p.1097 empirical examples of changing norms suggest that real people are more likely to use trial and error behavior than detailed calculations based on accurate beliefs about the future... I use an evolutionary approach. This approach is based on the principle that what works well for a player is more likely to be used again while what turns out poorly is more likely to be discarded (Axelrod, 1984)... In an evolutionary approach... there is no need to assume a rational calculation to identify the best strategy. Instead, the analysis of what is chosen at any specific time is based upon an operationalization of the idea that effective strategies are more likely to be retained than ineffective strategies. Moreover, the evolutionary approach allows the introduction of new strategies as occasional random mutations of old strategies.