An investment model prediction of dating infidelity.

Many researchers have examined the justifications individuals give after being unfaithful to their romantic partners. However, very little research has been done to determine factors that actually predict infidelity. Two studies were conducted using the investment model (C. E. Rusbult, 1980,1983) to predict instances of physical and emotional infidelity in dating relationships. The 1st study found that commitment level at the beginning of the semester successfully predicted later emotional and physical infidelity. The 2nd study used an interaction diary method to predict the physical and emotional intimacy of nonpartner opposite-sex interactions over the course of the week-long university holiday known as spring break. Once again, commitment level before spring break successfully predicted the emotional and physical intimacy of such interactions. Given the high percentage of individuals in married relationships who engage in some form of extradyadic sexual involvement at some point in their marriage (roughly 50% in the United States; Kinsey, Pomeroy, & Martin, 1948; Tavris & Sadd, 1975), it is not surprising that researchers have sought to discover why. A substantial amount of research has delineated the categories of explanations that individuals give when asked for the reasons they have been unfaithful to their romantic partners. The explanations are diverse and cover a great deal of interpersonal territory. However, the territory often falls within the realm of post hoc explanation, the nature of which could well be tainted by motivated bias and inaccuracy. Very little research has been done to determine factors that actually predict infidelity from variables measured before the behavior occurred. The present research represents an attempt to predict dating infidelity using a model that has successfully predicted a variety of other important relationship behaviors: the investment model (Rusbult, 1980, 1983). Before launching into a discussion of the reasons for infidelity, it is important that we specifically explain our working definition of the concept. We maintain that infidelity is represented by the combination of (a) the feeling that one's partner has violated a relationship norm regarding the nature of the partner's interactions with someone else and (b) the fact that violation of this relationship norm typically elicits sexual jealousy and rivalry. Infidelity, thus, can be differentiated from behavior that is merely extradyadic but does not represent a violation of relationship norms regarding exclusivity. It is also important to note that such sexual jealousy appears to be culturally universal (e.g., Buss, 1994) and therefore may have some impact over and above specific cultural or relationship norms. Although the present research uses a North American sample of college dating relationships, we believe that the research reflects basic, universal processes that would most likely