Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We report results from an Ultimatum Game experiment with and without pre-play communication, conducted both in a real-world experimental laboratory and in the virtual world Second Life. In the laboratory, we replicate previous results that communication increases offers and agreement rates significantly, and more so for face-to-face communication than for text-chat. In Second Life we detect a level shift to more cooperation when there is no communication, either driven by selection on unobservables or environmental effects. The higher cooperativeness in the virtual world lowers the need for additional communication between avatars in order to achieve efficient outcomes. Consistent with this we are not able to detect an effect of allowing avatar-to-avatar communication.