Supreme Court to consider the role of #IQ tests in ban on executing people who are #intellectually disabled (#ID)- #SCOTUSblog: #schoolpsychology #schoolpsychologists #intelligence

An email quick-blog post FYI.

 

If you want more information, including amicus briefs for the defendent from professional groups (APA, AAIDD), visit a special post at IQs Corner blog—-

 

Court to consider the role of IQ tests in ban on executing people who are intellectually disabled - SCOTUSblog 
https://www.scotusblog.com/2025/12/court-to-consider-the-role-of-iq-tests-in-ban-on-executing-people-who-are-intellectually-disabled/

Pardon typos and spelling errors-Message may be sent from iPhone and I've always had spelling problems :)
 

 

*****************************************
Kevin S. McGrew, PhD
Educational & School Psychologist
Director
Institute for Applied Psychometrics (IAP)
https://www.themindhub.com
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The evolution of the Woodcock-Johnson (WJ--WJ IV) global IQ or g scores - The WJ is the Elon Musk of IQ testing

 Across the various editions of the WJ Tests of Cognitive Abilities (WJ, WJ-R, WJ III, WJ IV), the authors continually have sought to improve the measurement of intelligence via following contemporary research and theory.  As a result, in contrast to many other IQ tests, the WJ has been known for global IQ scores (original called Broad Cognitive Ability, later changed to General Intellectual Ability) that changed rather dramatically from one revision to the next.  We the WJ authors might be considered to be the Elon Musk of IQ test development.

I was recently asked to explain the changing nature of the BAC/GIA scores.  The result is the table inserted below (double click to enlarge).  I believe the table is self-explanatory.  A nice PDF copy can be downloaded here.  Enjoy.

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.

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How to raise a societies average intelligence—education : A meta-analysis

How Much Does Education Improve Intelligence? A Meta-Analysis.
Psychological Science 1 –12. Article link.

Stuart J. Ritchie and Elliot M. Tucker-Drob

Abstract

Intelligence test scores and educational duration are positively correlated. This correlation could be interpreted in two ways: Students with greater propensity for intelligence go on to complete more education, or a longer education increases intelligence. We meta-analyzed three categories of quasiexperimental studies of educational effects on intelligence: those estimating education-intelligence associations after controlling for earlier intelligence, those using compulsory schooling policy changes as instrumental variables, and those using regression-discontinuity designs on school-entry age cutoffs. Across 142 effect sizes from 42 data sets involving over 600,000 participants, we found consistent evidence for beneficial effects of education on cognitive abilities of approximately 1 to 5 IQ points for an additional year of education. Moderator analyses indicated that the effects persisted across the life span and were present on all broad categories of cognitive ability studied. Education appears to be the most consistent, robust, and durable method yet to be identified for raising intelligence.

From summary

The results reported here indicate strong, consistent evidence for effects of education on intelligence. Although the effects—on the order of a few IQ points for a year of education—might be considered small, at the societal level they are potentially of great conse-quence. A crucial next step will be to uncover the mechanisms of these educational effects on intelligence in order to inform educational policy and practice.


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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.


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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


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Sixth Circuit Court of Appeals rules (Black v Carpenter, 2017) against norm obsolescence (Flynn effect) adjustment of IQ scores in Atkins death penalty cases

A newly published 6th Circuit opinion (Black v Carpenter, 2017) rules against norm obsolescence (the Flynn effect) in the evaluation of IQ test scores in Atkins ID death penalty cases.  I obviously disagree with this decision as outlined in my 2015 chapter in the AAIDD "The Death Penalty and Intellectual Disability" (Polloway, 2015).

I have no further comment at this time as my expert opinion is clearly articulated in the AAIDD publication and I will continue my efforts to educate the courts.  This decision is at variance with the official positions of American Association on Intellectual and Developmental Disabilities (AAIDD) and the American Psychiatric Association (DSM-5), the two professional associations with official  guidance regarding  the diagnosis of ID. 

This looks like another issue that might need the attention of SCOTUS.

The following section is extracted from the complete ruling.


