One way to learn about the world is by asking questions. We investigate how children (n= 287, 7- to 11-year olds) and young adults (n=160 17- to 18-year olds) ask questions to identify the cause of an event. We find a developmental shift in children’s reliance on hypothesis-scanning questions (which test hypotheses directly) versus constraint-seeking questions (which reduce the space of hypotheses), but also that all age groups ask more constraint-seeking questions when hypothesis-scanning questions are unlikely to pay off: when the problem is difficult (Studies 1 and 2) or the solution is one among equally likely alternatives (Study 2). These findings are the first to demonstrate that even young children adapt their strategies for inquiry to increase the efficiency of information search.