Strategizing under Rule and Vote Uncertainty: An Experiment

In a controlled laboratory experiment, we examine voting behavior under rule uncertainty, i.e., uncertainty about the voting rule itself. We compare behavior under three voting-rule conditions: simple plurality (1R), plurality with runoff (2R), and their probabilistic mixture (1R/2R) that is a lottery generating either 1R with known probability p, or 2R with probability 1-p. Following the previous literature, we conjecture that 1R/2R raises computational complexity and thus mitigates strategic manipulation. We test different models – either heuristic-based or rational – of (i) the formation of beliefs about other voters’ behavior, and of (ii) the resulting voting decisions. We find that beliefs tend to be formed in a myopic manner in all experimental conditions. With repetition, however, the accuracy of the belief formation process improves and we observe convergence between beliefs and votes. Regarding voting decisions, the model with highest (resp., lowest) predictive power is strategic (resp., sincere) voting, with some variation across conditions. Overall, our initial conjecture is not supported by the experimental data. Rule uncertainty steers the voters neither towards sincerity nor towards any other voting heuristic. If anything, it contributes to promoting strategic behavior.