Neurodiversity and Intelligence: Evaluating the Flynn Effect in Children with Autism Spectrum Disorder

The Flynn Effect (FE) among child and adolescent populations indicates that intelligence scores improve by about three points per decade. Using nine years of data from the National Database for Autism Research, this study examined whether general intelligence changed significantly for nine cohorts with autism spectrum disorder (ASD; N = 671). Analyses demonstrated a downward trend such that Cohen's d from 1998 to 2006 was - 0.27. The mean IQ is 92.74 for years 1-3, 91.54 for years 4-6, and 87.34 for years 7-9, indicating a reverse FE of 5.4 points per decade. A linear regression revealed a significant negative FE comparable to the positive effect of age on IQ among those with ASD. Implications for research, practice, and law are discussed.

Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions

This study investigated the systematic rise in cognitive ability scores over generations, known as the Flynn Effect, across middle childhood and early adolescence (7-15 years; 291 monozygotic pairs, 298 dizygotic pairs; 89% White). Leveraging the unique structure of the Louisville Twin Study (longitudinal data collected continuously from 1957 to 1999 using the Wechsler Intelligence Scale for Children [WISC], WISC-R, and WISC-III ed.), multilevel analyses revealed between-subjects Flynn Effects-as both decrease in mean scores upon test re-standardization and increase in mean scores across cohorts-as well as within-child Flynn Effects on cognitive growth across age. Overall gains equaled approximately three IQ points per decade. Novel genetically informed analyses suggested that individual sensitivity to the Flynn Effect was moderated by an interplay of genetic and environmental factors.

Flaws in Flynn Effect Research With the Wechsler Scales

Many Flynn effect (FE) studies compare scores across different editions of Wechsler’s IQ tests. When construct changes are introduced by the test developers in the new edition, however, the presumed generational effects are difficult to untangle from changes due to test content. To remove this confound, we use the same edition of Wechsler Intelligence Scale for Children–Fourth Edition (WISC-IV) across an 11-year period. Whereas previous research has reported the FE to be less than half the theoretical rate when comparing WISC-IV with Wechsler Intelligence Scale for Children–Fifth Edition (WISC-V), we find the rate of gain to be nearly identical to Flynn’s prediction when comparing only WISC-IV scores over the same time period. The FE is shown to vary significantly across the domains of cognitive ability, and thus changes to the construct coverage of the WISC-V Full Scale IQ (FSIQ) composite between editions significantly affect FE findings. Implications for future FE research are discussed.

Pediatric epilepsy and comorbid reading disorders, math disorders, or autism spectrum disorders: Impact of epilepsy on cognitive patterns

INTRODUCTION

In pediatric epilepsy, comorbidities are reported to be frequent. The present study focusedon the cognitive patterns of children with isolated epilepsy, children with isolated neurodevelopmental disorders (reading disorders, math disorders, autism spectrum disorders), and children with epilepsy and these neurodevelopmental disorders as comorbidities.

METHODS

Based on two samples of referred children, one with epilepsy, reading disorders, math disorders, or ASDs occurring in "isolation" (n=117) and one with reading disorders, math disorders, and ASDs occurring comorbid with epilepsy (n=171), cognitive patterns were compared. The patterns displayed by verbal and nonverbal abilities from the WISC series were studied with repeated measures ANOVA. Thereafter, an exploratory 2∗3∗2 factorial analysis was done to study the independent contribution of the type of comorbidity and of the presence or absence of epilepsy to the VIQ-PIQ pattern.

RESULTS

In isolated epilepsy, a VIQ>PIQ pattern was found, which was not seen in the other disorders. When epilepsy and another disorder co-occurred, patterns were altered. They resembled partly the pattern seen in isolated epilepsy and partly the pattern seen in the isolated neurodevelopmental disorder. In comorbid reading disorders, the VIQ>PIQ pattern was mitigated; in comorbid math disorders, it was exacerbated. In comorbid ASDs, no clear pattern emerged. In the presence of epilepsy, patterns characteristic of isolated disorders appeared systematically shifted toward relatively lowered performance abilities or relatively spared verbal abilities. The similar "impact" exerted by epilepsy on the patterns of the various conditions suggested shared mechanisms.

