Confirmatory factor analysis of the Wechsler Intelligence Scale for Children--Third Edition in an Australian clinical sample

A confirmatory factor analysis was conducted on the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; D. Wechsler, 1991) with a sample of 579 Australian children referred for assessment because of academic difficulties in the classroom. The children were administered the WISC-III as part of the initial eligibility determination process for funding of special education services. The children were aged between 6 years and 16 years 7 months. One-, two-, three-, and four-factor models were tested. The four-factor model proposed in the WISC-III manual fit the data significantly better than all other models tested.     

Confirmatory factor analysis of the WAIS-IV/WMS-IV

The Wechsler Adult Intelligence Scale-fourth edition (WAIS-IV) and the Wechsler Memory Scale-fourth edition (WMS-IV) were co-developed to be used individually or as a combined battery of tests. The independent factor structure of each of the tests has been identified; however, the combined factor structure has yet to be determined. Confirmatory factor analysis was applied to the WAIS-IV/WMS-IV Adult battery (i.e., age 16-69 years) co-norming sample (n = 900) to test 13 measurement models. The results indicated that two models fit the data equally well. One model is a seven-factor solution without a hierarchical general ability factor: Verbal Comprehension, Perceptual Reasoning, Processing Speed, Auditory Working Memory, Visual Working Memory, Auditory Memory, and Visual Memory. The second model is a five-factor model composed of Verbal Comprehension, Perceptual Reasoning, Processing Speed, Working Memory, and Memory with a hierarchical general ability factor. Interpretative implications for each model are discussed.     

WAIS-IV subtest covariance structure: conceptual and statistical considerations

D. Wechsler (2008b) reported confirmatory factor analyses (CFAs) with standardization data (ages 16-69 years) for 10 core and 5 supplemental subtests from the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV). Analyses of the 15 subtests supported 4 hypothesized oblique factors (Verbal Comprehension, Working Memory, Perceptual Reasoning, and Processing Speed) but also revealed unexplained covariance between Block Design and Visual Puzzles (Perceptual Reasoning subtests). That covariance was not included in the final models. Instead, a path was added from Working Memory to Figure Weights (Perceptual Reasoning subtest) to improve fit and achieve a desired factor pattern. The present research with the same data (N = 1,800) showed that the path from Working Memory to Figure Weights increases the association between Working Memory and Matrix Reasoning. Specifying both paths improves model fit and largely eliminates unexplained covariance between Block Design and Visual Puzzles but with the undesirable consequence that Figure Weights and Matrix Reasoning are equally determined by Perceptual Reasoning and Working Memory. An alternative 4-factor model was proposed that explained theory-implied covariance between Block Design and Visual Puzzles and between Arithmetic and Figure Weights while maintaining compatibility with WAIS-IV Index structure. The proposed model compared favorably with a 5-factor model based on Cattell-Horn-Carroll theory. The present findings emphasize that covariance model comparisons should involve considerations of conceptual coherence and theoretical adherence in addition to statistical fit.     

Performance of children with epilepsy and normal age-matched controls on the WISC-III.

Research findings regarding the effects of childhood epilepsy on general intelligence have produced variable results. The aim of this study was to investigate the effects of epilepsy, age of seizure onset, and Antiepileptic Drugs (AED) on intellectual ability as assessed by the Wechsler Intelligence Scale for Children, 3rd Edition (WISC-III; Wechsler, 1991). This study included children with epilepsy assessed with the WISC-III who achieved either a Full Scale, Verbal Scale, or Performance Scale IQ score >or= 70. A clinical sample of children diagnosed with epilepsy (n = 32) were age- and gender-matched with subjects from the normative standardization sample for the WISC-III, yielding a total sample of 64 subjects. Comparison using a MANOVA revealed significant differences across WISC-III Index standard scores (p = 0.0005) and subtest scaled scores (p = 0.0013), with control participants performing better than epileptic participants. Secondary analyses were also conducted considering monotherapy (n = 14) versus polytherapy (n = 11), and age of seizure onset (<6 years, n = 12; 6 > years, n = 15). MANOVA comparisons revealed no significant differences between groups across WISC-III Index standard scores.     

