Seemingly anomalous full scale IQ scores on the WAIS-III and the WISC-III

The Canadian and American WISC-III and the American WAIS-III standardization data were used to investigate the prevalence of “seemingly anomalous” Full Scale IQ (FSIQ) scores for all possible Verbal and Performance sums of scale score combinations. It was found that 6% of FSIQ scores in these three samples were seemingly anomalous (i.e., fell outside of their associated VIQ/PIQ intervals). Interestingly, the anomalous FSIQ scores were more prevalent at the extremes of the FSIQ distribution, and did not occur when the VIQ/PIQ interval was greater than 12. Additionally, anomalous FSIQ scores were generally further from the center of the FSIQ distribution than were the associated VIQ and PIQ scores. Also, when the VIQ/PIQ interval contained FSIQ (the non-anomalous case), FSIQ tended to be located distally in the half-segment of the VIQ/PIQ interval furthest from the center of the FSIQ distribution. A statistical explanation for the findings is provided. Portions of this paper were presented March 3, 2000 at the 14th Annual Joseph R. Royce Research Conference, Department of Psychology, University of Alberta, Edmonton, Alberta. An erratum to this article is available at .     

Seemingly anomalous full scale IQ scores on the WAIS-III and the WISC-III

The Canadian and American WISC-III and the American WAIS-III standardization data were used to investigate the prevalence of “seemingly anomalous” Full Scale IQ (FSIQ) scores for all possible Verbal and Performance sums of scale score combinations. It was found that 6% of FSIQ scores in these three samples were seemingly anomalous (i.e., fell outside of their associated VIQ/PIQ intervals). Interestingly, the anomalous FSIQ scores were more prevalent at the extremes of the FSIQ distribution, and did not occur when the VIQ/PIQ interval was greater than 12. Additionally, anomalous FSIQ scores were generally further from the center of the FSIQ distribution than were the associated VIQ and PIQ scores. Also, when the VIQ/PIQ interval contained FSIQ (the non-anomalous case), FSIQ tended to be located distally in the half-segment of the VIQ/PIQ interval furthest from the center of the FSIQ distribution. A statistical explanation for the findings is provided. Portions of this paper were presented March 3, 2000 at the 14th Annual Joseph R. Royce Research Conference, Department of Psychology, University of Alberta, Edmonton, Alberta. An erratum to this article is available at .     

Meta-Analysis of Intelligence Quotient (IQ) in Obsessive-Compulsive Disorder

Obsessive compulsive disorder (OCD) is associated with a moderate degree of underperformance on cognitive tests, including deficient processing speed. However, despite little research focusing on Intelligence Quotient (IQ) in OCD, it has long been speculated that the disorder is associated with elevated intellectual capacity. The present meta-analytic study was, therefore, conducted to quantitatively summarize the literature on IQ in OCD systematically. We identified 98 studies containing IQ data among individuals with OCD and non-psychiatric comparison groups, and computed 108 effect sizes for Verbal IQ (VIQ, n = 55), Performance IQ (PIQ, n = 13), and Full Scale IQ (FSIQ, n = 40). Across studies, small effect sizes were found for FSIQ and VIQ, and a moderate effect size for PIQ, exemplifying reduced IQ in OCD. However, mean IQ scores across OCD samples were in the normative range. Moderator analyses revealed no significant moderating effect across clinical and demographic indices. We conclude that, although lower than controls, OCD is associated with normative FSIQ and VIQ, and relatively lowered PIQ. These results are discussed in light of neuropsychological research in OCD, and particularly the putative impact of reduced processing speed in this population. Recommendations for utilization of IQ tests in OCD, and directions for future studies are offered.     

Scoring reliability on the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III)

Nineteen psychologists and 19 graduate students scored two Wechsler Adult Intelligence Scale-Third Edition patient protocols. Mean IQs and indexes were similar across groups, but the ranges for Verbal IQ (VIQ), Performance IQ (PIQ), and Full Scale IQ (FSIQ) on one protocol were 25, 22, and 11 points, respectively. For both protocols taken together, percentages of agreement with the "actual" IQs for psychologists were only 26.3 for VIQ, 36.8 for PIQ, and 42.1 for FSIQ. For students, percentages were 15.8 for VIQ, 23.7 for PIQ, and 31.6 for FSIQ. The percentages of FSIQs that fell within +/- 1 standard error of measurement of the actual IQs were 89.5 for psychologists and 76.3 for students. Scoring error also had a negative impact on index scores. Both groups were confident about their scoring accuracy.     

