According to this theory, characteristics of people influence the interactions between an individual and the context within which he or she operates, so that what a person brings into the context becomes part of the ‘person by context’ interaction. Contexts, in turn, are defined at several levels of analyses, and the various contexts within which one operates have reciprocal influences on each other. Finally, these interactions occur over time, changing both the person and the context(s) The key insight of this model is that individuals both act in contexts and act upon the context, and that the constant process of person–context interaction means that both persons and contexts need to be thought of in dynamic rather than static terms.