Researchers from UCLA recorded eight American, native English-speaking mothers speaking in various intonations to both adults and children, then played the recordings to 26 male and female members of a nonindustrialized culture in South America called the Shuar. The mothers were asked to react verbally to photographs of babies and adults engaged in various activities comprising four categories: prohibitive, approval, comfort and attention.
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"The Shuar are quite distant from European languages such as English, and because they're culturally isolated it provides a good test," says Greg Bryant, assistant professor in the communication studies department at UCLA and lead author of the study. (It appears in this month's issue of the journal Psychological Science.) The Shuar live in small hunting-gardening communities in Ecuador.
One reason those higher tones are preserved for the crawling set: "Babies have immature perceptual systems, and they need extra enhanced input. So you're spoon feeding them, essentially, which helps them understand," Bryant says.
With exaggerated sound effects, he adds, "you get enhanced perception. When people talk to adults, they rely more on words."
-- Jeannine Stein