Although the study of the effects of voting systems started before Maurice Duverger, credit goes to him for systematizing the analysis and for making a clear distinction between the mechanical effects of voting systems, i.e., the conversion of votes into seats, and the psychological effects of voting systems, i.e., the tendency of voters to anticipate the mechanical effects of electoral rules and to adapt their behaviors to each party?s chances of winning in order to maximize the utility of their vote. According to Duverger, plurality rules favor tactical voting. However, in the cases of proportional representation (PR) and the majority runoff rule, he argues that these electoral systems generate no incentive to vote tactically. These assumptions have been empirically tested in laboratory experiments of a type that was not long ago the preserve of the hard sciences but that are no longer unfamiliar to the social sciences, including political science. This paper first describes our experimental protocol. We then give details of our experimental results. In conclusion, we use our experimental results to illustrate the overall benefits of the experimental approach in understanding the psychological effects of voting systems.