E. Implications of the Flynn Effect

There is good reason to have pause before retroactively adjusting IQ scores downward to offset the Flynn Effect. As we noted above, see n.1, supra, the Flynn Effect describes the apparent rise in IQ scores generated by a given IQ test as time elapses from the date of that specific test’s standardization. The reported increase is an average of approximately three points per decade, meaning that for an IQ test normed in 1995, an individual who took that test in 1995 and scored 100 would be expected to score 103 on that same test if taken in 2005, and would be expected to score 106 on that same test in 2015. This does not imply that the individual is “gaining intelligence”: after all, if the same individual, in 2015, took an IQ test that was normed in 2015, we would expect him to score 100, and we would consider him to be of the same “average” intelligence that he demonstrated when he scored 100 on the 1995-normed test in 1995. Rather, the Flynn Effect implies that the longer a test has been on the market after initially being normed, the higher (on average) an individual should perform, as compared with how that individual would perform on a more recently normed IQ test.

At first glance, of course, the Flynn Effect is troubling: if scoring 70 on an IQ test in 1995 would have been sufficient to avoid execution, then why shouldn’t a score of 76 on that same test administered in 2015 (which would produce a “Flynn-adjusted” score of 70) likewise suffice to avoid execution? Further, even if IQ tests were routinely restandardized every year or two to reset the mean score to 100, and even if old IQ tests were taken off the market so as to avoid the Flynn Effect “inflation” of scores that is visible when an IQ test continues to be administered long after its initial standardization, that would only mask, but not change, the fact that IQ scores are said to be rising.

Indeed, perhaps the most puzzling aspect of the Flynn Effect is that it is true. As Dr. Tassé states in his declaration, “[t]he so-called ‘Flynn Effect’ is NOT a theory. It is a wellestablished scientific fact that the US population is gaining an average of 3 full-scale IQ points per decade.” The implications of the Flynn Effect over a longer period of time are jarring: consider a cohort of individuals who, in 1917, took an IQ test that was normed in 1917 and received “normal” scores (say, 100, on average). If we could transport that same cohort of individuals to the present day, we would expect their average score today on an IQ test normed in 2017—a century later—to be thirty points lower: 70, making them mentally retarded, on average.

Alternatively, consider a cohort of individuals who, in 2017, took an IQ test that was normed in 2017 and received “normal” scores (of 100, on average). If we could transport that same cohort of individuals to a century ago, we would expect that their average score on a test normed in 1917 would be thirty points higher: 130, making them geniuses, on average.

It thus makes little sense to use Flynn-adjusted IQ scores to determine whether a criminal is sufficiently intellectually disabled to be exempt from the death penalty. After all, if Atkins stands for the proposition that someone with an IQ score of 70 or lower in 2002 (when Atkins was decided) is exempt from the death penalty, then the use of Flynn-adjusted IQ scores would conceivably lead to the conclusion that, within the next few decades, almost no one with borderline or merely below-average IQ scores should be executed, because their scores when adjusted downward to 2002 levels would be below 70. Indeed, the Supreme Court did not amplify just what moral or medical theory led to the highly general language that it used in Atkins when it prohibited the imposition of a death sentence for criminals who are “so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus,” 536 U.S. at 317. If Atkins had been a 1917 case, the majority of the population now living—if we were to apply downward adjustments to their IQ scores to offset the Flynn Effect from 1917 until now—would be too mentally retarded to be executed; and until the Supreme Court tells us that it is committed to making such downward adjustments, we decline to do so.

* * *

COLE, Chief Judge, concurring in the opinion except for Section II.E. I concur with the majority opinion except as to the section discussing the implications of the Flynn Effect. In holding that Black did not prove that he had significantly subaverage general intellectual functioning, we concluded that Black’s childhood IQ scores would be above 70 even if we adjusted those scores to account for both the SEM and the Flynn Effect. Accordingly, I would not address the question of whether we should apply a Flynn Effect adjustment in cases generally because it is unnecessary to the resolution of Black’s appeal. Regardless, courts, including our own in Black I, have regarded the Flynn Effect as an important consideration in determining who qualifies as intellectually disabled. See, e.g., Black v. Bell, 664 F.3d 81, 95–96 (6th Cir. 2011); Walker v. True, 399 F.3d 315, 322–23 (4th Cir. 2005).

