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.     

Orthogonal higher order structure and confirmatory factor analysis of the French Wechsler Adult Intelligence Scale (WAIS-III)

According to the most widely accepted Cattell-Horn-Carroll (CHC) model of intelligence measurement, each subtest score of the Wechsler Intelligence Scale for Adults (3rd ed.; WAIS-III) should reflect both 1st- and 2nd-order factors (i.e., 4 or 5 broad abilities and 1 general factor). To disentangle the contribution of each factor, we applied a Schmid-Leiman orthogonalization transformation (SLT) to the standardization data published in the French technical manual for the WAIS-III. Results showed that the general factor accounted for 63% of the common variance and that the specific contributions of the 1st-order factors were weak (4.7%-15.9%). We also addressed this issue by using confirmatory factor analysis. Results indicated that the bifactor model (with 1st-order group and general factors) better fit the data than did the traditional higher order structure. Models based on the CHC framework were also tested. Results indicated that a higher order CHC model showed a better fit than did the classical 4-factor model; however, the WAIS bifactor structure was the most adequate. We recommend that users do not discount the Full Scale IQ when interpreting the index scores of the WAIS-III because the general factor accounts for the bulk of the common variance in the French WAIS-III. The 4 index scores cannot be considered to reflect only broad ability because they include a strong contribution of the general factor.     

Higher Order Factor Structure of the WISC-IV in a Clinical Neuropsychological Sample

A confirmatory factor analysis was conducted examining the higher order factor structure of the WISC-IV scores for 344 children who participated in neuropsychological evaluations at a large children's hospital. The WISC-IV factor structure mirrored that of the standardization sample. The second order general intelligence factor (g) accounted for the largest proportion of variance in the first-order latent factors and in the individual subtests, especially for the working memory index. The first-order processing speed factor exhibited the most unique variance beyond the influence of g. The results suggest that clinicians should not ignore the contribution of g when interpreting the first-order factors.     

Measurement invariance of WISC-IV across normative and clinical samples

Measurement invariance of the WISC-IV second-order factorial structure between normative and clinical samples was investigated using WISC-IV core subtests and a total of 1100 children aged 6-16. Multi-group higher order analysis of mean and covariance structure (MG-MACS) models were used to analyze these data. Results supported measurement invariance. Only Coding and Comprehension subtest intercepts varied slightly between groups. The hypothesized WISC-IV factor model described the data well. Factor patterns, first- and second-order factor loadings, intercepts, residual variances of measured subtests, and disturbances of first-order factors of the WISC-IV were generally invariant. Results suggested that WISC-IV index scores and subtests have the same meaning for children in both normative and clinical groups.     

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.     

Evaluating the invariance of the factor structure of the EPQ-R-N among adolescents

We examined the factor structure of the Neuroticism scale of the Eysenck Personality Questionnaire (EPQ-R-N; S. B. G. Eysenck, Eysenck & Barrett, 1985) and its factor invariance across sex and racial/ethnic groups in a sample of 1,979 adolescents. Using confirmatory factor analyses, we compared a hierarchical model to previous models of the EPQ-R-N and to single-factor and 3-factor structures. The hierarchical factor structure in which a general factor coexists with 3 group factors (depression, social concerns, and worry) was superior to alternative models. The general factor accounted for more than 60% of the variance in EPQ-R-N total scores and was invariant across sex and ethnicity. The 3 group factors varied across ethnicity and sex. We discuss the implications of these findings for conceptualization and assessment of neuroticism using the EPQ-R-N.     

What needs to be explained to account for age-related effects on multiple cognitive variables?

Structural equation methodology was used to investigate age-related influences across a number of cognitive variables in 204 adults ranging from 18 to 91 years of age with a hierarchical structure that contained 4 1st-order factors and 1 2nd-order common factor. Direct age relations were found to the common factor as well as to 1st-order speed and memory factors. Replicability of the findings was explored by investigating the same structure of age relations, using 2 different data sets, and a similar patten was found in each. These results suggest that at least 3 statistically distinct types of age-related influences are operating on a wide variety of cognitive variables and presumably require separate explanatory mechanisms.     

