Higher-order factor structures for the WISC-IV: implications for neuropsychological test interpretation.

Factor-analytic studies support a hierarchical four-factor model for the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) with a prominent general, third-order factor. However, there is substantial disagreement on which type of higher-order model best fits the data and how different models should guide test interpretation in clinical practice, with many studies concluding interpretation should primarily be focused on general indicators of intelligence. We performed a series of confirmatory factor analyses with the WISC-IV standardization sample (N = 2,200, ages 6-16 years) to examine model fit and reexamined models used to support test interpretation at the general level. Consistent with previous research, bifactor models were difficult to identify; however, compared with bifactor and hierarchical models, the correlated factors model with no general higher-order factor provided the best fit to the data. Results from this study support the basic four-factor model specified in the WISC-IV technical manual, with test interpretation primarily focused at the factor level, rather than the general level suggested in previous studies.

Development and evaluation of an online, multicomponent working memory battery.

Research has demonstrated strong connections among working memory (WM), higher-level cognition, and academic achievement. Despite the importance of WM, currently available WM tests have practical limitations and lack comprehensive coverage of multiple WM components. The Working Memory Battery (WOMBAT) includes nine subtests measuring multiple content domains and processing demands, in accordance with contemporary WM theoretical frameworks. The current study evaluated the WOMBAT factor structure and identified misfitting items using confirmatory factor analysis and Rasch modeling with scores from 125 adolescents and 177 adults (N = 302). Overall, results indicated the WOMBAT measures separate Verbal, Static Visual-Spatial, and Dynamic Visual-Spatial dimensions, and that more than 98% of items contribute to measurement of those dimensions. This provides support for the theoretical organization of WM into three distinct content domains in the WOMBAT. Misfitting items were identified using infit and outfit indices for further review to improve reliability and stability. Results also demonstrated adequate person separation and Rasch person reliability and item reliability. Test-retest reliability and internal consistency coefficients suggest adequate reliability for early-stage research, but further refinement is needed before the WOMBAT can be used for individual decision making. Implications for future test development and research on the WM construct are provided.

The relationship of global form and motion detection to reading fluency.

Visual motion processing in typical and atypical readers has suggested aspects of reading and motion processing share a common cortical network rooted in dorsal visual areas. Few studies have examined the relationship between reading performance and visual form processing, which is mediated by ventral cortical areas. We investigated whether reading fluency correlates with coherent motion detection thresholds in typically developing children using random dot kinematograms. As a comparison, we also evaluated the correlation between reading fluency and static form detection thresholds. Results show that both dorsal and ventral visual functions correlated with components of reading fluency, but that they have different developmental characteristics. Motion coherence thresholds correlated with reading rate and accuracy, which both improved with chronological age. Interestingly, when controlling for non-verbal abilities and age, reading accuracy significantly correlated with thresholds for coherent form detection but not coherent motion detection in typically developing children. Dorsal visual functions that mediate motion coherence seem to be related maturation of broad cognitive functions including non-verbal abilities and reading fluency. However, ventral visual functions that mediate form coherence seem to be specifically related to accurate reading in typically developing children.

Cognitive and developmental influences in visual-motor integration skills in young children.

Measures of visual-motor integration skills continue to be widely used in psychological assessments with children. However, the construct validity of many visual-motor integration measures remains unclear. In this study, we investigated the relative contributions of maturation and cognitive skills to the development of visual-motor integration skills in young children (N = 856). We used a block regression analysis to determine the contribution of maturation, as indicated by age, followed by broad cognitive factors (Study 1) and subsequently by individual subtests in verbal and nonverbal domains subsumed under each factor (Study 2) in explaining score variance of the Bender Visual-Motor Gestalt Test (2nd ed.; BG-II; Brannigan & Decker, 2003) Copy and Recall scores in children between the ages of 4 and 7 years. Results confirm that maturation accounted for a large proportion of variance in both BG-II Copy and Recall performance, above which Stanford-Binet Intelligence Scale (5th ed.; SB-5; Roid, 2003) Quantitative Reasoning and Fluid Reasoning factors significantly contributed to visual-motor integration performance for the Copy phase, and SB-5 Quantitative Reasoning and Visual-Spatial factors accounted for a significant amount of variance for the Recall phase. Additionally, nonverbal domains were more related to visual-motor performance than verbal domains. Results from this study are interpreted to suggest nonverbal reasoning and visual-spatial attention are important contributing factors to visual-motor integration, as measured by the BG-II. Developmental implications of visual-motor integration skills, nonverbal problem solving, and mathematical competence are discussed.

Patterns and trajectories in Williams Syndrome: the case of visual orientation discrimination.

Williams Syndrome (WS) is a developmental disorder typified by deficits in visuospatial cognition. To understand the nature of this deficit, we characterized how people with WS perceive visual orientation, a fundamental ability related to object identification. We compared WS participants to typically developing children (3-6 years of age) and typical adults in an orientation discrimination task with four stimulus types (small circular, large circular, collinear elongated and parallel elongated gratings). We measured orientation discrimination thresholds and the proportion of orthogonal errors (i.e., mirror-image reversal errors). We evaluated how these metrics (1) are modulated by stimulus condition, and (2) vary with chronological or mental age. We found that orientation perception in WS is comparable to that of typically developing children. Orientation discrimination thresholds were better for elongated gratings than circular gratings across all participant groups. For large circular gratings, the proportion of orthogonal errors was disproportionately greater in WS participants and typically developing 3-6 year old children than in typical adults. Moreover, we found that the ability to judge orientation in WS improves with increasing mental age, but not chronological age. These results suggest that orientation discrimination in WS is developmentally arrested, as opposed to abnormal or delayed.