Research Byte: The Predictive Validity of Four Intelligence Tests for School Grades: A Small Sample Longitudinal Study in Germany

The Predictive Validity of Four Intelligence Tests for School Grades: A Small Sample Longitudinal Study

Jasmin T. Gygi, Priska Hagmann-von Arx^*, Florine Schweizer and Alexander Grob

• Department of Psychology, University of Basel, Basel, Switzerland

Intelligence is considered the strongest single predictor of scholastic achievement. However, little is known regarding the predictive validity of well-established intelligence tests for school grades. We analyzed the predictive validity of four widely used intelligence tests in German-speaking countries: The Intelligence and Development Scales (IDS), the Reynolds Intellectual Assessment Scales (RIAS), the Snijders-Oomen Nonverbal Intelligence Test (SON-R 6-40), and the Wechsler Intelligence Scale for Children (WISC-IV), which were individually administered to 103 children (M_age = 9.17 years) enrolled in regular school. School grades were collected longitudinally after 3 years (averaged school grades, mathematics, and language) and were available for 54 children (M_age = 11.77 years). All four tests significantly predicted averaged school grades. Furthermore, the IDS and the RIAS predicted both mathematics and language, while the SON-R 6-40 predicted mathematics. The WISC-IV showed no significant association with longitudinal scholastic achievement when mathematics and language were analyzed separately. The results revealed the predictive validity of currently used intelligence tests for longitudinal scholastic achievement in German-speaking countries and support their use in psychological practice, in particular for predicting averaged school grades. However, this conclusion has to be considered as preliminary due to the small sample of children observed.

Why are full scale IQ scores often lower (or higher) than the subscores? Dr. Joel Schneider on the "composite score extremity effect"

Bingo.  There is finally an excellent, relatively brief, explanation of the phenomena of why full scale IQ scores often diverge markedly from the arithmetic average of the component index or subtest scores.

This composite score extremity effect (Schneider, 2016)  has been well known by users of the WJ batteries.  Why....because the WJ has placed the global IQ composite and the individual tests on the same scale (M=100; SD=15).  In contrast, most other cognitive ability batteries (e.g., Wechslers) have the individual test scores on a different scale (M=10; SD=3).  The use of different scales has hidden this statistical score effect from users.  It has always been present.  I have written about this many times.  One can revisit my latest post on this issue here.

Now that the WISC-V measures a broader array of cognitive abilities (e.g., 5 index scores), users have been asking the same "why does the total IQ score not equal the average of the index scores?"  Why?  Because the five index scores are on the same scale as the full scale IQ score...and thus this composite score extremity effect is not hidden.  A recent thread on the NASP Community Exchange provides examples of psychologists wondering about this funky test score issue (click here to read).

As per usual, Dr. Schneider has provided intuitive explanations of this score effect, and for those who want more, extremely well written technical explanations.

The WJ IV ASB 7 can be downloaded by clicking here.  Although written in the context of the WJ IV, this ASB is relevant to all intelligence test batteries that provide a global IQ score that is the sum of part scores.

Kudos to Dr. Schneider.

Click on image to enlarge

AAIDD chapters on intellectual functioning and the Flynn effect - overdue post

I just made this post over at the Intellectual Competence and Death Penalty blog and am repeating it here for interested readers.

(Click on image to enlarge)

It has been along time since I've been able to devote time to any of my three professional blogs.  I have been unbelievably busy with travel and professional presentations.  In fact, I have been so busy that I failed to feature two of my own recent Atkin's death penalty related book chapters that appeared in the new AAIDD book "Determining Intellectual Disability in the courts: Focus on capital cases." I have made these two chapters available via the MindHub web portal but do not believe I featured them at this blog (or at IQ's Corner).  One chapter deals with assessment of intellectual functioning issues and the other IQ test norm obsolescence (aka., the Flynn Effect).  The references (with links) are below.

