An identification method is described which allows the approximation of experimental observations by means of a phenomenalistic model. The method is theoretically based on system theory and is adapted to the needs of behavioural science. Special emphasis will be laid on a system representation, which is transferable to a large group of dynamic systems as well as on an exact formulation of the assumptions connected with the proposed method. A short summary of results determined by a behaviour analysis in the field of social psychology will give a practical view of the possibilities and limits of the described identification method.