Graphic methods for interpreting longitudinal dyadic patterns from repeated-measures actor–partner interdependence models

Researchers commonly use repeated-measures Actor-Partner Interdependence models (RM-APIM) to understand how romantic partners change in relation to one another over time. However, traditional  interpretations of the results of these models do not fully or correctly capture the dyadic temporal patterns estimated in RM-APIM. Interpretation of results from these models largely focuses on the meaning of single parameter estimates in isolation from all the others. However, considering individual coefficients separately impedes the understanding of how these associations combine to produce an interdependent pattern that emerges over time. Additionally, positive within-person, or actor, effects are commonly misinterpreted as indicating growth from one time point to the next when they actually represent decline. We suggest that change-as-outcome RMAPIMs and vector field diagrams (VFDs) can be used to improve the understanding and presentation of dyadic patterns of association described by standard RM-APIMs. The current paper briefly reviews the conceptual foundations of RM-APIMs, demonstrates how change-as-outcome RM-APIMs and VFDs can aid interpretation of standard RMAPIMs, and provides a tutorial in making VFDs using multilevel modeling.