Replication of the factor structure of the Wechsler Adult Intelligence Scale--Third Edition with a Canadian sample

Exploratory and confirmatory factor analyses of the subtests of the Wechsler Adult Intelligence Scale--Third Edition (WAIS-III; D. Wechsler, 1997b) were conducted on a stratified sample of Canadian adults (n = 718). As was previously demonstrated for the children's version of this scale, the factor model of the American standardization sample was replicated across this Canadian national sample. Results of the factor analyses confirmed the presence of the 4 WAIS-III factors: Verbal Comprehension, Perceptual Organization, Working Memory, and Processing Speed.     

The effects of Wechsler Intelligence Scale for Children-Fourth Edition cognitive abilities on math achievement

This study used structural equation modeling to examine the effect of Stratum III (i.e., general intelligence) and Stratum II (i.e., Comprehension-Knowledge, Fluid Reasoning, Short-Term Memory, Processing Speed, and Visual Processing) factors of the Cattell-Horn-Carroll (CHC) cognitive abilities, as operationalized by the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV; Wechsler, 2003a) subtests, on Quantitative Knowledge, as operationalized by the Wechsler Individual Achievement Test, Second Edition (WIAT-II; Wechsler, 2002) subtests. Participants came from the WISC-IV/WIAT-II linking sample (n=550). We compared models that predicted Quantitative Knowledge using only Stratum III factors, only Stratum II factors, and both Stratum III and Stratum II factors. Results indicated that the model with only the Stratum III factor predicting Quantitative Knowledge best fit the data.     

WISC-IV and WISC-III profiles in children with ADHD

Wechsler Intelligence Scale for Children, 3rd and 4th editions (WISC-III n = 586 and WISC-IV n = 118), profiles were compared for children with ADHD and normal intelligence. Mean Verbal Comprehension Index (VCI) and Perceptual Organization/Perceptual Reasoning Index (POI/PRI) scores were significantly higher than Freedom From Distractibility/Working Memory Index (FDI/WMI) and Processing Speed Index (PSI), and Symbol Search was higher than Coding. FDI/WMI and PSI scores were similar on both tests, but VCI and POI/PRI were higher on the WISC-IV than on the WISC-III. Therefore, index discrepancies were greater for the WISC-IV, suggesting that the WISC-IV might be better than the WISC-III in delineating the strengths and weaknesses of children with ADHD. All children in the WISC-IV sample scored lowest on WMI or PSI, whereas only 88% of the WISC-III children scored lowest on FDI or PSI. Thus, the WISC-IV may be more helpful in diagnosing ADHD than the WISC-III.     

Criterion-related bias with the guide to the assessment of test-session behavior for the WISC-III and WIAT: Possible race/ethnicity, gender, and SES effects

Using the Guide to the Assessment of Test-Session Behavior for the WISC-III and WIAT (GATSB), Anglo examiners recorded test observations for 969 children between the ages of 6 and 16 years. The children came from the standardization and validity-study samples of GATSB ratings completed with the Wechsler Intelligence Scale-Third Edition (WISC-III) (Wechsler, 1991). The sample differed by race (Anglo, black, Latino), socioeconomic status (SES) (high, middle, low), and gender. GATSB ratings and WISC-III Verbal, Performance, and Full Scale IQs were compared. Correlations between the GATSB and WISC-III were generally moderate (average R = -.27). Children who exhibited higher levels of avoidance, inattentiveness, and uncooperative behaviors while being tested tended to exhibit lower WISC-III scores. This pattern held true for Anglos, blacks, and Latinos; for girls and boys; and for those from high-, middle-, and low-SES homes. Evidence was generally absent that Anglo examiners display bias in black-Anglo, gender, or SES comparisons. However, consistent differences were noted between Latino and Anglo children. Examiners tended to rate Latinos as displaying better test behaviors than Anglos when children's IQs were below average, but comparable when IQs were average and above. Thus, the GATSB generally displayed similar intrasession validities for children who differ by race/ethnicity, gender, and SES.     

