Masumi Iida’s research interests span several domains of social, health, and quantitative psychology. Her primary substantive interest lies in understanding stress, coping, and well-being, with emphases on dynamic processes and close relationships. Most of her research has concentrated on understanding the determinants and consequences of social support using a daily diary method. Her work on social support seeks 1) to examine the situational determinants of support provision and 2) to investigate the context and situations in which receiving support has positive outcomes. Her research also focuses on individuals’ responses to challenging situations by examining daily coping mechanisms. Research in this area poses multiple data-analytic challenges. The complexities associated with longitudinal and dyadic data require a deep understanding of quantitative methods designed to model statistical dependency. She has developed skills in the use of multilevel statistical methods that enable researchers to simultaneously model within- and between-unit effects allowing for the study of dynamic (longitudinal) and dyadic data.