Circadian preference and relationship satisfaction among three types of couples.

Mate selection is part of a growing interest in the study of processes by which couples are established, consolidated and/or separated. Similarity in psychological traits has been related to the well-being of couples, but given the possible effect of temporal convergence, it is necessary to control for the relationship length and whether or not both members of the couple live together. The aim of this study was to analyse the association between Morningness/Eveningness (M/E) similarity and relationship satisfaction in young-dating-non-cohabiting, young-married-cohabiting and old-married-cohabiting couples. Participants included 357 heterosexual couples (357 women and 357 men) with a mean age of 38.42 years old (SD = 13.11; age range between 19 and 69) who completed M/E (Composite Scale of Morningness) and relationship satisfaction measures (Comprehensive Marital Satisfaction Scale). Similarity in M/E was positively related to greater relationship satisfaction in both young cohabiting and non-cohabiting couples. In women, their own M/E was related to their own relationship satisfaction, whereas the level of relationship satisfaction in men was related to their partner's M/E. This relationship was observed in young-married-cohabiting couples. M/E similarity may operate differently as a function of the relationship stage.