We introduce a novel method to test a classic idea in developmental science that children's attention to a stimulus is driven by how much they can learn from it. Preschoolers (4-6 years, M=4.6) watched a video where a distracting animation accompanied static, page-by-page illustrations of a storybook. The audio narration for each storybook page was looped so that children could listen to it up to six times in total. However, the narration automatically ended if the child looked at the distractor for an extended period of time, indicating their loss of attention to the story, and triggering the next page. The complexity of the narration was manipulated between-subjects: The "Simple" narration largely contained words that should be familiar to preschoolers, while the "Complex" narration contained many rare, late-acquired words. Children's learning was measured via post-tests of their plot comprehension and ability to generalize the embedded rare words. Consistent with the hypothesis that children's attention was driven at least partly by their ability to learn from the speech, we observed a significant interaction between narration complexity and age in predicting children's probability of continuing listening on each page, and the proportion of their visual attention that they devoted to the story illustration, over the animated distractor. That is, while younger children were more likely to continue listening to the "Simple" speech, older children became increasingly likely to sustain attention to the "Complex" speech. Our results provide evidence that young children may actively direct their attention toward linguistic input that is most appropriate for their current level of cognitive and linguistic development, which may provide the best learning opportunities.