Evaluating the Invariance of the Factor Structure of the EPQ–R–N Among Adolescents

We examined the factor structure of the Neuroticism scale of the Eysenck Personality Questionnaire (EPQ–R–N; S. B. G. Eysenck, Eysenck & Barrett, 1985) and its factor invariance across sex and racial/ethnic groups in a sample of 1,979 adolescents. Using confirmatory factor analyses, we compared a hierarchical model to previous models of the EPQ–R–N and to single-factor and 3-factor structures. The hierarchical factor structure in which a general factor coexists with 3 group factors (depression, social concerns, and worry) was superior to alternative models. The general factor accounted for more than 60% of the variance in EPQ–R–N total scores and was invariant across sex and ethnicity. The 3 group factors varied across ethnicity and sex. We discuss the implications of these findings for conceptualization and assessment of neuroticism using the EPQ–R–N.     

Hierarchical structure of dysfunctional beliefs in obsessive-compulsive disorder

The Obsessive Beliefs Questionnaire was developed as a comprehensive measure of dysfunctional beliefs, which cognitive models consider to be etiologically related to obsessive-compulsive disorder. Obsessive Beliefs Questionnaire subscales tend to be highly correlated, which raises the question of whether obsessive-compulsive-related beliefs are hierarchically structured, consisting of lower-order factors loading on 1 or more higher-order factors. To investigate the nature and relative importance of these factors, a hierarchical factor analysis was conducted (n = 202 obsessive-compulsive disorder patients), using a Schmid-Leiman transformation. Results indicated a higher-order (general factor) and 3 lower-order factors: (i) responsibility and overestimation of threat, (ii) perfectionism and intolerance of uncertainty and (iii) importance and control of thoughts. The high-order factor accounted for more variance in Obsessive Beliefs Questionnaire scores (22%) than did the lower-order factors (6-7%), thereby underscoring the importance of the higher-order factor. Despite the importance of the higher-order factor, the lower-order factors significantly predicted unique variance in measures of obsessive-compulsive symptoms, including severity ratings of compulsions. These finding suggest that cognitive models of obsessive-compulsive disorder should take into consideration the hierarchic structure of obsessive-compulsive-related beliefs.     

Evidence for a general factor of behavioral activation system sensitivity

Individual differences in one’s propensity to engage the behavioral activation system (BAS) and behavioral inhibition system (BIS) have primarily been studied with Caver and White’s (1994) BIS/BAS scale. Whereas, Carver and White identified the BIS as a unidimensional scale, they identified three separable BAS group factors - drive, fun seeking, and reward responsiveness -which Carver urged against combining into a BAS total score. Despite this, a BAS total score has been used extensively although researchers have yet to test whether a BAS general factor exists and, if so, whether a BAS total score can be interpreted as primarily being a measure of the general factor. The current study observed that the best fitting BAS factor model of those we tested was a hierarchical model with three group facets and a general factor. This model was largely invariant across both sex and race/ethnicity. We show, for the first time, that a general factor accounts for the majority of the variance in BAS total scores. Due to the superior fit of the hierarchical model and variance accounted for by the general factor, we conclude that researchers are psychometrically justified in using a BAS total score.     

Indice d’aptitude général pour le WISC-IV : normes francophones

The Wechsler Children Intelligence Scale–Fourth Edition (WISC-IV, 2005) allows to calculate the FSIQ and four index scores: verbal comprehension, perceptual reasoning, working memory, and processing speed. In 1998, Prifitera and colleagues recommended to calculate the General Ability Index (GAI), as an alternative composite score. This score is based on Verbal Comprehension and Perceptual Reasoning only. The objective of the first study presented in this paper is to provide the GAI normative tables for the French WISC-IV; these tables were created using a statistical approximation procedure. The objective of the second study is to test the validity of these tables with data obtained from 60 children. Correlation between FSIQ and GAI is 0.91 and the relative mean difference is only 0.18 point. These tables, for the French version of the WISC-IV, allow using the GAI as an alternative measure of general ability.     

