My research focuses on understanding the formation, maintenance, and functions of personal relationships during adulthood. My work in recent years has been influenced by attachment theory and recent conceptualizations of responsiveness in relationships. Specifically, I have been investigating the mechanisms by which close relationships influence relational and psychological well-being as well as physical health over time (e.g., Ong, Gardner, Urganci, Gunaydin, & Selcuk, 2020; Selcuk, Gunaydin, Ong, & Almeida, 2016; Selcuk & Ong, 2013; Selcuk, Stanton, Slatcher, & Ong, 2017; Selcuk, Zayas, Gunaydin, & Hazan, 2012; Slatcher & Selcuk, 2017; Slatcher, Selcuk, & Ong, 2015; Stanton, Selcuk, Farrell, Slatcher, & Ong, 2019; Tasfiliz, Selcuk, Gunaydin, Slatcher, Corriero, & Ong, 2018). In a second and related line of work, I am interested in understanding how marital processes influence parenting (Kocak Mouratidis, Ucanok, Selcuk, & Davies, 2020; Selcuk et al., 2010). All of these studies focused on established, long-term partnerships. Another research program, in collaboration with Gul Gunaydin, has focused on understanding factors influencing relationship formation and mate selection (e.g., Gunaydin, Selcuk, & Hazan, 2013; Gunaydin, Selcuk, Yilmaz, & Hazan, 2018; Gunaydin, Selcuk, & Zayas, 2017; Gunaydin, Zayas, Selcuk, & Hazan, 2012).  Although the majority of research projects I have been involved in focused on romantic or family relationships, work in collaboration with Omri Gillath examined how adults manage their broader social networks including friendships (Gillath, Johnson, Selcuk, & Teel, 2011; Gillath, Karantzas, & Selcuk, 2017). Finally, in recent studies my colleagues and I have started investigating factors influencing well-being in daily life. (Bayraktaroglu, Gunaydin, Selcuk, & Ong, 2019; Gunaydin, Selcuk, & Ong, 2016).