Using Score Equating and Measurement Invariance to Examine the Flynn Effect in the Wechsler Adult Intelligence Scale

The Flynn effect (FE; i.e., increase in mean IQ scores over time) is commonly viewed as reflecting population shifts in intelligence, despite the fact that most FE studies have not investigated the assumption of score comparability. Consequently, the extent to which these mean differences in IQ scores reflect population shifts in cognitive abilities versus changes in the instruments used to measure these abilities is unclear. In this study, we used modern psychometric tools to examine the FE. First, we equated raw scores for each common subtest to be on the same scale across instruments. This enabled the combination of scores from all three instruments into one of 13 age groups before converting raw scores into Z scores. Second, using age-based standardized scores for standardization samples, we examined measurement invariance across the second (revised), third, and fourth editions of the Wechsler Adult Intelligence Scale. Results indicate that while scores were equivalent across the third and fourth editions, they were not equivalent across the second and third editions. Results suggest that there is some evidence for an increase in intelligence, but also call into question many published FE findings as presuming the instruments' scores are invariant when this assumption is not warranted.

Assessing the Flynn Effect in the Wechsler Scales

The current study examined the Flynn Effect (i.e., the increase in IQ scores over time) across all editions of the Wechsler Adult Intelligence Scale (WAIS), Wechsler Intelligence Scale for Children (WISC), and Wechsler Preschool and Primary Scale of Intelligence (WPPSI). By reverse engineering the correlation and scale score transformations from each Wechsler edition’s technical manual, we made a mean and covariance matrix using the subtests and age groups that were in common for all editions of a given instrument. The results indicated that when aggregated, there was a FE of 0.44 IQ points/year. This Wechsler instrument used, however, moderates the FE, with the WISC showing the largest FE (0.73 IQ points/year) and the WAIS showing a smallest FE (0.30 IQ points/year). Moreover, this study found that the amount of invariant indicators across instruments and age groups varied substantially, ranging from 51.53% in the WISC for the 7-year-old group to 10.00% in the WPPSI for the 5- and 5.5-year-old age groups. Last, we discuss future direction for FE research based on these results.

Cognitive Tests in Early Childhood

Cognitive assessment of young children contributes to high-stakes decisions because results are often used to determine eligibility for early intervention and special education. Previous reviews of cognitive measures for young children highlighted concerns regarding adequacy of standardization samples, steep item gradients, and insufficient floors for young children functioning at lower levels. The present report extends previous reviews by including measures recently published or revised, nonverbal cognitive assessment tools, and issues specific to assessing bilingual or non-English-speaking children. Sixteen tests were reviewed, including all available measures of cognitive functioning for 2- to 4-year-old children normed in the United States. Test characteristics evaluated included (a) representativeness and recency of standardization data, (b) item bias analysis, (c) psychometric characteristics, and (d) appropriateness for assessing young children with developmental delays and non-English-speaking children. Implications are discussed for clinicians, researchers, and test developers.

Age-related change in Wechsler IQ norms after adjustment for the Flynn effect: estimates from three computational models

A previous study found that the Flynn effect accounts for 85% of the normative difference between 20- and 70-year-olds on subtests of the Wechsler intelligence tests. Adjusting scores for the Flynn effect substantially reduces normative age-group differences, but the appropriate amount of adjustment is uncertain. The present study replicates previous findings and employs two other methods of adjusting for the Flynn effect. Averaged across models, results indicate that the Flynn effect accounts for 76% of normative age-group differences on Wechsler IQ subtests. Flynn-effect adjustment reduces the normative age-related decline in IQ from 4.3 to 1.1 IQ points per decade.

Aumento da inteligência ao longo do tempo: efeito Flynn e suas possíveis causas

O presente trabalho descreve o efeito Flynn, entendido como os ganhos verificados nas medidas de inteligência ao longo do tempo. Para viabilizar a compreensão do efeito, são apresentadas algumas concepções psicométricas sobre a inteligência, sobretudo as que sugerem uma organização hierárquica das capacidades cognitivas, diferenciando fatores mais gerais de fatores mais específicos. O efeito Flynn tende a ser mais consistentemente observado em testes que avaliam a inteligência geral e a inteligência fluida. As possíveis causas explicativas do efeito Flynn são igualmente apresentadas e discutidas, dentre elas: os anos de escolaridade, a nutrição, a complexidade dos ambientes mais atuais, a atitude assertiva para resolver testes e a heterose.

