  Understanding the dynamics of reciprocation is of great interest in sociology
and computational social science. The recent growth of Massively Multi-player
Online Games (MMOGs) has provided unprecedented access to large-scale data
which enables us to study such complex human behavior in a more systematic
manner. In this paper, we consider three different networks in the EverQuest2
game: chat, trade, and trust. The chat network has the highest level of
reciprocation (33%) because there are essentially no barriers to it. The trade
network has a lower rate of reciprocation (27%) because it has the obvious
barrier of requiring more goods or money for exchange; morever, there is no
clear benefit to returning a trade link except in terms of social connections.
The trust network has the lowest reciprocation (14%) because this equates to
sharing certain within-game assets such as weapons, and so there is a high
barrier for such connections because they require faith in the players that are
granted such high access. In general, we observe that reciprocation rate is
inversely related to the barrier level in these networks. We also note that
reciprocation has connections across the heterogeneous networks. Our
experiments indicate that players make use of the medium-barrier reciprocations
to strengthen a relationship. We hypothesize that lower-barrier interactions
are an important component to predicting higher-barrier ones. We verify our
hypothesis using predictive models for trust reciprocations using features from
trade interactions. Using the number of trades (both before and after the
initial trust link) boosts our ability to predict if the trust will be
reciprocated up to 11% with respect to the AUC.
