Person and situation effects should be measured in the same terms. A comment on Funder (2006)

In a recent paper in this journal, Funder Funder, D. C. (2006). Towards a resolution of the personality triad: persons, situations and behaviors. Journal of Research in Personality, 40, 21–34] stated that the effects of person and situation on behavior were independent in principle. In this comment, we argue that Funder’s claim is not a basic law of psychology, but a product of the common statistical approach to define person effects by Pearson correlations and situation effects by differences in group means. As an alternative, we suggest using Intraclass correlations (ICC) with an absolute agreement definition as indicators of intraindividual stability. This approach enables us to directly determine, how much people’s behavior varies or remains the same across situations. We demonstrate the usefulness of the ICC approach, by applying it to both hypothetical and empirical data. However, the question which model is more appropriate is a conceptual one and cannot be answered empirically.