The scope of audience design in child-directed speech: Parents' tailoring of word lengths for adult versus child listeners.

When communicating with other people, adults reduce or lengthen words based on their predictability, frequency, and discourse status. But younger listeners have less experience than older listeners in processing speech variation across time. In 2 experiments, we tested whether English-speaking parents reduce word durations differently across utterances in child-directed speech (CDS) versus adult-directed speech (ADS).