Infidelity can have harmful consequences for all those involved. Although prior research has demonstrated some reliable associations between certain personality traits and infidelity, the associations between other personality traits and infidelity are less clear. Moreover, prior research has been limited in addressing the role of partner personality and whether any effects are independent of relationship satisfaction. Thus, we pooled data from two 3-year longitudinal studies of newlywed couples to examine the associations between both couple members’ personality (Big Five and narcissism) and infidelity, controlling and not controlling for marital satisfaction. Wives high (versus low) in extraversion and husbands and wives with partners high (versus low) in neuroticism or extraversion were more likely to engage in infidelity regardless of whether we controlled for satisfaction. Husbands with partners high (versus low) in narcissism were more likely to engage in infidelity, though this effect was no longer significant when controlling for satisfaction. These findings demonstrate that even predicting a behavior as self-oriented as infidelity requires considering the qualities of both couple members, highlighting the importance of adopting a dyadic approach to relationships.

Since Spring 2021, I have been on the Editorial Board for Personal Relationships as an International Section Peer Mentor. In the International Section, I work to diversify relationship science with a team of relationship scientists. In this role, I have learned more about diversity, and in turn, I have become inspired to reflect on other strategies I could partake in to assist in further diversifying relationship science. I aim to share those insights in this commentary through recommendations for relationship scientists. In addition to sharing these recommendations, I describe my positionality in a positionality statement, and I provide background on what diversity means to me and my current expertise in the subject matter. There are several recommendations in this commentary, and they involve all steps of the research process. I encourage relationship scientists to educate themselves, to consider the various diversities when developing their research questions, to initiate collaborations with and learn from other research teams whenever possible, to ensure that they are not unintentionally excluding underrepresented groups, to reflect on how they report participant demographic data, and to consider drafting their own positionality statements.