The proposed research examines the motivational and cognitive mechanisms underlying excitement and boredom in long-term relationships, focusing specifically on the apparent beneficial effect of joint participation in `exciting` activities. Although several processes are probably involved (misattribution of arousal, positive affect from success, conformance with romantic ideals, cooperation, etc.), the proposed research focuses on motivational processes associated with novelty, efficacy, exploration, curiosity, and optimal level of arousal, as integrated and extended to relationship issues by a relatively new theoretical approach, the self-expansion model. Hypotheses include the prediction that participating together in novel, arousing activities increases relationship satisfaction, and that this effect is moderated by length of relationship, individual differences, and saliency of the partner at the time of the activities and is mediated by increased perceived self-efficacy; that there is a positive effect of participants' believing that such activities enhance competence; that there is an influence of self-expansion processes over and above various other potential mechanisms; and that some of these other potential mechanisms also have an effect, over and above self-expansion processes. Six laboratory experiments test these hypotheses by randomly assigning volunteer couples to participate in activities structured by the researchers and assessing change in relationship satisfaction using self-report, systematic observation, and other measurement procedures. %%% Marital satisfaction impacts all areas of life--overall life satisfaction, mental health, physical health, and job performance--as well as the stability of families and the attendant effects on children. Unfortunately, there is a well-documented decline in satisfaction after the early relationship years, but scientific research on marriage provides little precise understanding of that decline, or of the general role of boredom in day-to-day relationship life. One way of understanding relationships proposes that the high satisfaction in early years is due to each member of a relationship feeling expanded and enhanced by the other, and holds that these feelings fade because partners get used to each other. But if the couple at this point can engage, together, in activities that are enhancing to both, the satisfaction from such activities will be linked with the relationship--and preliminary studies support this prediction. The proposed experiments study these ideas while carefully sorting out the other ways of understanding boredom in relationships and the effect on it of participating together in various kinds of activities. These experiments will first assess relationship satisfaction of volunteer married couples using established measures. Couples will then participate together in an activity and have their satisfaction assessed again. The activity will differ, varying in ways that real-life activities might, such as the activity being very novel versus commonplace or involving a lot or a little cooperation. Predictions are tested by comparing change in couples' marital satisfaction from before to after the different activities. This research is designed to lead to direct practical applications in marital counseling and family education.