Differentiation of cognitive abilities in the WAIS-IV at the item level

• Published in: Intelligence (Norwood) Vol. 65; pp. 48 - 59
• Main Authors: Molenaar, Dylan, Kő, Natasa, Rózsa, Sandor, Mészáros, Andrea
• Format: Journal Article
• Language: English
• Published: New York Elsevier Inc 01.11.2017; Elsevier Science Ltd
• Subjects: Ability differentiation; Age; Age differences; Age differentiation; Cognitive ability; Differentiation; Discriminant analysis; Intelligence; Non-linear factor analysis; Nonlinear equations; Power; Simulation; Spearman's law of diminishing returns; Standardization; Spearman's law of diminishing returns; Ability differentiation; Non-linear factor analysis; Age differentiation
• ISSN: 0160-2896; 1873-7935
• DOI: 10.1016/j.intell.2017.10.004

It is known that studying the differentiation of cognitive abilities is associated with many methodological challenges. In the recent years, methods have been developed to address these challenges. However, these methods require that the item scores of an intelligence test are combined into a composite score which may affect the power to detect the differentiation effect or even produce spurious results. Therefore, in this study, an item level approach is presented that can be used to simultaneously test for ability differentiation, age differentiation, and age differentiation-dedifferentiation. The new method is investigated in two small simulation studies, and applied to the standardization data of the Hungarian WAIS-IV. Results indicate that the ability differentiation effect is consistently present in the items of the WAIS-IV while there is no consistent age differentiation and/or age differentiation-dedifferentiation effect. •Testing the differentiation of cognitive abilities using (age standardized) composite scores may produce spurious results.•We present an item level approach to simultaneously test for ability differentiation and age (de)differentiation.•Application indicates that the ability differentiation effect is consistently present in the items of the Hungarian WAIS-IV•We found no consistent age differentiation and/or age differentiation–dedifferentiation effects.