This study tests the potentials of a novel momentary assessment method, called the Electronically Activated Recorder (EAR), for studying real-world communication processes in couples coping with breast cancer. The EAR is an unobtrusive observation sampling method that operates by periodically recording snippets of ambient sounds from participants'immediate environments. In proposing a naturalistic observation approach to studying real-world coping, the application responds to concerns in the field that too much of what is known about coping is derived from questionnaires. In implementing this approach within a couple-centered, dyadic research paradigm, it builds on recent theoretical and methodological advances in the field of relationship- focused coping. Forty breast cancer patients and their partners will wear the EAR over one weekend during active treatment. The patients'and the partners'psychological adjustment will be assessed during the initial study session and at a two-month follow-up. Within Aim 1 we will map the topography of the couples'daily interactions through examining with whom and about what breast cancer patients and their partners talk in their natural daily social encounters. For this, the recorded EAR sound bites will be coded for with whom participants talked (i.e. their partner vs. a friend or family member) and content analyzed for the topics of their interactions (broad coding of 'about cancer'versus 'about other topic'plus inductive computerized content analysis of specific conversational themes). The findings will inform current social network models of coping with cancer. Aim 2 extends Aim 1 and examines how individual differences in the types and content of breast cancer patients'and their partners'interactions are related to their adjustment to the situation. Based on predictions from disclosure theory and relationship maintenance theory we predict that both aspects of cancer- related and non-cancer related conversations will predict couples'psychological adjustment. We further argue that the importance of routine relationship-maintenance interactions (relative to direct, illness-focused interactions) has been underestimated in prior coping research. Together, this study seeks to enhance mental health researchers'and practitioners'understanding of the role that couple's real-world communications play in the context of coping with cancer. Its findings will provide important input for the development of effective couple-focused, coping and communication-enhancing cancer support interventions. PUBLIC HEALTH RELEVANCE: Being diagnosed with cancer is a highly stressful life event that often has critical mental health consequences for the patient as well as for the partner who is living with the patient. This research uses a novel naturalistic observation method, a digital voice recorder that periodically samples snippets of ambient sounds, to examine to whom and about what couples coping with breast cancer talk in their real-world conversations during the time of adjuvant treatment. It further examines how differences in what patients and partners talk about are related to their psychological adjustment to the disease. Knowing with whom and about what couples naturally talk in their daily interactions and how patients and partners use their daily conversations for coping with the cancer experience is crucial for developing effective coping and communication-enhancing psychosocial cancer support interventions and for identifying couples who experience the greatest need for such interventions.