Intelligence and its assessment across the life span : analyzing construct and criterion validity

Intelligence is the strongest predictor of a diverse range of positive outcomes in life, such as scholastic achievement, career success, health, and longevity. Hence, many conclusions are drawn from intelligence test results and these can have an impact on high-stakes decisions regarding, for example, a child’s school career or an adult’s employment. To accurately interpret the results of an intelligence test, its validity has to be ensured. This cumulative dissertation includes four studies that extend current knowledge on the construct and criterion validity of currently used intelligence tests: The factor structure of the Reynolds Intellectual Assessment Scales (RIAS) and its measurement invariance were evaluated across its four language versions (Danish, English, German, and Spanish) and across individuals with and without a migration background in the German RIAS version. Further, the predictive power of four intelligence tests currently used in German-speaking countries was analyzed for longitudinal scholastic achievement (i.e., school grades), as well as the predictive power of the RIAS and the incremental validity of conscientiousness for career success (i.e., occupational status, income, job satisfaction) in adults. Regarding construct validity, findings support the RIAS factor structure as well as measurement invariance across its four language versions and across German-speaking individuals with and without a migration background. Further, individuals with a migration background showed lower verbal and nonverbal intelligence. Regarding criterion validity, currently used intelligence tests were a predictor for longitudinal school grades. Furthermore, the RIAS showed positive associations with concurrent occupational status, while conscientiousness could explain variance in income and job satisfaction. This points to further factors that might be relevant for psychological assessment beyond intelligence. In conclusion, the present dissertation provides evidence for construct and criterion validity of currently used intelligence tests in German-speaking countries, indicating a valid intelligence assessment across the life span.