The Correlation of General Cognitive Ability and Psychomotor Tracking Tests

A study was conducted to investigate the nexus of cognitive and psychomotor tests as might be used for personnel selection and assessment. These two domains are frequently seen as independent. A multiple aptitude cognitive test battery and a psychomotor test battery were administered to 354 United States Air Force recruits. The average multiple correlation of the cognitive tests and each psychomotor score as a criterion was 0.34, corrected for range restriction. Confirmatory factor analyses disclosed general cognitive and general psychomotor factors, three lower-order psychomotor factors, and two lower-order cognitive factors. The general cognitive factor accounted for 39% of the variance and the general psychomotor factor accounted for 29% of the variance. Residualized, the lower-order factors accounted for between 10% and 3% of the variance. The average g saturations (loadings) of the cognitive and psychomotor tests were 0.82 and 0.34 respectively. An implication for personnel selection is that the incremental validity of psychomotor tracking tests beyond the validity of cognitive tests will be small due to the commonality of measurement. A further implication of findings is the need to study the validity of the general and specific psychomotor factors.     

Etiology of obsessions and compulsions: a behavioral-genetic analysis

It is unknown whether various types of obsessive-compulsive (OC) symptoms have a common genetic or environmental etiology. For example, it is unknown whether hoarding is etiologically associated with prototypic OC symptoms, such as washing, checking, and obsessing. Also unknown is whether particular OC-related symptoms are etiologically linked to the general tendency to experience emotional distress (negative emotionality). To investigate these and other issues, a community sample of 307 pairs of monozygotic and dizygotic adult twins provided scores on 6 OC-related symptoms (obsessing, neutralizing, checking, washing, ordering, and hoarding) and 2 markers of negative emotionality (trait anxiety and affective lability). Genetic factors accounted for 40%-56% of variance in the 8 phenotypic scores (M = 49% of variance for OC-related symptoms). Remaining variance was due to nonshared (person-specific) environment. More detailed analyses revealed a complex etiologic architecture, where OC-related symptoms arise from a mix of common and symptom-specific genetic and environmental factors. A general genetic factor was identified, which influenced all symptoms and negative emotionality. An environmental factor was identified that influenced all symptoms but did not influence negative emotionality. Each of the 6 types of symptoms was also shaped by its own set of symptom-specific genetic and environmental factors. The importance of genetic factors did not vary as a function of age or sex, and the architecture of general and specific etiologic factors was replicated for participants having relatively more severe OC symptoms. Gene-environment interactions were identified. Implications for an etiology-based classification system are discussed.     

Empirically derived groups in the assessment of recovery from aphasia.

This paper examines the pretreatment intercorrelation matrix of the subtests of the Porch Index of Communication Ability to derive factors reflecting components of language impairment. In addition to a general factor reflecting overall language dysfunction, five specific factors reflecting verbal competency (fluency), graphic-verbal expression, gestural-verbal expression, gestural-nonverbal comprehension, and graphic-geometric comprehension were found which accounted for 90.6% of the total variance. A cluster analysis of the five pretreatment factor scores yielded six groups which accounted for 79% of the variance for these factors. These groups were differentiated primarily in terms of impairment and showed a high rate of accuracy prediction for group membership (97.5%). These groups were extremely stable, as shown by the 75% accurate prediction rate derived from the post-treatment factor scores. The effectiveness of this model in generating homogeneous and highly discriminable groups based on objective measures of the patient's language functions indicates that classification of patients into empirical groups should be a major concern of any research design. Implications for assessing effectiveness of therapeutic intervention and the design of test battery were also discussed.     

