In many collective decision making situations, agents use voting to choose an alternative that best represents the preferences of the group. It is often assumed that voters will vote truthfully rather than expending the effort needed to manipulate the outcome in cognitively and computationally complex situations. However, being truthful is just one possible heuristic that agents may employ. We examine how real voters employ heuristics in a variety of approval voting scenarios. In particular, we consider heuristics where a voter ignores information about other voting profiles and makes their decisions based solely on how much they like each candidate. In a behavioral experiment, we show that people vote truthfully in some situations, but prioritize high utility candidates in others. We show how the structure of the voting environment affects how well each heuristic performs as well as how and when humans employ these different heuristics.