Spontaneous Motor Entrainment to Music in Multiple Vocal Mimicking Species

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Sample videos of birds entrained to music

Download the YouTube videos analyzed in the Current Biology paper

Whether in a military march, an urban club or a tribal dance ritual, humans spontaneously synchronize their movements to auditory beats, a phenomenon termed entrainment. Other primates do not appear to share this ability. However, our work suggests that entrainment is not a uniquely human capacity, as previously believed. We find strong evidence of entrainment in multiple species of parrot.

Both parrots and humans are proficient vocal mimics (able to imitate sound), while non-human primates and most animals in contact with humans are not. This is consistent with the hypothesis put forward by Patel (2006) that entrainment emerged as a byproduct of selection for vocal mimicry. If this were the case, vocal mimicry would be a necessary precondition for entrainment, and we should only find entrainment in vocal mimicking species.

We tested the hypothesis that vocal mimicry is necessary for entrainment by systematically querying an internet video database for evidence of entrainment in both vocal mimics and vocal non-mimics, sampling a wide variety of birds and mammals. Across thousands of videos and hundreds of species, only vocal mimics showed evidence of entrainment, in spite of the high representation of vocal non-mimics in the database and comparable exposure to both humans and music. We conclude that entrainment is not unique to humans, and may have evolved as a by-product of selection for vocal mimicry.

Infant-directed speech

When speaking to infants, adults in all cultures modify their speech to have a higher pitch, greater pitch variability, slower speed, and longer pauses. Our research suggests that young infants' social preferences can be modified by the presence or absence of infant-directed speech. We suggest that infants encode the appropriateness of vocal behavior and use that information to guide subsequent preference for individual social partners, an ability that may serve as an important foundation for social reasoning.