Voting games and computational complexity

Voting rules over three or more alternatives suffer from a general problem of manipulability. However, if the rule is 'difficult' to manipulate, in some formal computational sense that is intrinsic to the rule or some cognitive sense specific to the set of voters, then one might not observe manipulation in practice. We evaluate this hypothesis using controlled laboratory experiments. We conclude that one voting rule, due originally to Condorcet, is indeed behaviorally incentive-compatible despite being theoretically manipulable if the underlying preference environment is sufficiently diverse that voters have difficulty ascertaining others' preferences. Copyright 2008 , Oxford University Press.