The factorial similarity of the WISC-R performance Scale in deaf and hearing samples

Wechsler Intelligence Scale for Children—Revised (WISC-R) Performance Scale metrics and subtest factor loadings, derived separately from deaf (N = 1228) and hearing (N = 2200) samples, are practically identical. Small mean differences are probably attributable to the higher incidence of brain damage among deaf children. In addition to demonstrating the absence of construct bias in WISC-R Performance IQ (PIQ) measurement for deaf children, the results contradict theories which propose linguistic bias as the cause of the white-black difference in Performance IQ. Spearman's hypothesis that white-black mental test differences are primarily a difference in g received significant support. The results indicate that cognition, as measured by PIQ, is virtually independent of language acquisition.     

Graduate student WAIS-III scoring accuracy is a function of full scale IQ and complexity of examiner tasks

Research on the Wechsler Adult Intelligence Scale-Revised and Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) suggests that practicing clinical psychologists and graduate students make item-level scoring errors that affect IQ, index, and subtest scores. Studies have been limited in that Full-Scale IQ (FSIQ) and examiner administration, recording, and scoring tasks have not been systematically varied. In this study, graduate student participants score a high (FSIQ = 112) and low (FSIQ = 85) IQ record form in one of two stimulus conditions: digitized film clips (N = 13) or partially completed record forms (N = 11). Results demonstrate that examiners are less accurate in the high IQ condition, and that recording examinee responses from scoring video clips results in more scoring errors. Obtained FSIQs are significantly higher than criterion IQ scores in the high IQ condition (8.46 for video condition, 2.55 for record form condition). Self-reported proficiency in WAIS-III administration and scoring is positively related to number of scoring errors.     

Validity of the Wechsler abbreviated scale of intelligence and other very short forms of estimating intellectual functioning

Performance on the Wechsler Adult Intelligence Scale-III (WAIS-III) was compared to performance on the Wechsler Abbreviated Scale of Intelligence (WASI), as well as short form estimations of intellectual functioning derived from WAIS-III performance, in a mixed clinical sample of 72 participants. The WASI verbal IQ (VIQ) score was significantly higher than the WAIS-III VIQ, whereas performance IQ (PIQ) estimates all differed from actual WAIS-III PIQ and full scale IQ (FSIQ). Correlations of WAIS-III scores with WASI scores were consistently lower than were correlations between the WASI-III and all other short forms. Although maintaining administration times of 15 minutesfor a two-subtest FSIQ and 30 minutes for a four-subtest FSIQ, the WASI did not consistently demonstrate desirable accuracy in predicting scores obtained from the WAIS-III. The results suggest that clinicians should use the WASI cautiously if at all, especially when accurate estimates of individuals' WAIS-III results are needed.     

The validity of the general ability measure for adults: comparison with WAIS-R IQ scores in a sample of college students with academic difficulties

The present study investigated the validity of the General Ability Measure for Adults (GAMA) by comparing it to the WAIS-R using a sample of 80 college students reporting learning difficulties. Results indicated that the mean GAMA IQ score did not deviate significantly from the mean WAIS-R IQ scores. The GAMA Full Scale IQ correlated significantly with the WAIS-R PIQ, VIQ, and FSIQ scores. However, the obtained correlation coefficient for the GAMA and WAIS-R PIQ significantly differed from the observed correlation coefficient between the GAMA and WAIS-R VIQ, suggesting that the GAMA was more clearly associated with perceptual skills than verbal abilities. When the correlation coefficients between the GAMA and WAIS-R scores were corrected for the effects of range restriction, the correlation coefficients increased, yet demonstrated the same pattern (e.g., GAMA/PIQ,.69; GAMA/VIQ,.36; GAMA/FSIQ,.60). The GAMA s accuracy in predicting individual student performance on the WAIS-R FSIQ also was examined.     

Dyadic short forms of the Wechsler Adult Intelligence Scale-III

Various short forms of the Wechsler Adult Intelligence Scale (WAIS)/WAIS-R have been developed to obtain estimates of overall intellectual level, although little research of WAIS-III short forms has been published to date. Full Scale IQ (FSIQ) estimatesfromfour WAIS-III dyadic short forms were obtained by entering selected subtest scores from a mixed neurologic/ psychiatric sample (n = 196) into regression equations. Results were cross validated on a second sample (n = 57). Within both samples, WAIS-III FSIQ scores were highly correlated (r = .90-.92, p < .001) with estimated FSIQ scores. Estimated FSIQ fell within 5 points of actual FSIQ in 49% to 74% of cross-validation cases and within 10 points of actual FSIQ in 81% to 93% of the sample. Comparable to findings from previous short-form investigations, actual and estimated FSIQ classification levels agreed in 46% to 67% of cases in the cross-validation sample. These dyadic WAIS-III forms appear appropriate for obtaining gross estimates of FSIQ in similar populations, although caution is recommended in interpreting estimated IQ scores.     