Generalizability of WISC-IV index and subtest score profiles in children with traumatic brain injury

The Wechsler Intelligence Scale for Children, 4th edition (WISC-IV) is often used to assess children with traumatic brain injury (TBI); although limited information is available regarding its psychometric properties in these children. Two recent reports suggest that the Perceptual Reasoning Index is not uniquely sensitive to TBI, which differs from the Perceptual Organization Index of the WISC-III. The current study examined WISC-IV profiles in two independently gathered samples of children with TBI. Examination of profiles indicated similarities between the current findings and those reported in other studies, in that the greatest deficits were present on the Processing Speed Index and its component subtests of Coding and Symbol Search, while the Perceptual Reasoning index score was comparable to the Verbal Comprehension Index. Also, no significant index or subtest score differences were present when the current sample was compared to the children with TBI reported by Allen, Thaler, Donohue and Mayfield (2010 ). The present findings are consistent with two prior studies of the WISC-IV in children with TBI, providing additional evidence for profile differences between the WISC-III and WISC-IV. The results also suggest that WISC-IV profiles reported in prior studies are generalizable across TBI samples and study sites.     

Validity of a short form of the WISC-III in children with traumatic head injury

The concurrent, construct, and criterion validities of Donders' (in press) short form of the Wechsler Intelligence Scale for Children - Third Edition (WISC-III) were evaluated in a sample of 171 children with traumatic head injury (THI). Correlations between the short-form deviation quotients and their full-length counterparts were statistically significant. Confirmatory factor analysis revealed that a four-factor model (composed of Verbal Comprehension, Perceptual Organization, Freedom from Distractibility, and Processing Speed) fit the data relatively well. The short-form deviation quotients also had statistically significant correlations with length of coma. It is concluded that this short form is an accurate and valid alternative to the full-length WISC-III in children with THI.     

Factor structure of the Wechsler Adult Intelligence Scale-III in schizophrenia

This report examines and compares the factor structure of the new edition of the Wechsler Adult Intelligence Scale (WAIS-III) in a sample of chronic schizophrenia and schizoaffective disorder outpatients (n = 120) and an age-matched sample of individuals drawn from the WAIS-III standardization sample (n = 200). Exploratory and confirmatory factor analyses similar to those reported by the developers of the scale suggested that a model of WAIS-III performance with correlated factors for verbal comprehension, perceptual organization, working memory, and processing speed fit the data from the schizophrenia sample as well as it fit the nonclinical comparison sample and fit the data from both samples better than alternative models.     

Factor analysis of the Wechsler adult intelligence scale-revised (WAIS-R): An examination of the standardization sample

Orthogonal and oblique factor analyses were performed using the Wechsler Adult Intelligence Scale-Revised (WAIS-R) standardization sample (Wechsler, 1981). Using objective criteria, it was decided to retain two factors. Evidence for a strong general intelligence (g) factor was found from both the orthogonal and oblique rotations. Whereas the verbal IQ provided an acceptable estimate of the Verbal Comprehension factor, a purer measure was found in the form of a Verbal Comprehension Deviation Quotient containing only the Information, Vocabulary, Comprehension, and Similarities subtests. The performance IQ was found to be an inadequate measure of the Perceptual Organization factor. A Perceptual Organization Deviation Quotient, containing only the Block Design and Object Assembly subtests, was recommended as an effective alternative. Analysis of the variance components for each subtest at every age level revealed that a substantial proportion of subtests at a wide range of age levels evidence either high or intermediate levels of specific variance. These results are discussed in terms of interpreting individual subtest scores and patterns. Each of the study's major findings are compared with prior work done with the Wechsler Adult Intelligence Scale (WAIS) (Wechsler, 1955).     

