We develop and evaluate psychological tests and questionnaires on the basis of classical test theory and probabilistic test theory. The instruments include knowledge tests for specific domains, computer-based tests of cognitive performance, and questionnaires assessing relevant constructs of social perception. In addition, we use advanced models of item response theory to analyze response tendencies and to test assumptions on the interpretation of different response formats. Another focus of research aims at probabilistic test models for the analysis of change over time and for the evaluation of intervention effects.