Interpersonal processes in daily life: Within-person dynamics of experiential avoidance, responsiveness, vulnerability, and momentary loneliness

Introduction: Loneliness is increasingly recognized as a critical public health concern, yet its moment-to-moment determinants remain poorly understood. From a contextual behavioral perspective, loneliness may emerge as a downstream consequence of patterns of interpersonal behavior shaped by experiential avoidance and disrupted intimacy processes. Methods: The present study examined a contextual behavioral science-based model of loneliness grounded in the Interpersonal Process Model of Intimacy using ecological momentary assessment. Participants (N = 31) completed surveys (N = 1201) three times daily for up to 14 days assessing experiential avoidance, interpersonal processes (vulnerability and responsiveness), perceived connection, loneliness, and mental health. Results: Results indicated that both the quantity and quality of social interactions were associated with momentary loneliness, with perceived connection demonstrating a stronger association than interaction frequency. Momentary feelings of connection were predicted best by provided and experienced responsiveness rather than expressed or received vulnerability. Efforts to control emotions, conceptualized as experiential avoidance, were not associated with the number of social interactions but was indirectly associated with connection through increased vulnerability, suggesting its role in shaping the quality rather than quantity of interpersonal engagement. Although strong concurrent associations were observed across variables, lagged effects were largely nonsignificant, indicating that these processes may operate primarily at a momentary level. In contrast, mental health predicted subsequent loneliness, whereas loneliness did not predict later mental health. Discussion: Results highlight the importance of targeting interpersonal processes and psychological flexibility to reduce loneliness and suggest that loneliness may be best understood as a dynamic, context-dependent process unfolding in daily life.