CLOSE RELATIONSHIPS 19
she notes that friends become “real experts on one another. They know about each other’s backgrounds,
habits, present lives, future plans, particular experiences, people they know and so on” (p. 349). Others
have also argued that increased interaction, being present in the same environment, and participating in
joint experiences leads to the creation of uniquely shared mutual knowledge (Clark & Marshall, 1981;
Krauss & Fussell, 1991). Again, we argue that this precious resource (i.e., mutually shared knowledge)
can be called upon to solve subsequent complex coordination problems, ultimately making it easier for
friends to reap the benefits of non-zero sum outcomes. We speculate that creating highly idiosyncratic
mutual knowledge with a partner underlies the feeling of being understood, an important indicator of
intimacy and relational satisfaction (Reis & Shaver, 1988). Specifically, we believe that feeling
understood occurs as a result of partners being able to resolve complex coordination problems efficiently.
Again, this does not mean that individuals should be able to articulate their mutual beliefs with a high
degree of precision – we believe that most mutual knowledge is tacitly acquired and covertly used (for
similar argument about communicative processes, in general, see Kellermann, 1992). From the
perspective taken here, implicit mutual knowledge is critical for solving coordination problems while the
ability to articulate such knowledge is considerably less important.
Finally, the creation of idiosyncratic mutual knowledge may help resolve the Banker’s Paradox.
When individuals in highly interdependent relationships create extensive mutual knowledge, this
knowledge becomes a vital resource that can be exploited when solving complex coordination problems,
ultimately leading to the creation of substantial non-zero sum gains. As such, friends become
indispensable, not because of who they are, but because of what they know and more importantly because
of how this knowledge can be put to use for self-gain. From an evolutionary perspective, it would be in
one’s self-interest to lend considerable assistance to a friend in dire need, not based on the expectation
that friends will eventually reciprocate such favors (Clark & Mills, 1993; Tooby & Cosmides, 1996), but
as a means of protecting a precious resource. This resource just happens to reside in the mutual
knowledge that we share with a close friend.
Evidence with respect to Development and Maintenance. The claims underlying our model are
consistent with research demonstrating that relational development is centered around social exchange
and that this process tends to be fast and furious in nature (see for review, Berg & McQuinn, 1986).
Additionally, the ideas proposed here coincide with research indicating that reciprocity plays an important
role in close relationships throughout their lifespan (see, for review, Buunk & Prins, 1998) – even when a
partner is facing a serious illness reciprocal exchange is still expected (Kuijer, Buunk, & Ybema, 2001;
Ybema, Kuijer, Hagedoorn, & Buunk, 2002). Our model also attempts to bridge the gap between
scholars who believe that close relationships are based on communal rules of providing assistance (Clark
& Mills, 1993) and those who believe that resource exchange is primarily driven by concerns for
Convention