Why do some (and only some) observations prompt people to ask “why?” We proposea functional approach to “Explanation-Seeking Curiosity” (ESC): the state that motivates people to seek an explanation. If ESC tends to prompt explanation search when doing so is likely to be beneficial, we can use prior work on the functional consequences of explanation search to derive “forward-looking” candidate triggers of ESC—those that concern expectations about the downstream consequences of pursuing explanation search. Across three studies (N = 877), we test hypotheses derived from this functional approach. In Studies 1-3, we find that ESC is most strongly predicted by expectations about future learningand future utility. We also find thatjudgments of novelty, surprise, and information gap predict ESC,consistent with prior work on curiosity; however, the role for forward-looking considerations is not reducible to these factors. In Studies 2-3, we findthat predictors of ESCform three clusters, expectations about learning(about the target of explanation), expectations aboutexport (to other cases and future contexts), and backward-looking considerations (having to do with the relationship between the target of explanation and prior knowledge). Additionally, these clusters are consistent across stimulus sets that probe ESC,but not fact-seeking curiosity.These findings suggest that explanation-seeking curiosity is aroused in a systematic way, and that people are not only sensitive to the match or mismatch between a given stimulus and their current or former beliefs, but to how they expect an explanation for that stimulus to improve their epistemic state.