Measurement precision and test score interpretation of intelligence tests in Germany: Assessing the evidence for ability differentiation, age differentiation, and their interaction.

• Applicant: Dr. Moritz Lion Breit
• Subject Area: Personality Psychology, Clinical and Medical Psychology, Methodology ; Developmental and Educational Psychology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 499340216

Intelligence tests are among the most important and widely used psychometric test procedures. For over 100 years, new tests have been continuously developed and existing ones revised. Many of the tests provide a general intelligence score as well as scores for more specific cognitive abilities, which can be used to create ability profiles. In the evaluation and interpretation of the tests, it is usually assumed that both the measurement accuracy and the validity of the ability profiles are given across the entire spectrum of intelligence - independent of the characteristics of the tested person. However, this assumption can be questioned from a theoretical perspective. According to differentiation hypotheses of intelligence, age and ability of a test person systematically influence the relationship between different test scales and their measurement accuracy. The ability differentiation hypothesis posits that the importance of general intelligence for specific cognitive performances decreases as the subject's ability increases. According to the age differentiation hypothesis, the importance of general intelligence decreases with increasing age. According to the age dedifferentiation hypothesis, there is an exactly opposite trend at very high ages. In addition, interactions between ability differentiation and age differentiation have been postulated. The empirical basis for these hypotheses is weak due to a small number of methodologically adequate studies. Thus, it is still largely unclear which differentiation effects actually exist and to what extent they can be generalized across different age ranges and test content. We therefore aim to generate comprehensive empirical evidence with two large-scale studies. We focus on German-language structure of intelligence tests. In the first study, we investigate ability and age differentiation and their interaction in the standardization data of the Wechsler tests across the lifespan. The norm data of the different test versions will be statistically linked which allows for an investigation from preschool age to late adulthood. The results will show at which age which differentiation effects are observable. In the second study, the standardization samples of 16 intelligence tests for children and adolescents will be analyzed for differentiation effects with uniform statistical methodology and the results will subsequently be meta-analytically integrated. Intelligence tests are used in childhood and adolescence in particular for momentous diagnostic decisions. Therefore, robust evidence on differentiation hypotheses is especially relevant for these age groups. The results of this project thus contribute significantly to differentiated, evidence-based recommendations for the construction, revision, and use of intelligence tests.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Martin Brunner; Professorin Dr. Franzis Preckel