Pitch characteristics of infant-directed speech affect infants' ability to discriminate vowels.

"Baby talk" or speech directed to prelinguistic infants is high in pitch and has exaggerated pitch contours (up/down patterns of pitch change) across languages and cultures. Using an acoustic model, we predicted that the large pitch contours of infant-directed speech should improve infants' ability to discriminate vowels. On the other hand, the same model predicted that high pitch would not benefit, and might actually impair, infants' ability to discriminate vowels. We then confirmed these predictions experimentally. We conclude that the exaggerated pitch contours of infant-directed speech aid infants' acquisition of vowel categories but that the high pitch of infant-directed speech must serve another function, such as attracting infants' attention or aiding emotional communication.