School achievement strongly predicts midlife IQ

The relationship between measures of IQ and standardized school achievement tests is well established at around r ≈ 0.5 when the two are measured in close proximity. The current paper examined the stability of this correlation when comparing elementary school achievement (grades 3–8) and midlife IQ. Iowa Adoption Study participants who had standardized school achievement measures (ITBS) on file were given the WAIS-III. Mean age at IQ testing was 44.01 years (SD 6.65 years). The correlation between school achievement and WAIS-III FSIQ was r = 0.64, suggesting substantial life span stability in this relationship. Furthermore, elementary school achievement was substantially correlated with occupational status and household income at midlife. These findings suggest that standardized school achievement data is a useful measure of premorbid IQ.     

Prereading skills of very-low-birth-weight prematurely born Finnish children

Our objective was to study the prereading skills of very-low-birth-weight (VLBW; ≤ 1500 g) prematurely born children at the age of five years. A regional cohort of 89 VLBW children and 152 full-term (FT) born children was assessed for letter knowledge, phonological processing, and speeded naming. Full-scale IQ (FSIQ) was assessed using a short version of WPPSI-R. The associations of parental and neonatal factors, and FSIQ with prereading skills were assessed. VLBW group had poorer prereading skills, and there were more VLBW children at-risk (performing < ?1 SD) compared to FT children in phonological processing (23% vs. 9%, p = .002), letter knowledge (27% vs. 14%, p = .017), and the accuracy of speeded naming (26% vs. 13%, p = .020). VLBW children had lower average FSIQ and Performance IQ (both comparisons p < .001) than FT controls, but Verbal IQ did not differ. When FSIQ was used as a covariate, VLBW children did not differ from the FT group in prereading skills indicating that they are at risk for more global developmental problems. Lower parental level of education as well as parent's reading problems were negatively associated with VLBW children's prereading skills. Positively, about 75% of VLBW children performed within the normal range in each individual prereading skill.     

Beery VMI performance in autism spectrum disorder

Few studies have examined the visuomotor integration (VMI) abilities of individuals with autism spectrum disorder (ASD). An all-male sample consisting of 56 ASD participants (ages 3–23 years) and 36 typically developing (TD) participants (ages 4–26 years) completed the Beery-Buktenica Developmental Test of Visual-Motor Integration (Beery VMI) as part of a larger neuropsychological battery. Participants were also administered standardized measures of intellectual functioning and the Social Responsiveness Scale (SRS), which assesses autism and autism-like traits. The ASD group performed significantly lower on the Beery VMI and on all IQ measures compared to the TD group. VMI performance was significantly correlated with full scale IQ (FSIQ), performance IQ (PIQ), and verbal IQ (VIQ) in the TD group only. However, when FSIQ was taken into account, no significant Beery VMI differences between groups were observed. Only one TD participant scored 1.5 standard deviations (SDs) below the Beery VMI normative sample mean, in comparison to 21% of the ASD sample. As expected, the ASD group was rated as having significantly higher levels of social impairment on the SRS compared to the TD group across all major domains. However, level of functioning on the SRS was not associated with Berry VMI performance. These findings demonstrate that a substantial number of individuals with ASD experience difficulties compared to TD in performing VMI-related tasks, and that VMI is likely affected by general cognitive ability. The fact that lowered Beery VMI performance occurred only within a subset of individuals with ASD and did not correlate with SRS would indicate that visuomotor deficits are not a core feature of ASD, even though they present at a higher rate of impairment than observed in TD participants.     

