Understanding knowledge acquisition involves a comprehension of the relationship between a person's access to relevant information and that person's subsequent knowledge. This report investigates how preschoolers improve in their ability to evaluate the effects of two distinct types of messages—ambiguous and informative—on a listener's knowledge. Three- and four-year olds were pre- and posttested for their ability to judge message quality from a third-person perspective. Between sessions, children were assigned to one of three training conditions. In all conditions, children observed a speaker providing ambiguous messages and informative messages to a listener. In the general-feedback condition, children were informed as to whether the listener gained knowledge after each message. In the specific-feedback condition, children were informed as to whether, as well as why, the listener gained knowledge. In the no-feedback condition, children were not informed as to the listener's state of knowledge. Children in the specific-feedback condition improved their ability to judge messages, and children in the general- feedback condition showed a marginally significant improvement. No learning effects, however, were observed in a transfer task for any of the groups. Results suggest that informing preschoolers about message quality during conversational exchanges contributes to their developing understanding of how people acquire knowledge about the world.