Relationship Closeness Inventory

Berscheid, E., Snyder, M., & Omoto, A. M. (1989). The Relationship Closeness Inventory: Assessing the closeness of interpersonal relationships. Journal of Personality and Social Psychology, 57(5), 792-792-807

with measurement in this paper

 high  interdependence
A high degree of interdependence between two people is revealed in four properties of their interconnected activities: (1) the individuals have frequent impact on each other; (2) the degree of impact per each occurrence is strong; (3) the impact involves diverse kinds of activities for each person; and (4) all of these properties characterize the interconnected activity series for a relatively long duration of time. (Kelley et al., 1983, p. 13)