People can learn about the effects of their actions either by performing physical experiments or by running mental sim- ulations. Physical experiments are reliable but risky; mental simulations are unreliable but safe. We investigate how peo- ple negotiate the balance between these strategies. Participants attempted to shoot a ball at a target, and could pay to take practice shots (physical experiments). They could also simply think (run mental simulations), but were incentivized to act quickly by paying for time. We demonstrate that the amount of thinking time and physical experiments is sensitive to trial characteristics in a way that is consistent with a model that integrates information across simulation and experimentation and decides online when to perform each.