Response to Mathias and Nettelbeck on the structure of competence: need for theory-based methods to test theory-based questions.

In this paper, we respond to a 1992 study by Mathias and Nettelbeck in which, using exploratory factor analysis, they argued that the structure of intelligence in persons with mental retardation deviates from the model previously proposed by Greenspan. Applying the LISREL method of confirmatory factor analysis to Mathias and Nettelbeck's original correlation matrix, we found the Greenspan model (in which social and practical intelligence form separate factors) to be an equally plausible interpretation of their data as the single (Interpersonal Competence) factor found by Mathias and Nettelbeck. The fundings are discussed with respect to (a) the importance of using theory-based methods when addressing theory-based questions and (b) the role of social intelligence in the ongoing controversy over the meaning of mental retardation.