The Infant-Directed Vocal Communication in a Sheep Model

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Streaming Media

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neuroscience, vocal communication, infant-directed speech, adult-directed speech, infant-directed vocalization, adult-directed vocalization, sheep models


Integrative Systems Neuroscience Seminar Series


Human interactions with infants often involve a style of speaking referred to as infant-directed speech (IDS). Compared with adult-directed speech (ADS), IDS is characterized by a slower rate, more significant variations in fundamental frequency, long vowels and pauses, and increased repetition. Infants prefer listening to IDS in both their native language, as well as foreign languages, within days after birth. The evolutionary origin of IDS has remained an enigma for centuries. If the use of IDS in humans has its evolutionary origin, we predict that a special style of vocalization, namely infant-directed vocalization (IDV), which differs from adult-directed vocalization (ADV), should also be observable in non-human, even non-primate species. Vocal communication between adult female sheep (ADV), and vocal communication between ewes and lambs were recorded (IDV). The analysis of the sound characteristics showed a significant difference between ADV and IDV. The machine learning program could recognize the ADV and IDV with more than 90% accuracy. After performing the Fourier transforms, the ADV showed more dominant frequencies, which is believed to be the significant characteristics that ADV differs from IDV. The recordings of their mothers' ADV and IDV then played for the pre-weaning lambs. The observation showed the lambs moved towards the sound source more when IDV was played. And it is excellent in an outdoor environment. The lambs bleat back to their mothers' IDV more than to the ADV in the outdoor environment. These results proved that the IDV does exist in sheep species. The way the adult female sheep communicate with their offspring is different from their regular vocal communication. The lambs can distinguish the ADV and IDV and respond differently.


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