McGrew, K. (2015a). Intellectual functioning. In Polloway, E. (Ed.), Determining Intellectual Disability in the courts: Focus on capital cases (pp. 85-111). Washington, DC: American Association on Intellectual and Developmental Disabilities.

McGrew, K. (2015b). Norm obsolescence: The Flynn Effect. In Polloway, E. (Ed.), Determining Intellectual Disability in the courts: Focus on capital cases (pp. 155-169). Washington, DC: American Association on Intellectual and Developmental Disabilities

Cognitive ability testing: The big picture perspective. A slide show

CHC theory 101: Introduction to "big picture" context from Kevin McGrew

SCOTUS Hall v Florida Atkins ID update: Petitioners and Amicus Briefs--major focus on IQ "bright line" and SEM

The Atkins MR/ID case of Hall v Florida, which is to be heard by SCOTUS this spring, had two mportant briefs posted within the last week.

The Hall v Florida petition was filed Dec 16. Today, an Amicus Brief was filed by a number of organizations, led by the American Psychological Association.
Click here for a variety of posts re: Atkins cases in Flordia, which have been problematic due to the Florida "Cherry court" establishment of a "bright line" score of 70, with no consiseration of the standard error of measurement (SEM)

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IQ test "practice effects"

A practice effect is a major psychometric issue in many Atkins cases, given that both the state and defense often test the defendant with the same IQ battery (most often a Wechsler), and often within a short test-retest interval. Click here to view all ICDP posts that mention practice effects.

Dr. Alan Kaufman has summarized the majority of the literature on practice effects on the Wechslers. He published an article in The Encyclopedia of Intelligence (1994; Edited by Robert Sternberg) that summarized the research prior to the third editions of the Wechsler scales. That article is available on-line (click here).

The most recent summary of the contemporary Wechsler practice effect research is in Lichtenberger and Kaufman (2009) Essentials of WAIS-IV Assessment (p. 306-309). The tables and text provide much about WAIS-IV and some about WAIS-III. The best source for WAIS-III is Kaufman and Lichtenberger, Assessing Adolescent and Adult Intelligence (either the 2002 second edition or the 2006 third edition), especially Tables 6.5 and 6.6 (2006 edition). Below are a few excerpts from the associated text from the 2006 edition

"Practice effects on Wechsler's scales tend to be profound, particularly on the Performance Scale" (p. 202)

"predictable retest gains in IQs" (p.202)

"On the WAIS-III, tests with largest gains are Picture Completion, Object Assembly, and Picture Arrangement"

"Tests with smallest gains are Matrix Reasoning (most novel Gf test), Vocabulary and Comprehension

Block Design improvement most likely due to speed variance--"on second exposure subjects may be able to respond more quickly, thereby gaining in their scores" (p. 204)

One year interval results in far less pronounced practice effects (p. 208).

"The impact of retesting on test performance, whether using the WAIS-III, WAIS-R, other Wechsler scales, or similar tests, needs to be internalized by researchers and clinicians alike. Researchers should be aware of the routine and expected gains of about 2 1/2 points in V-IQ for all ages between 16 and 89 years. They should also internalize the relatively large gain on P-IQ for ages 16-54 (about 8 to 8 1/2 points), andn the fact that this gain in P-IQ swindles in size to less than 6 points for ages 55-74 and less than 4 points for ages 75-889" (p. 209).

"Increases in Performance IQ will typically be about twice as large as increases in Verbal IQ for individuals ages 16 to 54" (p. 209)

Finally, the latest AAIDD manual provides professional guidance on the practice effect.


"The practice effect refers to gains in IQ scores on test of intelligence that result from a person being retested on the same instrument" (p. 38)

"..established clinical practice is to avoid administering the same intelligence test within the same year to the same individual because it will often lead to an overestimate of the examinee's true intelligence" (p. 38).


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Two new Atkins MR/ID death penalty Flynn Effect articles

Two new articles published regarding the issue of adjusting IQ scores for the Flynn Effect in Atkins MR/ID death penalty cases. These will be included in an update of the ICDP Flynn Effect archive project which I hope to complete by the end of the week.

