Research reveals how adults understand what kids are saying

Research reveals how adults understand what kids are saying
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Cambridge, UK: When babies first start talking, their vocabulary is extremely limited. One of the first sounds babies make is "da," which could mean dad, a dog, a dot, or nothing at all.

How does an adult listener make sense of this limited verbal repertoire? A new study from MIT and Harvard University researchers has found that adults' understanding of conversational context and knowledge of mispronunciations that children commonly make are critical to the ability to understand children's early linguistic efforts.

Using thousands of hours of transcribed audio recordings of children and adults interacting, the research team created computational models that let them start to reverse engineer how adults interpret what small children are saying. Models based on only the actual sounds children produced in their speech did a relatively poor job predicting what adults thought children said. The most successful models made their predictions based on large swaths of preceding conversations that provided context for what the children were saying. The models also performed better when they were retrained on large datasets of adults and children interacting.

The findings suggest that adults are highly skilled at making these context-based interpretations, which may provide crucial feedback that helps babies acquire language, the researchers say.

"An adult with lots of listening experience is bringing to bear extremely sophisticated mechanisms of language understanding, and that is clearly what underlies the ability to understand what young children say," says Roger Levy, a professor of brain and cognitive sciences at MIT. "At this point, we don't have direct evidence that those mechanisms are directly facilitating the bootstrapping of language acquisition in young children, but I think it's plausible to hypothesize that they are making the bootstrapping more effective and smoothing the path to successful language acquisition by children."

Levy and Elika Bergelson, an associate professor of psychology at Harvard, are the senior authors of the study, which appears today in Nature Human Behavior. MIT postdoc Stephan Meylan is the lead author of the paper.

Adult listening skills are critical

While many studies have investigated how children learn to speak, in this project, the researchers wanted to flip the question and study how adults interpret what children say.

"While people have looked historically at a number of features of the learner, and what is it about the child that allows them to learn things from the world, very little has been done to look at how they are understood and how that might influence the process of language acquisition," Meylan says.

Previous research has shown that when adults speak to each other, they use their beliefs about how other people are likely to talk, and what they're likely to talk about, to help them understand what their conversational partner is saying. This strategy, known as "noisy channel listening," makes it easier for adults to handle the complex task of deciphering the acoustic sounds they're hearing, especially in environments where voices are muffled or there is a lot of background noise, or when speakers have different accents.

In this study, the researchers explored whether adults can also apply this technique to parsing the often seemingly nonsensical utterances produced by children who are learning to talk.