We present the results of an experiment that attempts to measure the social value of groups. In the experiment, group membership is induced artificially: subjects interact with insiders and outsiders in trust games and periodically enter markets where they can trade group membership. We find that trust falls with groups because of negative discrimination against outsiders. Against this, however, there is evidence that group membership provides a psychological benefit, albeit one that may induce social inertia. Overall, the welfare effects of groups are at best neutral and could be negative. (JEL: D17, Z13)

We test the portability of level-0 assumptions in level-k theory in an experimental investigation of behavior in Coordination, Discoordination, and Hide and Seek games with common, non-neutral frames. Assuming that level-0 behavior depends only on the frame, we derive hypotheses that are independent of prior assumptions about salience. Those hypotheses are not confirmed. Our findings contrast with previous research which has fitted parameterized level-k models to Hide and Seek data. We show that, as a criterion of successful explanation, the existence of a plausible model that replicates the main patterns in these data has a high probability of false positives.