The cognitive significance of being in a close relationship is described in terms of including other in the self (in Lewin's sense of overlapping regions of the life space and in James's sense of the self as resources, perspectives, and characteristics). Experiment 1, adapting Liebrand's (1984) decomposed-game procedures, found less self/other difference in allocations of money to a friend than to a stranger, regardless of whether Ss expected other to know their allocations. Experiment 2, adapting Lord's (1987) procedures, found that Ss recalled fewer nouns previously imaged with self or mother than nouns imaged with a nonclose other, suggesting that mother was processed more like self than a stranger. Experiment 3, adapting self-schema, reaction-time procedures (e.g., Markus, 1977), found longer latencies when making “me/not me” decisions for traits that were different between self and spouse versus traits that were similar for both, suggesting a self/other confusion with spouse.

During the 1980s, close-relationship research expanded rapidly, rating its own Handbook (Duck, 1988) and its own Annual Review of Psychology chapter (Clark & Reis, 1988). Much of the research in this area does not explicitly define what is meant by a close relationship. However, the behavioral, systemic definition offered by Kelley et al. (1983) has been widely influential. It focuses on mutual influence, interdependence, and degree of interconnectedness of activities. This approach recently served as the basis for the development of a measure of interpersonalcloseness behavior (Berscheid, Snyder, & Omoto, 1989a, 1989b), which focuses on time spent together, diversity of shared activities, and perceived influence of other over one's own decisions. (Maxwell, 1985, also developed a behavioral measure of closeness, which is based on a more general review of the closerelationship literature.)

There has been much less consensus about the cognitive significance of such behavioral interdependence for each person in a close relationship. Yet a number of relevant phenomena have been observed,...