Tuesday, November 24, 2009

Dissertation dish: New insights on the subdomains of Gs (processing speed)

Exploring the relationships among various measures of processing speed in a sample of children referred for psychological assessments by Nelson, Megan A., Ph.D., University of Virginia, 2009 , 102 pages; AAT 3348732


Processing speed is a robust psychometric factor in modern tests of cognitive ability (Carroll, 1993), but the common factors underlying mental speed and its contributions to individual differences in functioning are not well understood. The goal of the current study was to further explore mental speed by conducting a confirmatory factor analysis (CFA) on 11 speeded subtest scores. It was hypothesized that the 11 subtests would be best represented by a four-factor model. These four factors were then submitted to a cluster analysis to identify whether certain patterns of factor scores were related to different demographic characteristics, diagnoses, or referral questions. It was hypothesized that Learning Disorder, Attention-Deficit/Hyperactive Disorder, and comorbid LD/ADHD diagnoses would be most likely to have unique processing speed factor patterns.

Participants were 186 children (ages 6 - 18 years old) referred to a university-based clinic for a comprehensive psychological evaluation. The CFA indicated that although the 11 measures are all speeded, they are best represented as four distinct constructs, labeled perceptual speed, naming facility, academic facility, and reaction time in this study. The clusters produced in this study appeared to be most highly differentiated by level (likely influenced by intelligence level) and by pattern only in respect to reaction time factor scores. Therefore, both the CFA and cluster analyses lend support to Cattell-Horn-Carroll cognitive theory's distinction between cognitive processing speed (Gs) and decision/reaction time (Gt). Additionally, the CFA results suggest that Gs may be multifaceted, but the cluster analysis did not differentiate clusters based on the processing speed factors. Although the results of this study have important implications for both assessment clinicians and cognitive theory, further research is needed to clarify the constructs of processing speed and reaction time as well as to identify the clinical implications of different processing speed pattern

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