Looking to science rather than convention in adjusting IQ scores when death is at issue. 2010 Volume 41, Issue 5 (Oct), p. 413-419. Professional Psychology: Research and Practice. Cunningham, Mark D.; Tassé, Marc J.

Abstract

The progressive obsolescence of IQ test norms and associated score inflation (i.e., the Flynn effect) may have literal life and death significance in capital mental retardation determinations (i.e., Atkins hearings). Hagan, Drogin, and Guilmette (2008) asserted that IQ score corrections for the Flynn effect were inconsistent with a “standard of practice” they deduced from custom, convention, and authority. More accurately, this reflected a proposed practice guideline or recommendation for practice, rather than a standard of practice. Whether a proposed guideline or recommendation for practice, these are better informed by an analysis of the available science than accepted convention. The authors reviewed research findings regarding the occurrence of the Flynn effect in the “zone of ambiguity” (IQ = 71–80), and proposed a best practice recommendation for discussing and reporting Flynn effect correction of IQ scores in capital mental retardation determinations.


Science rather than advocacy when reporting IQ scores, p. 420-423. Hagan, Leigh D.; Drogin, Eric Y.; Guilmette, Thomas J.

Abstract

The existence of shifts in mean IQ scores over time is well established. However, on a case-by-case basis, such shifts vary unreliably, rendering specific adjustments to a given individual's IQ score incalculable. Based upon data presented previously (Hagan, Drogin, & Guilmette, 2008) as well as a review of more recent studies that have further detailed the wide variability of mean score shifts, any proposal to “correct” IQ scores in forensic evaluations due to the “Flynn effect” (FE) is unjustifiable. To offer the court an unreliable new IQ score in place of an allegedly unreliable old one—and to do so specifically in capital murder cases as opposed to any other context—appears far more reflective of result-focused advocacy than objective scientific practice. Forensic psychologists are explicitly encouraged to address likely ranges of IQ score variability and to discuss in relevant detail the strengths and weaknesses of the specific studies—however much at odds these may be—that attempt to define and quantify mean score shifts.

Flynn effect IQ scores Atkins cases Death penalty capital punishment norm obsolescence ICDP blog Psychologists forensic psychology neuropsychology school psychology Intelligence IQ tests mental retardation intellectual disability

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The Flynn Effect report series: What is the Flynn Effect: IAP AP101 Report #6

A new IAP Applied Psychometrics 101 report (#6) is now available.  The report is the first in the Flynn Effect series, a series of brief reports that will define, explain and discuss the validity of the Flynn Effect (click here to access all prior FE related posts at the ICDP blog) and the issues surrounding the application of a FE "adjustment" for scores based on tests with date norms (norm obsolescence), particularly in the context of Atkins MR/ID capital punishment cases.  The abstract for the brief report is presented below.  The report can be accessed by clicking here.

Norm obsolescence is recognized in the intelligence testing literature as a potential source of error in global IQ scores.  Psychological standards and assessment books recommend that assessment professionals use tests with the most current norms to minimize the possibility of norm obsolescence spuriously raising an individual’s measured IQ.  This phenomenon is typically referred to as the Flynn Effect.  This report is the first in a series of brief reports the will define, explain, and summarize the scholarly consensus regarding the validity of the Flynn Effect.  The series will conclude with an evaluation of the question whether a professional consensus has emerged regarding the practice of adjusting dated IQ test scores for the Flynn Effect, an issue of increasing debate in Atkins MR/ID capital punishment hearings.

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Psychometric PS to Johnston v Florida (2010) denied appeal re: new WAIS-IV scores

This is a follow-up to my brief comments yesterday regarding the Johstone v Fl (2010) denied MR/ID appeal of two days ago.

As mentioned in the decision and my blog comment, the WAIS-III/WAIS-IV tests correlated .94 in a study reported in the WAIS-IV technical manual.  This is a very high correlation...but does NOT mean that the two tests should be expected to provide identical IQ scores.  I discuss these issues in a prior IAP AP101 report.

