p. 94).  The committee stated that “whenever the validity of one or more part scores (subtests, scales) is questioned, examiners must also question whether the test’s total score is appropriate for guiding diagnostic decision making.  The total test score is usually considered the best estimate of a client’s overall intellectual functioning.  However, there are instances in which, and individuals for whom, the total test score may not be the best representation of overall cognitive functioning.” (p. 106-107).

            The increased emphasis on intelligence test battery composite part scores in SLD and ID diagnosis and classification raises a number of measurement and conceptual issues (Reschly et al., 2002).  For example, what are statistically significant differences?  What is a meaningful difference?  What appropriate cognitive abilities should serve as proxies of general intelligence when the global IQ is questioned?  What should be the magnitude of the total test score? 

Appropriate cognitive abilities will only be the only issue discussed here.  This issue addresses  which component or part scores are more correlated with general intelligence (g)—that is, what component part scores are high g-loaders?  The traditional consensus has been that measures of Gc (crystallized intelligence; comprehension-knowledge) and Gf (fluid intelligence or reasoning) are the highest g-loading measures and constructs and are the most likely candidates for elevated status when diagnosing ID (Reschly et al., 2002).  Although not always stated explicitly, the third method consistency SLD definitions specify that an individual must demonstrate “at least an average level of general cognitive ability or intelligence” (Flanagan et al., 2010, p.745), a statement that implicitly suggests cognitive abilities and component scores with high g-ness.

Table 1 is intended to provide guidance when using component part scores in the diagnosis and classification of SLD and ID (click on images to enlarge and use the browser zoom feature  to view; it is recommended you click here to access a PDF copy of the table..and also zoom in on it).  Table 1 presents a summary of the comprehensive, nationally normed, individually administered intelligence batteries that possess satisfactory psychometric characteristics (i.e., national norm samples, adequate reliability and validity for the composite g-score) for use in the diagnosis of ID and SLD.

The “Composite g-score” column lists the global general intelligence score provided by each intelligence battery.  This score is the best estimate of a person’s general intellectual ability, which currently is most relevant to the diagnosis of ID as per AAIDD.  All composite g-scores listed in Table 1 meet Jensen’s (1998) psychometric sampling error criteria as valid estimates of general intelligence.  As per Jensen’s number of tests criterion, all intelligence batteries g-composites are based on a minimum of nine tests that sample at least three primary cognitive ability domains.  As per Jensen’s variety of tests criterion (i.e., information content, skills and demands for a variety of mental operations), the batteries, when viewed from the perspective of CHC theory, vary in ability domain coverage—four (CAS, SB5), five (KABC-II, WISC-IV, WAIS-IV), six (DAS-II) and seven (WJ III) (Flanagan, Ortiz & Alfonso, 2007; Keith & Reynolds, 2010).   As recommended by Jensen (1998), “the particular collection of tests used to estimate g should come as close as possible, with some limited number of tests, to being a representative sample of all types of mental tests, and the various kinds of test should be represented as equally as possible” (p. 85).  Users should consult sources such as Flanagan et al. (2007) and Keith and Reynolds, 2010) to determine how each intelligence battery approximates Jensen’s optimal design criterion, the specific CHC domains measured, and the proportional representation of the CHC domains in each batteries composite g-score.

Also included in Table 1 are the component part scales provided by each battery (e.g., WAIS-IV Verbal Comprehension Index, Perceptual Reasoning Index, Working Memory Index, and Processing Speed Index), followed by their respective within-battery g-loadings.[1]  Examination of the g-ness of composite scores from existing batteries (see last three columns in Table 1) suggests the traditional assumption that measures of Gf and Gc are the best proxies of general intelligence may not hold across all intelligence batteries.[2] 

In the case of the SB5, all five composite part scores are very similar in g-loadings (h² = .72 to .79).  No single SB5 composite part score appears better than the other SB5 scores for suggesting average general intelligence (when the global IQ score is not used for this purpose).  At the other extreme is the WJ III where the Fluid Reasoning, Comprehension-Knowledge, Long-term Storage and Retrieval cluster scores are the best g-proxies for part-score based interpretation within the WJ III.  The WJ III Visual Processing and Processing Speed clusters are not composite part scores that should be emphasized as indicators of general intelligence.  Across all batteries that include a processing speed component part score (DAS-II, WAIS-IV, WISC-IV, WJ III) the respective processing speed scale is always the weakest proxy for general intelligence and thus, would not be viewed as a good estimate of general intelligence. 