WISC-R Subtest But No Overall VIQ–PIQ Difference in Dutch Children with PDD-NOS

VIQ–PIQ differences have been studied in children with autism and Asperger syndrome but have not been studied in a separate group of children with PDD-NO, although, PDD-NOS has a much higher prevalence rate than autism and deficits in communication and social interaction are severe. The Wechsler Intelligence Scale for Children-Revised (WISC-R) was administered to 100 children, aged 6–12 years, with PDD-NOS (n = 76), autism (n = 13), and Asperger syndrome (n = 11). PDD-NOS was diagnosed using explicit research criteria. No overall differences between VIQ and PIQ were found in PDD-NOS and autism. Peaks in the subtest scores on Information, Similarities, Picture Arrangement, and Mazes, and troughs in the subtest scores on Comprehension, Digit Span, and Coding were demonstrated in children with PDD-NOS. Their score on the Freedom from Distractibility factor was lower than the scores on the Verbal Comprehension factor and the Perceptual Organization factor. Children with PDD-NOS seemed to have a similar VIQ–PIQ profile as children with autism, and on the subtest level children with PDD-NOS showed some similarities to children with Asperger syndrome or autism. It was not possible to distinguish PDD-NOS from autism or Asperger syndrome by using IQ scores.     

Test of the definition of learning disability based on the difference between IQ and achievement

A learning disability is commonly defined as a discrepancy between IQ and achievement. This has been criticized for identifying too many children as having a learning disability who have high IQs and average academic achievement. Such overidentification as actually occurred was assessed in 473 referred children (8-16 years, M= 10, SD=2) with normal intelligence. Learning disability was defined as a significant discrepancy (p<.05) between predicted and obtained achievement in reading, mathematics, or written expression on the Wechsler Individual Achievement Test. Predicted achievement was based on the child's WISC-III Full Scale IQ. Overidentification was considered to occur when a child scored at or above age level in reading, mathematics, and writing but still had a significant discrepancy between predicted and obtained achievement by virtue of a high IQ. Learning disability was diagnosed in 312 (66%) of the children. There was no overidentification because all children had one or more WIAT scores below the normative level for their age, i.e., < 100. Further, only 7% of the children were identified with a learning disability based on a WIAT score in the 90s. These children had a mean IQ of 123 and were rated by their teachers and parents as having learning problems.     

Test Review: Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV)

Objective: Evaluate neuropsychological functioning in children with non-syndromic cleft of the lip and/or palate (NSCL/P) through profile variance within type of cleft and comparisons to controls.

Methods: Children ages 7 to 17 years participated; 66 had a diagnosis of NSCL/P and 87 were healthy controls. Neuropsychological tests of language, visual-perceptual, executive functioning, and memory skills were administered. Between- and within-group differences were assessed.

Results: Within cleft types, children with NSCLP had an even profile with equal Verbal and Performance IQ (VIQ and PIQ, respectively). Children with non-syndromic cleft palate only (NSCP) had significantly lower VIQ than PIQ, while children with non-syndromic cleft lip only (NSCL) showed a nonsignificant trend for higher VIQ than PIQ. Overall, subjects with NSCL/P performed lower on measures of expressive language and verbal memory than controls.

Conclusions: While deficits in verbal and memory skills for children with NSCL/P remain apparent, there is still uncertainty around the possible influence of cleft type on the pattern of deficits.     

Seemingly Anomalous WISC-IV Full Scale IQ Scores in the American and Canadian Standardization Samples

The American and Canadian standardization samples for the fourth edition of the Wechsler Intelligence Scale for Children were used to ascertain the prevalence of “seemingly anomalous” Full Scale IQ (FSIQ) scores for all possible sums of scaled scores combinations of the Verbal Comprehension Index, Perceptual Reasoning Index, Working Memory Index, and Processing Speed Index. About 1% of FSIQ scores in both samples were anomalous (that is, fell outside the range of the four indices). Interestingly, the prevalence of anomalous scores was higher at the extremes of the FSIQ distribution. Moreover, anomalous FSIQ scores occurring above or below the mean of the FSIQ distribution (that is, 100) were larger or smaller, respectively, than any of the four indices. Furthermore, if the range of the four indices did contain the FSIQ (the non-anomalous case), when the FSIQ was below or above 100 it tended to be located distally in the half-segment of the range furthest below or above 100, respectively. A non-technical intuitive analogy from Olympic sports and a statistical explanation for the findings are provided. Important implications for practitioners are also presented. Portions of this paper were presented March 17, 2006 at the 20th annual Joseph R. Royce Research Conference, Department of Psychology, University of Alberta, Edmonton, Alberta.     

