A preliminary study indicates that dads speak in the same tones with kids as they do adults.

(Photo: Martin Allinger/Shutterstock)

You've probably heard baby talk before—the simple, high-pitched speech parents use when talking to babies and toddlers. Researchers believe that when moms and dads speak parentese, as it's known, it helps their children learn language faster. A small new study, however, suggests that mothers and fathers might play somewhat different roles in that learning.

Researchers know quite a bit about parentese, better known as motherese or baby talk. It's simpler than adult speech, both in terms of vocabulary and syntax. People speak baby talk in a higher tone of voice, though that tone varies more than normal adult speech.

The tone is higher for mothers, that is. Researchers don't actually know that much about how dads speak to their kids, and most of what's known about mothers comes from lab studies that might not reflect real-world circumstances.

Unlike moms' speech, dads spoke to their kids in the same tones and with the same variation in tone as they used when speaking to grown ups.

To get a better idea, Mark VanDam, Paul De Palma, and William Strong of Washington State University's Speech and Language Lab outfitted 11 toddlers with compact, lightweight audio recorders, which the kids kept in their chest pockets. The researchers used those recorders to collect 150 hours of audio, which included essentially everything a child heard on a typical day. Using software from the LENA Research Foundation, VanDam, De Palma, and Strong separated clips corresponding to mothers and fathers speaking to their kids and to other adults. They next analyzed those clips for two basic features: the average frequency of moms' and dads' speech, and the variation in that frequency.

Mothers fit the pattern that language development researchers have come to expect. On average, moms spoke to their kids in higher tones than they used with other adults, and they spoke to their kids in a wider range of tones than with adults. The story couldn't have been more different for fathers. Unlike moms' speech, dads spoke to their kids in the same tones and with the same variation in tone as they used when speaking to grown ups.

Those initial findings may support the so-called bridge hypothesis. First developed in the 1970s, the hypothesis suggests that mothers' higher-pitched speech and simple sentence structure helps infants develop early language skills faster, while fathers' generally lower intonation and more complex syntax forms a bridge between early skills and more adult syntax, vocabulary, and tones.

The new study has a number of limitations, however, chief among them the very small number of families who participated—something the researchers hope to resolve with 20,000 hours of family recordings they have yet to analyze. A more serious limitation may be that the study focused entirely on families with one mother and one father, leaving open questions about how parental speech plays out in single-parent families or families with two same-sex parents.

VanDam and colleagues presented the research yesterday at the Spring 2015 meeting of the Acoustical Society of America.

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