The tests have different norm dates and thus, the later version (WAIS-IV) would be expected to provide a lower score based on the Flynn effect.  More importantly, as reported in the IAP AP101 report, when one calculates the standard deviation of the difference score (see page 6 of that report) for a correlation of .94, the resulting value is 5.2 (round to 5 for ease of discussion).  This means that, on average, the WAIS-III/WAIS-IV (even if highly correlated at the .94 level) would in the general population be expected to display a range of difference scores from -5 to +5...or a range of 10 IQ points......in 68% of the population.  Please review that prior report for further explanation and discussion.

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Research Bytes: 3-24-10: WAIS-III/WISC-IV score differences in spec. ed. population

Gordon, S., Duff, S., Davidson, T., & Whitaker, S. (2010). Comparison of the WAIS-III and WISC-IV in 16-Year-Old Special Education Students. Journal of Applied Research in Intellectual Disabilities, 23(2),
197-200.


Abstract:

Previous research with earlier versions of the WISC and WAIS has demonstrated that when administered to people who have intellectual disabilities, the WAIS produced higher IQ scores than the WISC. The aim of this study was to examine whether these differences still exist. A comparison of the Wechsler Adult Intelligence Scale - Third Edition (WAIS-III) with the Wechsler Intelligence Scale for Children - Fourth Edition (WISC-IV) was conducted with individuals who were 16?years old and receiving special education. Materials and Methods

All participants completed the WAIS-III (UK) and WISC-IV (UK). The order of administration was counterbalanced; the mean Full Scale IQ and Index scores on the WAIS-III and WISC-IV were compared. Results

The WAIS-III mean Full Scale IQ was 11.82 points higher than the mean Full Scale IQ score on the WISC-IV. Significant differences were also found between the Verbal Comprehension Index, Perceptual Reasoning/Organization Index and Processing Speed Index on the WAIS-III and WISC-IV, all with the WAIS-III scoring higher. Conclusions

The findings suggest that the WAIS-III produces higher scores than the WISC-IV in people with intellectual disabilities. This has implications for definitions of intellectual disability and suggests that Psychologists should be cautious when interpreting and reporting IQ scores on the WAIS-III and WISC-IV.

Keywords: intellectual disability diagnosis; intelligence test; WAIS-III; WISC-IV

Technorati Tags: psychology, forensic psychology, forensic psychiatry, neuropsychology, intelligence, school psychology, educational psychology, IQ, IQ tests, IQ scores, intellectual disability, mental retardation, MR, ID, criminal psychology, criminal defense, ABA, American Bar Association, Atkins cases, death penalty, capital punishment, AAIDD, WAIS-III, WISC-IV, Wechsler batteries, psychometrics

The Wechsler-like IQ subtest scaled score metric: The potential for misuse, misinterpretation and impact on critical life decisions---draft report in search of feedback

The following are the first three paragraphs (and a critical figure) of a draft of an IAP Applied Psychometrics 101 Brief Report (#5).  The complete report can be download in PDF format by clicking here.  A web-page version of the complete report can be found by clicking here (note - the web page verision may NOT display two embedded figures....viewing the PDF copy may be necessary)

I'm providing this initial draft report with the expressed intent of soliciting feedback and comments regarding the accuracy and soundness of my analyses and logic.  I'm looking for critical feedback to improve the report.  This is a draft report that will be revised if comments suggest important changes.  Please read it in the spirit of "tossing out some critical ideas" for reflective analysis and feedback.  Feedback can be sent directly to me (iap@earthlink.net) or could be provided in the form of listserv thread discussions at the NASP and/or CHC listservs.


