How do voting institutions affect incentives of committees to vote expressively? We model a committee that chooses whether to approve a proposal that some members may consider ethical. Members who vote for the proposal receive expressive utility, and all members pay a cost if the proposal is accepted. Committee members may have different depths of reasoning. Under certain sufficient conditions, the model predicts that features that reduce the probability of a member being pivotal – namely, larger committee size, or a more restrictive voting rule – raise the share of votes in favour of the proposal. A laboratory experiment with a charitable donation framing presents evidence in line with these results. Our structural estimation recovers the distributions of altruistic and expressive preferences, as well as of depth of reasoning, across individuals.