Relationship quality is influenced by actor and partner effects but not by similarity and discrepancy effects: A study of Brazilian and Czech populations

Evidence suggests that personality may influence romantic relationship quality in several ways. Quality of relationship can be affected by an individual's personality (actor effect), partner's personality (partner effect), by discrepancy between ideal and actual partners' personalities (discrepancy effect), or by similarity between partners' personalities (similarity effect). Most studies, however, focus on just one of these effects, their results are often ambiguous, and based on western populations. We tested all these effects at once in individuals from two distinct populations: Brazil and the Czech Republic. In total, 626 individuals in a long-term committed relationship completed the Ten-Item Personality Inventory for their own, actual, and ideal partner, and the Revised Dyadic Adjustment Scale. Hierarchical categorical regression analyses showed that the actor and partner effect contributed significantly, although weakly, to dyadic adjustment, while the impact of discrepancy and similarity was negligible. Explained variance was around 10% for the actor effect, around 30% jointly for actor and partner effects, and around 40% jointly for actor, partner, discrepancy, and similarity effects. The overall results were similar for both studied populations. Importantly, all reported effect sizes are small, which suggests that other factors contribute to dyadic adjustment more substantially.