The interpersonal functioning of couples in committed relationships has predominantly been examined using a medical model perspective of identifying and ameliorating problems in distressed couples, and doing so in an individualistic manner without considering their socio-cultural contexts. Researchers advocating multicultural approaches in the field of positive psychology promote the development of strength-based interventions with non-distressed couples that attend to collectivistic aspects of relationship functioning (Hawkins, Fowers, Carroll, & Yang, 2007).

Engagement in value-driven, prosocial behavior has been found to increase one's sense of purpose and mental health functioning, though it is unclear how it influences relationship functioning in couples who volunteer together, an example of such behavior. Joint engagement in play activities has also been found to enhance relationship quality. Research comparing these paths for individuals has consistently demonstrated that the former is a more robust predictor of positive psychosocial outcomes than the latter.

The present study prospectively compared the effects of joint volunteering for community service and joint play on the perceived relationship quality of a community sample of non-distressed couples. Drawing upon Behavioral Self-Regulation theory, the Thriving with Social Purpose framework and Marital Systems theory, a measure was created to assess whether couples' enhanced shared social purpose meditated the proposed association between joint volunteering and perceived relationship quality.

Couples' Relationship Quality was significantly enhanced by engaging in joint community service and play activities even after accounting for the significant effects of behavioral and socio-demographic characteristics. Differences were not found between these two conditions in the effects on relationship quality. Couples' Shared Social Purpose was significantly positively correlated with perceived relationship quality at pretest. Fifty-one couples were randomly assigned to each condition. Significant changes in Shared Social Purpose within and between conditions were not observed, though participants reported a significant increase in their shared vision for their relationship. Also, participants' perceived adequacy of social support from partners was not associated with outcomes.

This study advances the research comparing eudemonic and hedonic paths to well-being to the realm of interpersonal functioning and does so in a culturally thoughtful and strength-based manner. Theoretical implications, study limitations, and future directions are discussed.