Factor structure of the Norwegian version of the WAIS-III in a clinical sample: the arithmetic problem

Confirmatory Factor Analyses (CFA) of the Wechsler Adult Intelligence Scale-III (WAIS-III) lend partial support to the four-factor model proposed in the test manual. However, the Arithmetic subtest has been especially difficult to allocate to one factor. Using the new Norwegian WAIS-III version, we tested factor models differing in the number of factors and in the placement of the Arithmetic subtest in a mixed clinical sample (n = 272). Only the four-factor solutions had adequate goodness-of-fit values. Allowing Arithmetic to load on both the Verbal Comprehension and Working Memory factors provided a more parsimonious solution compared to considering the subtest only as a measure of Working Memory. Effects of education were particularly high for both the Verbal Comprehension tests and Arithmetic.     

Discriminant validity of test observations for children with Attention Deficit/Hyperactivity

This paper investigates the discriminant validity of test-session behaviors by comparing whether the observations of children with Attention-Deficit/Hyperactivity Disorder (ADHD) differed from those of unclassified controls. Test-taking behaviors were evaluated according to the Guide to the Assessment of Test Session Behavior for the WISC-III and WIAT (GATSB) (Glutting & Oakland, 1993) following administrations of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) (Wechsler, 1991). Two groups were compared: an ADHD cohort (n = 49) and children from the GATSB standardization sample (n = 49) matched on the background characteristics of age, race, gender, parent educational attainment, and overall cognitive ability. A multivariate, two-group discriminant function analysis was used to compare groups. Results showed children with ADHD could be differentiated, Wilks &clgr; = .632, F = 18.96, df (3, 94]) p < .001). A classification analysis was used to evaluate the practical utility of the discrimination. The overall hit rate was 80.6% (p < .05), thereby adding to the overall validity of results. Findings suggest that in the course of one-to-one clinical assessments, standardized ratings of children's test behaviors provide useful information about the relative severity of children's inattentive, avoidant, and uncooperative dispositions, and that these factors can affect the magnitude of children's IQs.     

Factor analysis of the WISC-R and the Adaptive Behavior Scale-School Edition for a referral sample

The purpose of this study was to determine if a common factor structure was evident in the Wechsler Intelligence Scale for Children-Revised (WISC-R) and the Adaptive Behavior Scale-School Edition (ABS-SE) for a sample of 171 children referred for evaluation of learning and behavior problems. The WISC-R subtests (excluding Mazes) and the ABS-SE factor domain scores (Personal Self-Sufficiency, Community Self-Sufficiency, Personal-Social Responsibility, Social Adjustment, and Personal Adjustment) were subjected to an exploratory principal-components factor analysis with varimax rotation. ANOVAs were conducted on each of the derived factors to determine race and sex effects. The results indicated no common factor structure in the instruments, the Verbal Comprehension, Perceptual Organization, Independent Functioning, Maladaptive Behavior, and Freedom From Distractibility factors being extracted. The derived factors were very similar to those identified in standardization data and other studies. Perceptual Organization and Social Adjustment showed sex and race effects, respectively, although each model accounted for only about 7% of the variance.     

Confirmatory factor analyses of the WAIS-III standardization data

Confirmatory factor analyses with the standardization data of the Wechsler Adult Intelligence Scale-Third Edition (Wechsler, 1997a) compared 6 models with 1 to 4 factors for 11- and 13-subtest versions of the test. Three factors usually fit the data better than 2 factors, but 2-factor models were more parsimonious. A 2-factor model with a Verbal Comprehension factor (Vocabulary, Similarities, Information, and Comprehension) was as good as and sometimes better than the 2-factor model defined by the traditional separation of Verbal and Performance subtests. For 3-factor models, alternative specifications of processing speed subtests on either the Perceptual Organization or Freedom From Distractibility factor were comparable, and specifying a 4th factor for Digit Symbol and Symbol Search had little advantage in comparison with 3-factor models with correlated errors for the 2 subtests.     

