My primary goal is to develop psychological theories, and to solve substantial psychological problems, both in basic research as well as in practical applications (e.g. technology-enhanced learning). In many cases meeting this objective cannot be achieved by simply employing well-known methods of psychological research, but requires to develop new approaches.  

As my research interests are spread across a spectrum of quite different psychological areas I am using and developing a whole variety of methods: Principles of representational measurement theory are applied to a formal treatment of binocular distance perception. Classical and modern methods of psychophysics, including functional equations techniques, are used to characterize invariants in lightness and brightness perception, and to determine their impact on the form of the psychophysical function. A new experimental method for a psychological investigation of individual verbal concepts was developed within a set-theoretic framework. Sophisticated methods for parameter estimation, model testing, and identifiability checks are developed for probabilistic knowledge structures. These models provide the theoretical basis for various applications, like assessing competencies in quite diverse areas (such as arithmetic, or orthography), or developing innovative approaches to personality diagnostics.