I've recently been skimming James Flynn's new book (What is Intelligence:  Beyond the Flynn Effect) to better understand the methodology and interpretation of the Flynn effect. Of particular interest to me (as an applied measurement person) is his analysis of the individual subtest scores from the various Wechsler scales across time. As most psychologists know, Wechsler subtest scaled scores (ss) are on a scale with a mean (M) = 10 and a standard deviation (SD) = 3. The subtest ss range from 1 to 19.  In Appendix 1 of his book, Flynn states "it is customary to score subtests on a scale in which the SD is 3, as opposed to IQ scores which are scaled with SD set at 15. To convert to IQ, just multiply subtest gains by five, as was done to get the IQ gains in the last column."  At first glance, this statement makes it sound as if the transformation of subtest ss to IQ SS is an easy (“just multiply….”; emphasis added by me) and mathematically acceptable procedure without problems. However, on close inspection this transformation has the potential to introduce unknown sources of error into the precision of the transformed SS scores.  It is the goal of this brief technical post to explain the issues involved when making this ss-to- IQ SS conversion.

The ss 1-19 scale has a long history in the Wechsler batteries. For sample, in Appendix 1 of Measurement of Adult Intelligence (Wechsler, 1944), Wechsler described the steps used to translate subtest raw scores to the new ss metric. The Wechsler batteries have continued this tradition in each new revision, although the methodology and procedures to calculate the ss 1-19 values have become more sophisticated over time.   Although the methods used to develop the Wechsler ss 1-19 scale may have become more sophisticated, the resultant underlying scale for each subtest has not…scores still range from 1-19 (M=10; SD=3).  Also, the most recent Stanford-Binet—5th Edition (SB5; Roid, 2003) and Kaufman Assessment Battery for Children-2nd Edition (KABC-II) have both adopted the same ss 1-19 scale for their respective individual subtests.

Why is this relatively crude (to be defined below) scale metric still used in some intelligence batteries when other contemporary intelligence batteries provide subtest scale metrics with finer measurement resolution?  For example, the DAS-II (Elliott, 2007) places individual test scores on the T-scale (M=50; SD=10), with scores that range from 10-90.  The WJ III (McGrew & Woodcock, 2001) places all test and composite scores on the standard score (SS) metric associated with full scale and composite scores (M=100; SD=15).  The critical question to be asked is “are there advantages or disadvantages to retaining the historical ss 1-19 scale or, are their real advantages to having individual test scales with finer measurement resolution (DAS-II; WJ III)?”

......continued............
(complete report available at links in first paragraph of this post)

[Double click on image to enlarge]

Technorati Tags: psychology, Flynn Effect,school psychology, educational psychology, neuropsychology, forensice psychology, criminal psychology, criminal justice, psychometrics, Wechslers, WISC-III, WISC-IV, WAIS-III, WAIS-IV, WJ III, DAS-II, KABC-II, SB5, intelligence, IQ tests, IQ scores, scaled scores, MR, ID, mental retardation, intellectual disability, capital punishment, death penalty, IAP AP101 report

Dssertation Dish: Woodcock -- Johnson and KABC-profile research

Validation of neuropsychological subtypes of learning disabilities by Hiller, Todd R., Ph.D., Ball State University, 2009 , 99 pages; AAT 3379243

Abstract

The present study used archival data of individuals given the Woodcock-Johnson Tests of Cognitive Abilities 3 rd Edition and the Woodcock-Johnson Tests of Achievement 3 rd Edition in an effort to define subtypes of LD. The sample included 526 subjects aged 6 years to 18 years old who had a diagnosis of some type of LD. Of these, 22.7% had an additional diagnosis other than LD. It was expected that subtypes similar to Rourke's classification of his nonverbal learning disorder and his basic phonological processing disorder would be found.

Portions of the battery were used in a latent class cluster analysis in order to determine group patterns of strengths and weaknesses. Using the Lo-Mendell-Rubin test, a 3 solution model was selected. These three groups showed no evidence of patterns of strengths and weaknesses. These groups were best described as a high, middle, and low group, in that the high group had scores that were universally larger than scores from the middle group, which had scores that were universally higher than the low group. The rates of individuals with comorbid disorders varied greatly between the clusters. The high group had the lowest comorbidity rates in the study, with only 6.8%. That is compared to 26.4% of the middle group and 44.8% of the low group.

These results suggest that clusters found differ more in severity rather than types of LD. Individuals with LD and comorbid disorders are more likely to have more severe deficits.

