Shared knowledge is an important factor for the introduction and implementation of strategies in teams. It is also used to explain performance differences between teams. Team performance is considered critical for success for companies. Therefore, it is important to know which aspects of shared knowledge influence team performance. To determine this, it is necessary to discuss appropriate methods which are applicable to the object of research. The objects of research in this thesis are highly idiosyncratic mental models. They form the framework in which decisions take place, according to the perception of the individuals. Highly idiosyncratic mental models include domain knowledge, and the structure of the domain.This thesis addresses the question of comparing different idiosyncratic mental models with regard to their similarities and differences. Such a comparative approach was developed and validated in five empirical studies. Its result is the "Meaning Relations Tool", a rule system to assess the similarities and differences of concepts of different idiosyncratic mental models. It is based on repeating measurements as a combination of holistic and collective elicitation surveys. The assessment of similarity is performed by the participants themselves. For this reason, conclusions can be drawn about the individual and team performance.