The impact of the Flynn effect on LD diagnoses in special education

Because of the Flynn effect, IQ scores rise as a test norm ages but drop on the introduction of a newly revised test norm. The purpose of the current study was to determine the impact of the Flynn effect on learning disability (LD) diagnoses, the most prevalent special education diagnosis in the United States. Using a longitudinal sample of 875 school children who were initially diagnosed with LD on the Wechsler Intelligence Scale for Children-Revised (WISC-R), children experienced a significant decline in IQ when retested on the third edition of the WISC (WISC-III) compared to peers who were tested on the WISC-R twice. Furthermore, results from logistic regression analyses revealed that the probability of a rediagnosis of LD on reevaluation significantly decreased, in part, because of this decline on the WISC-III. These results are discussed in terms of their implications for both basic research and educational policy.

Standard of practice and Flynn Effect testimony in death penalty cases

The Flynn Effect is a well-established psychometric fact documenting substantial increases in measured intelligence test performance over time. Flynn's (1984) review of the literature established that Americans gain approximately 0.3 points per year or 3 points per decade in measured intelligence. The accurate assessment and interpretation of intellectual functioning becomes critical in death penalty cases that seek to determine whether an individual meets the criteria for intellectual disability and thereby is ineligible for execution under Atkins v. Virginia (2002) . We reviewed the literature on the Flynn Effect and demonstrated how failure to adjust intelligence test scores based on this phenomenon invalidates test scores and may be in violation of the Standards for Educational and Psychological Testing as well as the "Ethical Principles for Psychologists and Code of Conduct." Application of the Flynn Effect and score adjustments for obsolete norms clearly is supported by science and should be implemented by practicing psychologists.

Problems With IQ Gains: The Huge Vocabulary Gap

Despite Kaufman, Raven’s Progressive Matrices and the Wechsler subtest Similarities are tests whose gains call for special explanation. The spread of “scientific spectacles” is the key, but its explanatory potential has been exhausted. Three trends force us to look elsewhere: (a) gains on Wechsler subtests such as Picture Arrangement, (b) gains in developed nations persisting into the 21st century, (c) the growing gap between the active vocabularies of parents and their children.

IQ Scores Should Be Corrected for the Flynn Effect in High-Stakes Decisions

IQ test scores should be corrected for high stakes decisions that employ these assessments, including capital offense cases. If scores are not corrected, then diagnostic standards must change with each generation. Arguments against corrections, based on standards of practice, information present and absent in test manuals, and related issues, ignore expert consensus about the assessment of intellectual disabilities and the acceptance of the Flynn effect in the field. Most psychometric concerns about correction are based on validity studies with small subgroups and do not reflect sufficient effort to estimate the precision of the Flynn estimate. We computed a confidence interval for the Wechsler PIQ across four validity studies that shows a SEM of about 1 around a mean of about 3 points per decade. A meta-analytic weighted mean of the 14 studies in Flynn (2009) is 2.80 (2.50, 3.09), close to Flynn’s (2009) unweighted average (2.99). More psychometric research would be helpful, but this level of precision supports the Flynn adjustment of 3 points per decade.

The Flynn Effect and Its Critics: Rusty Linchpins and “Lookin’ for g and Gf in Some of the Wrong Places”

The consensus of most intelligence scholars is that the Flynn effect (FE) is real, IQ test batteries are now routinely restandardized on a regular basis. A cornerstone in Flynn’s explanation of the FE is his analysis of select Wechsler subtest scores across time. The featured articles by Kaufman and Zhou, Zhu, and Weiss question whether Flynn’s arguments are grounded in the unproven assumption that similarly named Wechsler scores measure the same constructs across editions. Kaufman raises the issue by means of a detailed task analysis of changes in test administration and scoring directions for similarly named tests across different Wechsler editions. The author applauds Zhou et al. for bringing methodological rigor to the comparison of similarly named Wechsler Performance composite scores across time. Unfortunately, both Kaufman and Zhou et al. inadvertently perpetuate some of Flynn’s incorrect interpretations of select Wechsler measures (Similarities and Performance tests) as measures of the novel abstract problem solving that characterizes fluid intelligence (Gf). The author presents empirical Wechsler subtest g-loadings based on seven Wechsler joint- or cross-battery factor analyses (with other cognitive batteries). The results suggest that the extant Wechsler FE data and its system of interpretations, hypotheses, and resultant theory are held together by multiple anchors, a number that, in the words of Kaufman, are “seriously coated in rust.” The author briefly discusses the theory, tools, and technologies that currently exist to place a more reasonable degree of order in the house built by Flynn.

