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The Surprisingly Early Influence of Speech

“Up?” pleads the 13-month-old, reaching in the direction of her mother, who then sweeps the baby into her arms. For parents, our infants’ first one-word utterances feel like the magical entrance into a world in which infants can finally express their thoughts and understand ours. In the last decade, though, developmental psychologists have discovered that long before the first syllables escape an infant’s lips, language acquisition has begun. In a new article in Trends in Cognitive Sciences, the Project on Child Development’s Sandra Waxman and New York University’s Athena Vouloumanos review these exciting new discoveries. From the very beginning, they explain, acquiring language engages much more than language alone. In the first year of life, speech is powerfully linked with astonishing cognitive and social capacities that enable an infant to learn about their rapidly expanding world.

We now know that infants favor human speech more from birth than any other sound.  And though the infants prefer to listen to human speech, rhesus monkey calls light up similar areas of their brains during neural imaging in the first month of life. By 3 months, however, this initially broad template has been fine tuned, and different areas light up when they hear human speech and monkey calls. We also know that the babies don’t just prefer any familiar human sounds over those produced by monkeys: 3-month-olds prefer to listen to speech over other human vocalizations like laughing or sneezing.  Later on, individual differences in infants’ preferences for speech may even indicate discrepancies in social cognitive capacities; babies who show reduced preferences for human speech at 12 months display more autistic-like behaviors by 18 months.

From the onset, speech is also linked to surprisingly sophisticated social abilities. By 5 months, infants understand that human speech identifies potential communication partners. If you show them a monkey face and a human face, they match human speech with the human face and monkey calls to the monkey face. However, they’re not able to match other human sounds like laughter to the human face yet: once again, it’s clear that from the very beginning, speech is a privileged signal.

Not only do very young infants prefer speech and use it as a social cue, it also scaffolds cognitive development.  By 7 months, speech facilitates sophisticated cognitive abilities like learning abstract rules and patterns. Infants this age who hear two minutes of ABB-patterned speech sequences (e.g., la-ga-ga, da-li-li) will learn the rule and identify subsequent ABB patterns. If instead they hear two minutes of ABB non-speech sounds, though, such as musical tones or animal sounds, they are unable to learn the rule.  As we discussed in our previous blog entry, speech also accelerates young infants’ abilities to categorize objects, a significant cognitive step toward making sense of their world. Though they’re not even talking yet, infants learn better with speech.

Young babies are also aware that language is used to share information. As adults, if we witness two foreigners speaking to each other in a language that we can’t identify, we’re nonetheless aware that the conversational partners are communicating with each other. Surprisingly, even 6-month-old infants also understand this principle. In one study, an actor attempting to reach an object found that it was out of reach. When a second actor appeared, infants expected that if the two spoke to each other, the second actor would help the first reach the object. If instead the actor coughed or made other non-speech sounds, they had no such expectation. While it may seem extraordinary that infants who can’t yet speak understand that language transmits information, it’s easy to see how this early ability will enable rapid language growth and learning in the months that follow.

At our research centers, both at Northwestern and NYU, we have begun to uncover the astonishingly early link between language, thought, and social abilities. But we still have many questions to answer. We now know that a one-year-old is remarkably adept at learning about his world with the assistance of human speech, but does sign language work the same way? And how does learning more than one language impact the early link between language and thinking? We look forward to investigating these mysteries and many more in the years to come!