Communication and punishment in voluntary contribution experiments

We compare three forms of communication and punishment as incentives to increase contributions to public goods in laboratory experiments. We find, as in earlier experiments, that face-to-face communication has very strong effects, but surprisingly that verbal communication through a chat room preserving anonymity and excluding facial expression, etc. was almost as efficient. Numerical communication, via computer terminals, had no net effect on contributions or efficiency. Punishment, as in earlier experiments, increased contributions but because of its cost had little net effect on efficiency.