Considerations on the Flynn Effect

Flynn has proposed a grand integrative theory, which he calls “scientific spectacles,” to explain the phenomenon of rising IQ scores across multiple decades known as the Flynn effect (FE). In his theory, he purports that modern society has placed increasing value and emphasis on the application and education of scientific principles—which include abstract fluid reasoning—and this has mirrored larger score increases in the abstract fluid reasoning tasks included as part of most intelligence tests. He highlights huge gains in the Wechsler Similarities subtest over time as one linchpin supporting his theory that fluid reasoning is rising faster than other aspects of intelligence, but further points to large increases in Wechsler performance tasks (i.e., perceptual organization and reasoning) relative to crystallized tasks, and to the many studies of Raven’s Progressive Matrices, which is widely held to be a fairly pure measure of fluid reasoning. As with any new theory of this magnitude, Flynn’s grand proposal has invited numerous criticisms that must now be addressed—and this is as it should be in the spirit of scientific progress. Each of these issues is multilayered and has many legitimate perspectives. The present article attempts to carefully consider each issue and perspective in sequence.

Peeking Inside the “Black Box” of the Flynn Effect: Evidence From Three Wechsler Instruments

This study investigated the Wechsler Performance IQ (PIQ) or Perceptual Reasoning Index (PRI)/ Perceptual Organization Index (POI) change over time and its relation to ability levels. PIQ or PRI/ POI was analyzed because of the known sensitivity of nonverbal scales to the Flynn effect. Scores were analyzed using two methods. First, analysis of covariance was applied to the combination of four representative samples of individuals who were administered the following pairs of Wechsler batteries in counterbalanced order: Wechsler Preschool and Primary Scale of Intelligence—Revised (WPPSI-R) and WPPSI-III ( N = 174), Wechsler Intelligence Scale for Children — Third Edition (WISC-III) and WISC-IV ( N = 239), Wechsler Adult Intelligence Scale—Revised (WAIS-R) and WAIS-III ( N = 191), and WAIS-III and WAIS-IV ( N = 240). Second, equal percentile equating was applied to each of the samples independently. Although the two methods produced different patterns of results, both methods showed some evidence of variation in the magnitude of the Flynn effect across ability levels. These results call into question the practice of adjusting IQs based on an average expected Flynn effect in routine clinical evaluations.

Looking Through Flynn’s Rose-Colored Scientific Spectacles

In the first article of this special issue of the Journal of Psychoeducational Assessment, I critiqued Flynn’s theoretical explanation of the Flynn effect because he depended too heavily on an apparently huge generational gain on the WISC Similarities subtest; I claimed he was comparing apples with oranges because that subtest changed too much when the WISC was first revised. Four sets of esteemed researchers were invited to respond to my article and also to an article by Zhou, Zhu, and Weiss—Flynn, Sternberg, McGrew, and Ceci and Kanaya. Flynn disagrees strongly with my critique of his theory, a theory that posits striking generational shifts from concrete (utilitarian) thinking to a kind of fluid reasoning that Flynn nicknames “scientific spectacles.” In this final article of the special issue, I respond to Flynn’s claims, and also to the points made by the other invited respondents. In addition, I respond to the range of opinions expressed by the scholars who were invited to write an essay on whether or not IQs should be adjusted for the Flynn effect in capital punishment cases (Fletcher et al., Hagan et al., and Reynolds et al.). Ultimately, I disagree with Flynn’s explanation of the Flynn effect, but I agree with his position that IQs should be adjusted for the effect in death penalty cases.

“Apples and Oranges Are Both Round”: Furthering the Discussion on the Flynn Effect

While the magnitude of the Flynn effect is well established (approximately 3 points a decade on the Wechsler scales), the causes behind it are still unknown and hotly debated. Kaufman argues that, because of the administrative and scoring changes that occurred with the introduction of the Wechsler Intelligence Scale for Children—Revised, Flynn’s interpretation of the effect is not appropriate. Although agreeing that these changes account for some aspects of rising IQ, this study questions the impact of these administrative/scoring changes to account for most of the impact, given the heavy documentation of the Flynn effect on multiple IQ tests and norms over time and around the world. The authors also add to the discussion led by Zhou, Zhu, and Weiss by stressing the importance of examining the role of individual differences within the Flynn effect to understand fully the exact nuances and cause(s) of it.

The Flynn Effect: So What?

The Flynn effect probably has multiple causes, and the target essays in this issue have expanded the number of possible causes behind it. This essay deals primarily with a different question: How important is IQ in the current world and should it perhaps be understood also in conjunction with a consideration of some kind of ethical intelligence?