Noise hampers children's expressive word learning

Purpose: To determine the effects of noise and speech style on word learning in typically developing school-age children. Method: Thirty-one participants ages 9;0 (years;months) to 10;11 attempted to learn 2 sets of 8 novel words and their referents. They heard all of the words 13 times each within meaningful narrative discourse. Signal-to-noise ratio (noise vs. quiet) and speech style (plain vs. clear) were manipulated such that half of the children heard the new words in broadband white noise and half heard them in quiet; within those conditions, each child heard one set of words produced in a plain speech style and another set in a clear speech style. Results: Children who were trained in quiet learned to produce the word forms more accurately than those who were trained in noise. Clear speech resulted in more accurate word form productions than plain speech, whether the children had learned in noise or quiet. Learning from clear speech in noise and plain speech in quiet produced comparable results. Conclusion: Noise limits expressive vocabulary growth in children, reducing the quality of word form representation in the lexicon. Clear speech input can aid expressive vocabulary growth in children, even in noisy environments.