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Some experts suggest the best way to teach language to a tiny baby is to speak as though the infant were another adult, since adult sounds, cadence, and tone of voice are what the child should eventually learn.

But researchers using a mathematical model discovered that it might actually be better to use “motherese,” a sing-song voice that exaggerates the sounds the baby hears.

“Our intuitions are surprisingly right,” says Patrick Shafto, associate professor of mathematics and computer science at Rutgers University. “Why do we speak funny to children? It’s actually to help them learn the relevant properties of language.”

For the study in Psychological Review, researchers deconstructed vowel sounds in adult speech and then created a mathematical model that predicted understandable speech patterns from scratch, “to show what it might look like if speech were designed to actually teach children.” They then compared their invented teaching pattern with the differing speech methods that adults direct at each other and at infants, and found that infant-directed speech was the closer match.

“The sounds that are selected exaggerate the important properties that babies need to attend to and learn about,” Shafto says. “If you exaggerate in the correct way, what you get is a learner who learns more quickly from less data.” It makes sense that over time the baby’s brain is then able to process the “motherese” into regular language.

Our other sing-song voices

The mathematical model is an elegant way to think about infants’ learning, but the work is preliminary. For instance, proving that infant-directed speech is more educational is difficult by definition because babies not even a year old are too young to speak, so it is challenging to probe any language skills they have learned.

But there may be a different group of learners who could demonstrate the value of the model. Shafto says American adults not only speak in exaggerated ways to babies, but also distort their speech with pets and foreign language speakers—but differently for each.

Pets hear sing-songy voices with no effort by the speaker to exaggerate vowels to make the animals understand—a pure play to cuteness that differs from speech intended to teach a baby. Foreigners get the opposite—no condescending sing-song, but a concerted effort to exaggerate vowel sounds—the better to help the listener understand a language he or she may not know.

Because foreign-language speakers’ learning of English can be measured, it might be possible to use mathematics to fine tune the speech patterns of instructors in ways that enhance the teaching of English as a second language. “By manipulating only the things that are important and highlighting the meaningful distinctions in the language,” Shafto says, “we might be able to make English more learnable for someone who speaks a different language natively.”

The bottom line is that math and the study of language learning go extremely well together. “Learning these vowel categories is a complicated problem,” Shafto says. “There are lots of moving parts, so it’s not the sort of thing that one can easily intuit. I think it’s a nice example of why mathematical rigor is important in areas where you least expect it.”

Source: Rutgers University