Sensitivity to over - informativeness 1 Running head : Sensitivity to over - informativeness Development of children ' s sensitivity to over - informativeness in learning and teaching

Effective communication requires knowing the “right” amount of information to provide; what is necessary for a naïve learner to arrive at a target hypothesis may be superfluous and inefficient for a knowledgeable learner. The current study examines fourto seven-year-olds’ developing sensitivity to over-informative communication and their ability to decide how much information is appropriate depending on the learner’s prior knowledge. In Experiment 1 (N=184, Age: 4.09– 7.98), children preferred teachers who gave costly, exhaustive demonstrations to naïve learners and efficient, selective demonstrations to knowledgeable learners who already had common ground with the teachers. While older children preferred different teachers depending on the learner’s prior knowledge, four-year-olds did not show a clear preference. In Experiment 2 (N=80, Age: 4.05 – 6.99), we asked whether children flexibly modulated their own teaching based on learners’ knowledge. Five and six-year-olds, but not four-year-olds, were more likely to provide exhaustive demonstrations to naïve learners than to knowledgeable learners. These results suggest that by age five, children are sensitive to over-informativeness and understand the trade-off between informativeness and efficiency; they reason about what others know based on the presence or absence of common ground and flexibly decide how much information is appropriate both as learners and as teachers.