Two experiments investigated how preschoolers judge whether learning has occurred. Experiment 1 showed that 3- and 4-year-olds used an individual's ability to demonstrate knowledge to judge whether he/she had learned something, regardless of that individual's claim about whether he/she had learned. Experiment 2 considered whether children responded based on just the character's demonstrative ability or whether children integrate various pieces of mental state knowledge to make a judgment about learning. Using a similar procedure, preschoolers were first told that the character claimed to be ignorant and then that they learned or did not learn a piece of information. In these cases, judgments of learning changed when the characters' claims and demonstrative abilities conflicted. These results suggest that children's understanding of learning involves the integration of various pieces of mental state knowledge. This process starts in the preschool years, but these data also suggest that crucial developments are taking place after age 4.