Nezlek, J. B. (1995). Social construction, gender/sex similarity, and social interaction in close personal relationships. Journal of Social and Personal Relationships, 12, 503-520.

Participants maintained a social interaction diary, a variant of the Rochester Interaction Record, to describe their close personal relationships. Relationships were defined using relative frequency of contact with different individuals and via participants' descriptions of relational partners. Individuals with whom participants had more contact were more likely to be described as close friends than were individuals with whom participants had less contact. The results suggest that the characteristics of same-sex relationships depend less on the specific partners comprising the relationship than do the characteristics of opposite-sex relationships. As hypothesized, the characteristics of close same-sex relationships did not differ from the characteristics of other same-sex relationships, although interactions with best friends were more intimate than interactions with other same-sex partners. In contrast, the characteristics of close opposite-sex relationships differed from the characteristics of other opposite-sex relationships. Men and women who were romantically involved had more contact with their romantic partners than with other opposite-sex persons, and they had more contact with their romantic partners than men and women who were not romantically involved had with their most frequent opposite-sex interaction partner. For women, interactions with most frequent opposite-sex interaction partners were more affectively rewarding and instrumentally positive if these men were romantic partners, whereas for men, the affective quality and instrumentality of interactions with most frequent opposite-sex interaction partners did not differ as function of whether these women were romantic partners.