Infants learn to speak by listening to words that are spoken by those around them. As infants listen and learn words, they don’t hear the words repeated the same way every time. In everyday speech, we say the same words with variations in pitch, duration, and other acoustic properties. Dr. Elika Bergelson, a recipient of the High-Risk, High-Reward Research Program’s Early Independence Award, is studying how infants’ daily experiences and exposures contribute to word learning and affect development. Dr. Bergelson published a study with Dr. Federica Bulgarelli investigating which acoustic properties had the most impact on how infants learn and say words for the first time. 

In the study, Dr. Bergelson and Dr. Bulgarelli used a database of one-hour home audio recordings of 6- to 17-month-old infants over the course of a year. They used these recordings to analyze the acoustic properties and frequency of common words such as “ball,” “baby,” “water,” and “dog.” The researchers noted when these words were spoken and tracked how old the infants were when they first said these words. The researchers found that the more often words were repeated and with greater acoustic variability of those words, infants were more likely to say that word earlier in their speech development. In addition, children were inclined to say words sooner if those words were said directly to the children rather than being part of a conversation between adults the infants could hear. These results suggest that variation in acoustics may shape how an infant expects a word to sound, and that having a broader range of reference sounds may impact how soon the infant tries to say the word themselves. As this study only used audio recordings from English-speaking, monolingual households with young infants, more work remains to understand how applicable these results are across different languages and for larger groups of speakers of different ages. 

Reference: Bulgarelli F, Bergelson E. Linking acoustic variability in the infants' input to their early word production. Dev Sci. 2024 Jul 8:e13545. doi: 10.1111/desc.13545. Epub ahead of print.