What’s worth talking about? Information theory reveals how children balance informativeness and ease of production

Of all the things we could say, what determines what is worth saying? Greenfield’s principle of informativeness states that, right from the onset of language, humans selectively comment on whatever they find unexpected. We quantify this tendency using information theoretic measures, and test the counterintuitive prediction that children will produce words that are low frequency given the context because these will be most informative. Using corpora of child directed speech, we identified adjectives that varied in how informative (i.e., unexpected) they were given the noun they modified. Three-year-olds (N=31, replication N=13) heard an experimenter use these adjectives to describe pictures. The children’s task was then to describe the pictures to another person. As the information content of the experimenter’s adjective increased, so did children’s tendency to comment on the feature that adjective had encoded. Furthermore, our analyses suggest that children balance this informativeness with a competing drive to ease production.