Abstract
Infidelity is defined as unapproved romantic or sexual behaviors outside of one’s relationship. Previous literature has identified characteristics of the partner involved in infidelity; this study investigates the Big Five personality traits (openness, conscientiousness, extraversion, agreeableness, and neuroticism) of uninvolved partners. Relationship quality and physical intimacy are also examined within a married subsample. Data was drawn from the second wave of the National Survey of Midlife Development in the United States (MIDUS), collected through telephone interviews and self‐administered questionnaires between 2004 and 2006. Results for the overall sample (N = 1,577) indicate that conscientiousness is negatively associated with lifetime partner infidelity. Within the married subsample (n = 898), conscientiousness is negatively associated with spousal infidelity, and agreeableness is positively associated with spousal infidelity.