Profile analysis of the Kaufman Assessment Battery for Children, Second Edition with African American and Caucasian preschool children by Dale, Brittany Ann, Ph.D., Ball State University, 2009 , 130 pages; AAT 3379238

Abstract

The purpose of the present study was to determine if African American and Caucasian preschool children displayed similar patterns of performance among the Cattell-Horn-Carroll (CHC) factors measured by the Kaufman Assessment Battery for Children, Second Edition (KABC-II). Specifically, a profile analysis was conducted to determine if African Americans and Caucasians displayed the same patterns of highs and low and scored at the same level on the KABC-II composites and subtests. Forty-nine African American (mean age = 59.14 months) and 49 Caucasian (mean age = 59.39) preschool children from a Midwestern City were included in the study and were matched on age, sex, and level of parental education. Results of a profile analysis found African American and Caucasian preschool children had a similar pattern of highs and lows and performed at the same level on the CHC broad abilities as measured by the KABC-II. Comparison of the overall mean IQ indicated no significant differences between the two groups. The overall mean difference between groups was 1.47 points, the smallest gap seen in the literature. This finding was inconsistent with previous research indicating a one standard deviation difference in IQ between African Americans and Caucasians. A profile analysis of the KABC-II subtests found the African American and Caucasian groups performed at an overall similar level, but did not show the same pattern of highs and lows. Specifically, Caucasians scored significantly higher than African Americans on the Expressive Vocabulary subtest which measures the CHC narrow ability of Lexical Knowledge.

Results of this study supported the KABC-II's authors' recommendation to make interpretations at the composite level. When developing hypotheses of an individual's strengths and weaknesses in narrow abilities, clinicians should be cautious when interpreting the Expressive Vocabulary subtest with African Americans. Overall, results of this study supported the use of the KABC-II with African American preschool children. When making assessment decisions, clinicians can be more confident in an unbiased assessment with the KABC-II.

Future research could further explore the CHC narrow abilities in ethnically diverse populations. Additionally, more research should be conducted with other measures of cognitive ability designed to adhere to the CHC theory, and the appropriateness of those tests with an African American population. Furthermore, future research with the KABC-II could determine if the results of the present study were replicated in other age groups.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, special education, IQ, IQ test, CHC, Cattlll -Horn-Caroll, intelligene, disseration dish, IQs Corner, profiles

New IAP Applied Psychometrics 101 Report: IQ scores and SEM

A new IAP Applied Psychometrics 101 report (#5) is now available.  The title of the report and abstract is below.  The report can be downloaded by clicking here.

Applied Psychometrics 101 #4:  The Standard Error of Measurement (SEM):  An Explanation and Facts for "Fact Finders" in Atkins MR/ID death penalty proceedings.

Abstract

The standard error of measurement (SEM) is a professionally accepted and scientifically based measurement concept that allows users of psychological test scores to account for the known degree of imprecision in the scores.  Atkins MR/ID cases almost always involve standardized psychological testing in the domains of intelligence (IQ tests) and adaptive behavior (AB).  Scores from IQ and AB measures are fallible—not perfectly reliable.  This report provides an easy to understand explanation of the psychometric concept of SEM augmented by an example based on real-world data.  The report concludes with 8 SEM facts that “fact finders” should understand and internalize when evaluating psychological test data during legal proceedings--Atkins MR/ID death penalty proceedings in particular.

Here is a visual treat/tease from the report:

All prior IAP AP101 reports can be accessed via the Applied Psychometrics 101 (AP101) Reports section of the blog--on the blog sidebar.

Technorati Tags: psychology, forensice psychology, criminal psychology, school psychology, educational psychology, neuropsychology, developmental disabilities, MR, ID, mental retardation, intlellectual disability, AAIDD, Joint Test Standards, psychometrics, psychological measures, applied psychometrics, SEM, standard error or measurement, reliability, measurement error, Atins cases, death penalty, capital punishment, adpative behavior, intelligence, IQ, IQ tests, IQ scores, ICDP