Hierarchical Structure of Dysfunctional Beliefs in Obsessive‐Compulsive Disorder

The Obsessive Beliefs Questionnaire was developed as a comprehensive measure of dysfunctional beliefs, which cognitive models consider to be etiologically related to obsessive‐compulsive disorder. Obsessive Beliefs Questionnaire subscales tend to be highly correlated, which raises the question of whether obsessive‐compulsive‐related beliefs are hierarchically structured, consisting of lower‐order factors loading on 1 or more higher‐order factors. To investigate the nature and relative importance of these factors, a hierarchical factor analysis was conducted (n = 202 obsessive‐compulsive disorder patients), using a Schmid‐Leiman transformation. Results indicated a higher‐order (general factor) and 3 lower‐order factors: (i) responsibility and overestimation of threat, (ii) perfectionism and intolerance of uncertainty and (iii) importance and control of thoughts. The high‐order factor accounted for more variance in Obsessive Beliefs Questionnaire scores (22%) than did the lower‐order factors (6–7%), thereby underscoring the importance of the higher‐order factor. Despite the importance of the higher‐order factor, the lower‐order factors significantly predicted unique variance in measures of obsessive‐compulsive symptoms, including severity ratings of compulsions. These finding suggest that cognitive models of obsessive‐compulsive disorder should take into consideration the hierarchic structure of obsessive‐compulsive‐related beliefs.     

Factor structure of the Dysfunctional Attitude Scale (Form A) and the Automatic Thoughts Questionnaire: an exploratory study

The factor structure of the Norwegian version of the Dysfunctional Attitude Scale and the Automatic Thoughts Questionnaire was investigated with a sample of 344 male military recruits. Principal factor analyses with promax rotation indicated four factors for the former, labeled Performance Evaluation, Need for Approval, Autonomous Attitude, and Perfectionism which accounted for 15.5%, 3.6%, 2.6%, and 2.5% of the total variance, respectively. Two factors comprised the latter. Factor 1 was labeled Negative Self-concept and Personal Maladjustment and accounted for 40% of the total variance, and Factor 2 was labeled Desire for Change and Negative Expectations and accounted for 6.3% of the total variance. The findings may be useful in identifying the specific dysfunctional beliefs and negative automatic thoughts exhibited by military recruits. Such information can also contribute to the development of more effective treatment interventions.     

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.     

On the division of working memory and long-term memory and their relation to intelligence: A latent variable approach

The present study examined the extent to which working (WM) and long-term memory (LTM) reflect the same, related, or completely different constructs and how they relate to other cognitive ability constructs. Participants performed various WM, recall, recognition, general fluid (gF) and general crystallized intelligence (gC) measures. Confirmatory factor analyses suggested that the memory measures could be grouped into three separate yet correlated factors (WM, recall, and recognition) and that these factors were strongly related to gF, but were related less so with gC. Furthermore, it was found that the common variance from the three memory factors could be accounted for by a higher-order memory factor which was strongly related to gF, but less so with gC. Finally, structural equation modeling suggested that both the variance common to the WM tasks and the variance common to all the memory tasks accounted for a unique variance in gF. These results are interpreted within an embedded process model of memory and suggest that WM and LTM tasks measure both shared and unique processes, which are important for intelligence.     

Sex differences in general knowledge in German high school students

This study examines the hypotheses that (1) 17 domains of general knowledge can be identified; (2) these are positively intercorrelated and form a general factor of general knowledge; (3) there are sex differences in the different domains of general knowledge; and (4) males have more general knowledge in more of these domains than females and in the general factor. The study tests these hypotheses on a sample of 302 German high school students. All the hypotheses were confirmed. All the domains of general knowledge were positively intercorrelated. A general factor was found that explained 31.3% of the variance. Males achieved significantly and substantially higher scores than females in general knowledge of 0.60d. The only area in which females scored significantly higher than males was Nutrition for which there was a medium size effect size (d=0.50). The results are highly similar to those among university students in Northern Ireland reported by Lynn, Irwing, and Cammock (2002).