Overheard, baby edition: Making sense of new words

baby reading

Clever babies listen to your conversations and use the words they know to figure out new ones, a new study suggests. 


Babies are born into a foreign land where the customs are strange, the inhabitants confusing and the language utterly incomprehensible. But their minds are primed to slurp up information about their world, and this weird, frightening place soon turns familiar. Now, scientists have figured out one of babies’ tricks for learning new words.

It turns out that babies go fishing with familiar verbs (eat, cry, dance) to ferret out the meaning of unknown nouns. For a study published in the April Cognition, Brock Ferguson of Northwestern University in Evanston, Ill. and colleagues showed 30 19-month-old babies pictures of two strange things: one exotic animal that the babies probably hadn’t seen, such as a hedgehog, and one abstract object, such as a sculpture.

After the two images disappeared, the babies then heard a recording of a conversation between two adults talking about the exotic animal, but with a nonsense name, calling a hedgehog a “dax,” for instance. Sometimes, the conversation would contain a verb that applies only to a living creature: “The dax is crying.” Other times, the sentence would be vague: “The dax is right here.”

After this discussion, the two images reappeared. If 19-month-olds had just overheard a conversation that used a familiar, informative verb, they spent more time looking at the animal, the researchers found. These babies knew that living things, not sculptures, cried, and therefore the dax must be the picture of the animal.

Fifteen-month-old babies weren’t able to make this logic leap. It could be that these youngsters haven’t yet learned that some verbs are more exclusive than others (that only living things cry and eat, for instance). Or perhaps 15-month-olds can do the same trick, but it just takes them much longer, the researchers suggest. There’s a lot of mental work happening behind the scenes here. The babies must call up the meaning of “cry,” remember that it only applies to living creatures, and simultaneously learn a totally new word. It’s pretty amazing when you think about it.

This study is a great reminder that babies don’t just learn words when someone shoves Snoopy in their face and says, “Dog!” Give babies more credit than that. These little foreigners are gleaning new tidbits from conversations constantly, even conversations that they’re not a part of.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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