How do voting institutions affect incentives of committees to vote for ethical alternatives? We model the problem of a committee, whose members have different depths of reasoning, that decides whether to approve an ethical proposal. Members who vote for the proposal receive expressive utility, but all members pay a cost if the proposal is passed. The model suggests that institutional features that reduce the probability of a member being pivotal – such as larger committee size, or a more restrictive majority rule – increase the expected share of votes in favour of the ethical alternative. A laboratory experiment with a charitable donation framing demonstrates comparative statics that are in line with these results. We also structurally estimate the distribution of expressive preferences across individuals, and find that a high proportion of them are strategically naive.