Seemingly Anomalous WISC-IV Full Scale IQ Scores in the American and Canadian Standardization Samples

The American and Canadian standardization samples for the fourth edition of the Wechsler Intelligence Scale for Children were used to ascertain the prevalence of “seemingly anomalous” Full Scale IQ (FSIQ) scores for all possible sums of scaled scores combinations of the Verbal Comprehension Index, Perceptual Reasoning Index, Working Memory Index, and Processing Speed Index. About 1% of FSIQ scores in both samples were anomalous (that is, fell outside the range of the four indices). Interestingly, the prevalence of anomalous scores was higher at the extremes of the FSIQ distribution. Moreover, anomalous FSIQ scores occurring above or below the mean of the FSIQ distribution (that is, 100) were larger or smaller, respectively, than any of the four indices. Furthermore, if the range of the four indices did contain the FSIQ (the non-anomalous case), when the FSIQ was below or above 100 it tended to be located distally in the half-segment of the range furthest below or above 100, respectively. A non-technical intuitive analogy from Olympic sports and a statistical explanation for the findings are provided. Important implications for practitioners are also presented. Portions of this paper were presented March 17, 2006 at the 20th annual Joseph R. Royce Research Conference, Department of Psychology, University of Alberta, Edmonton, Alberta.     

Verbal–spatial IQ discrepancies impact brain activation associated with the resolution of cognitive conflict in children and adolescents

Verbal–spatial discrepancies are common in healthy individuals and in those with neurodevelopmental disorders associated with cognitive control deficits including: Autism Spectrum Disorder, Non‐Verbal Learning Disability, Fragile X, 22q11 deletion, and Turner Syndrome. Previous data from healthy individuals suggest that the magnitude of the difference between verbal IQ (VIQ) and performance IQ (PIQ) scores (the VIQ>PIQ discrepancy) is associated with reduced thickness in frontal and parietal cortices (inferior frontal, anterior cingulate, inferior parietal lobule, and supramarginal gyrus) that support cognitive control. Unknown is whether the VIQ>PIQ discrepancy is associated with functional deficits in these areas in healthy or ill children and adolescents. We assessed the effects of the VIQ>PIQ discrepancy on fMRI BOLD response during the resolution of cognitive conflict in 55 healthy children and adolescents during performance of a Simon Spatial Incompatibility task. As the magnitude of the VIQ>PIQ discrepancy increased, activation of fronto‐striatal, limbic, and temporal regions decreased during conflict resolution (p < .05, corrected). In exploratory analyses, the VIQ>PIQ discrepancy was associated with reduced functional connectivity from right inferior frontal gyrus to right thalamus and increased functional connectivity to right supramarginal gyrus (ps < .03, uncorrected). The VIQ>PIQ discrepancy may be an important aspect of an individual's cognitive profile and likely contributes to, or is associated with, deficient cognitive control processes characteristic of many childhood disorders.     

On the heritability of inspection time and its covariance with IQ: a twin study

Using the classical twin design, this study investigates the influence of genetic factors on the large phenotypic variance in inspection time (IT), and whether the well established IT–IQ association can be explained by a common genetic factor. Three hundred ninety pairs of twins (184 monozygotic, MZ; 206 dizygotic, DZ) with a mean age of 16 years participated, and 49 pairs returned approximately 3 months later for retesting. As in many IT studies, the pi figure stimulus was used and IT was estimated from the cumulative normal ogive. IT ranged from 39.4 to 774.1 ms (159±110.1 ms) with faster ITs (by an average of 26.9 ms) found in the retest session from which a reliability of .69 was estimated. Full-scale IQ (FIQ) was assessed by the Multidimensional Aptitude Battery (MAB) and ranged from 79 to 145 (111±13). The phenotypic association between IT and FIQ was confirmed (−.35) and bivariate results showed that a common genetic factor accounted for 36% of the variance in IT and 32% of the variance in FIQ. The maximum likelihood estimate of the genetic correlation was −.63. When performance and verbal IQ (PIQ & VIQ) were analysed with IT, a stronger phenotypic and genetic relationship was found between PIQ and IT than with VIQ. A large part of the IT variance (64%) was accounted for by a unique environmental factor. Further genetic factors were needed to explain the remaining variance in IQ with a small component of unique environmental variance present. The separability of a shared genetic factor influencing IT and IQ from the total genetic variance in IQ suggests that IT affects a specific subcomponent of intelligence rather than a generalised efficiency.     

Wechsler performance IQ deficit in depressed children

The original analysis of data on 100 consecutive school age children referred for evaluation of school difficulties showed no differences in IQ among the children with depression and those without depression. Reanalysis of those data shows that a significant number of the depressed children (but not the nondepressed children) have a 15-IQ point Wechsler Performance IQ deficit. This supports the contention that a major subgroup of depressed individuals have right cerebral-hemisphere dysfunction.