            It is also clear that one cannot assume that composites with similar sounding names of measured abilities should have similar relative g-ness status within different batteries.  For example, the Gv (visual-spatial or visual processing) clusters in the DAS-II (Spatial Ability), SB5 (Visual-Spatial Processing) are relatively strong g-measures within their respective battery, but the same cannot be said for the WJ III Visual Processing cluster.  Even more interesting are the differences in the WAIS-IV and WISC-IV relative g-loadings for similarly sounding index scores. 

For example, the Working Memory Index is the highest g-loading component part score (tied with Perceptual Reasoning Index) in the WAIS-IV but is only third (out of four) in the WISC-IV.   The Working Memory Index is comprised of the Digit Span and Arithmetic subtests in the WAIS-IV and the Digit Span and the Letter-Number Sequencing subtests in the WISC-IV.  The Arithmetic subtest has been reported to be a factorially complex test which may tap fluid intelligence (Gf-RQ—quantitative reasoning), quantitative knowledge (Gq), working memory (Gsm), and possible processing speed (Gs; Keith & Reynolds, 2010; Phelps, McGrew, Knopik & Ford, 2005).   The factorially complex characteristics of the Arithmetic subtest (which, in essence, makes it function like a mini-g proxy) would explain why the WAIS-IV Working Memory Index is a good proxy for g in the WAIS-IV but not in the WISC-IV. The WAIS-IV and WISC-IV Working Memory Index scales, although named the same, are not measuring identical constructs.

A critical caveat is that the g-loadings cannot be compared across different batteries.  g-loadings may change when the mixture of measures included in the analyses change.  Different "flavors" of g can result (Carroll, 1993; Jensen, 1998). The only way to compare the g-ness across batteries is with appropriately designed cross- or joint-battery analysis (e.g., WAIS-IV, SB5 and WJ III analyzed in a common sample).

The above within and across intelligence battery examples illustrates that those who use component part scores as an estimate of a person’s general intelligence must be aware of the composition and psychometric g-ness of the component scores within each intelligence battery.  Not all component part scores in different intelligence batteries are created equal (with regard to g-ness).  Also, not all similarly named factor-based composite scores may measure the same identical construct and may vary in degree of within battery g-ness.  This is not a new problem in the context of naming factors in factor analysis, and by extension, factor-based intelligence test composite scores, Cliff (1983) described this nominalistic fallacy in simple language—“if we name something, this does not mean we understand it” (p. 120). 

---

[1] As noted in the footnotes in Table 1, all composite score g-loadings were computed by Kevin McGrew by entering the smallest number (and largest age ranges covered) of the published correlation matrices within each intelligence batteries technical manual (note the exception for the WJ III) in order to obtain an average g-loading estimate.  It would have been possible to calculate and report these values for each age-differentiated correlation matrix for each intelligence battery.  However, the purpose of this table is to provide the best possible average value across the entire age-range of each intelligence battery.  Floyd and colleagues have published age-differentiated g-loadings for the DAS-II and WJ III.  Those values were not used as they are based on the use of the principal common factor analysis method, a method that  analyzes the reliable shared variance among tests.  Although principal factor and principal component loadings typically will order measures in the same relative position, the principal factor loadings typically will be lower.  Given that the imperfect manifest composite scale scores are those that are utilized in practice, and to also allow uniformity in the calculation of the g-loadings reported in Table 1, principal component analysis was used in this work. The same rationale was used for not using the latent factor loadings on a higher-order g-factor in SEM/CFA analysis of each test battery.  Loadings from CFA analyses represent the relations between the underlying theoretical ability constructs and g purged of measurement error.  Also, frequently the final CFA solutions reported in a batteries technical manual (or independent journal articles) allow tests to be factorially complex (load on more than one latent factor), a measurement model that does not resemble the real world reality of the manifest/observed composite scores used in practice.  Latent factor loadings on a higher-order g-factor will often differ significantly from principal component loadings based on the manifest measures, both in absolute magnitude and relative size (e.g., see high Ga loading on g in WJ III technical manual which is at variance with the manifest variable based Ga loading reported in Table 1) 

[2] The h² values are the values that should be used to compare the relative amount of g-variance present in the component part scores within each intelligence battery.