Actor-Partner Interdependence Model

The Actor-Partner Interdependence Model (APIM), formalized by Kenny, Kashy, and Cook, is the standard framework for analyzing dyadic data in which two people's outcomes depend on both their own and their partner's characteristics. For each member of a dyad, the model estimates an actor effect -- the influence of a person's own predictor on their own outcome -- and a partner effect -- the influence of the partner's predictor on the person's outcome -- while explicitly modeling the statistical non-independence of the two members' scores. For example, a person's relationship satisfaction may depend on their own attachment anxiety (actor effect) and on their partner's attachment anxiety (partner effect). By simultaneously estimating these effects and accounting for the correlation between partners, the APIM avoids the bias of treating dyad members as independent and reveals how individuals in relationships shape each other, making it indispensable for research on couples, families, and other interacting pairs.