Beery-Buktenica Developmental Test of Visual-Motor Integration performance in children with traumatic brain injury and attention-deficit/hyperactivity disorder

Evaluation of visuoconstructional abilities is a common part of clinical neuropsychological assessment, and the Beery-Buktenica Developmental Test of Visual-Motor Integration (VMI; K. E. Beery & N. A. Beery, 2004) is often used for this purpose. However, few studies have examined its psychometric properties when used to assess children and adolescents with traumatic brain injury (TBI) or attention-deficit/hyperactivity disorder (ADHD), even though these are among the most common acquired and neurodevelopmental forms of brain dysfunction in children. This study examined the validity of VMI scores in 123 children with TBI and 65 with ADHD. The TBI and ADHD groups performed significantly worse than the standardization sample, obtaining VMI mean scores of 87.2 (SD = 13.7) and 93.5 (SD = 11.27). Previous research has noted decrements in visuoconstructional abilities in TBI but relative sparing in ADHD. To examine the criterion validity of VMI scores, the authors therefore compared these 2 groups. As anticipated, the TBI group performed significantly worse than the ADHD group, but receiver operator characteristic analysis indicated that VMI scores were poor at discriminating between groups. Nonetheless, convergent validity evidence supported interpretation of VMI scores as measuring perceptual organization in both groups. In particular, principal components analysis indicated that VMI total scores loaded with perceptual organization tests from the Wechsler Intelligence Scale for Children, 3rd ed. (WISC-III; D. Wechsler, 1997), and its highest correlation was with the WISC-III Perceptual Organization Index. Also, the VMI correlated significantly with the Grooved Pegboard test for the group with TBI. These findings suggest that VMI scores are sensitive to visuoconstructional and motor deficits in children with developmental and acquired brain dysfunction.     

Factorial similarity of the WISC-R for Anglos and Chicanos referred for psychological services

Two- and three-factor principal factor solutions to the WISC-R (Wechsler, 1974) were compared across race for referred Anglo and Chicano children. Additional comparisons of these factor solutions were made with those for normal Anglo, Chicano, Black, and Papago students (Reschly, 1978, Note 1) and the WISC-R standardization sample (Wechsler, 1974). Substantial congruence occurred across race for both the two- and three-factor solutions, though the two-factor solution was clearly most appropriate for the present sample.     

Prototypicality of responses of autistic,language disordered,and normal children in a word fluency task

This article describes an example of making pediatric neuropsychological assessments more time-efficient. Empirical support, including new data, for the utilization of an eight-subtest short form of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; Wechsler, 1991) is reviewed. It is concluded that this short form of the WISC-III is a valid substitute for the complete version under most clinical circumstances, allowing the practitioner to expand on interview, history or more specific neuropsychological tests without adding financial or time burdens to the evaluation.     

Structure of the Wechsler Intelligence Scale for Children--Fourth Edition among a national sample of referred students

The structure of the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV; D. Wechsler, 2003a) was analyzed via confirmatory factor analysis among a national sample of 355 students referred for psychoeducational evaluation by 93 school psychologists from 35 states. The structure of the WISC-IV core battery was best represented by four first-order factors as per D. Wechsler (2003b), plus a general intelligence factor in a direct hierarchical model. The general factor was the predominate source of variation among WISC-IV subtests, accounting for 48% of the total variance and 75% of the common variance. The largest 1st-order factor, Processing Speed, only accounted for 6.1% total and 9.5% common variance. Given these explanatory contributions, recommendations favoring interpretation of the 1st-order factor scores over the general intelligence score appear to be misguided.