Babies, like tiny feral animals, learn with their mouths. It’s one of the earliest forms of problem-solving: Does this hand/iPhone/Cheerio taste good? What’s its texture? What does it do?
But babies also use their mouths to learn even when they aren’t putting foreign objects into them. In a study published earlier this week in the journal Proceedings of the National Academy of Sciences, a team of audiology and psychology researchers from the University of British Columbia established the first direct link between babies’ oral motor skills—the movement of the tongue, lips, and other parts of the mouth—and their ability to understand speech.
The study authors played two different “d” sounds—both common in Hindi, but not found in English—for six-month-olds from English-speaking households. As the sounds played, some of the babies had teething toys in their mouths: either a hard toy that restricted the movement of the tongue, which would impede the ability to make a d sound, or a soft pacifier that went between the gums and left the tongue unaffected (the researchers ran ultrasounds of the babies’ mouths to confirm the effects of each toy).
What they found: The presence of a teething toy didn’t necessarily make a difference, but the type of toy did—babies whose tongues were constrained couldn’t distinguish between the sounds as well as the others.