Two experiments investigated children's and adults' initial mapping of verb meanings.In Experiment 1, subjects were asked to use a newly learned verb to label events in which the instrument, action, or result was different from the events used to teach the verbs. All subjects showed a bias to interpret the result as the most important component of the novel verbs' meanings, and this bias increased with age. In Experiment 2, either the instrument, action, or result of events was varied during training to test subjects' ability to override their default biases. When results were varied in training, 5-year-olds and adults, but not 3-year-olds, were more likely to use the novel verb to label an event in which the result was changed again.When results were varied in training, all subjects were less likely to use the novel verb to label an event in which the action was changed. These findings suggest that there is a default rule hierarchy for learning novel verbs, and that both default rules and the ability to override these rules when presented with conflicting information about the meaning of a verb are still developing during preschool.