<P> <BR></P>
<P>We experimentally examine how group identity affects trust behavior in an investment game. In one treatment, group identity is induced purely by minimal groups. In other treatments, group members are additionally related by outcome interdependence established in a prior public goods game. Moving from the standard investment game (where no group identity is prompted) to minimal group identity to two-dimensional group identity, we find no significant differences in trust decisions. However, trust is significantly and positively correlated with contribution decisions, suggesting that "social" trust is behaviorally important.</P>