Abstract
Extradyadic sexual involvement (ESI) is associated with negative consequences for individuals and threatens couple stability. Research on ESI in unmarried samples has been marked by methodological limitations, such as examining only mean levels of sexual satisfaction or frequency to predict later ESI as opposed to changes in various aspects of the sexual relationship over time. The current study compared linear trajectories of four aspects of the sexual relationship-sexual satisfaction, frequency of sex, comfort communicating about sex, and sexual closeness-between individuals in opposite-sex, unmarried relationships who subsequently engaged in ESI (ESI group; n = 183) compared to individuals who did not engage in ESI (non-ESI group; n = 603). Trajectories of relationship adjustment were also evaluated leading up to ESI as well as controlled for in models evaluating the sexual relationship. Results indicated that relationship adjustment declined for individuals preceding ESI, but did not change for the non-ESI group. When controlling for relationship adjustment, comfort communicating about sex decreased for ESI women but increased for ESI men. Some results became nonsignificant after controlling for relationship adjustment, including that sexual satisfaction declined more steeply in the ESI group compared to the non-ESI group, and ESI women significantly decreased in sexual closeness while ESI men demonstrated no significant change. Some mean level differences were also discovered directly before ESI. Conclusions include that changes in a couple's sexual relationship and relationship adjustment are associated with ESI behaviors, providing novel information regarding normative and risk trajectories.