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Function and evolution of vibrato-like frequency modulation in mammals

journal contribution
posted on 2023-06-09, 07:18 authored by Benjamin D Charlton, Anna M Taylor, David Reby
Why do distantly related mammals like sheep, giant pandas, and fur seals produce bleats that are characterized by vibrato-like fundamental frequency (F0) modulation? To answer this question, we used psychoacoustic tests and comparative analyses to investigate whether this distinctive vocal feature has evolved to improve the perception of formants, key acoustic components of animal calls that encode important information about the caller’s size and identity [1]. Psychoacoustic tests on humans confirmed that vibrato-like F0 modulation improves the ability of listeners to detect differences in the formant patterns of synthetic bleat-like stimuli. Subsequent phylogenetically controlled comparative analyses revealed that vibrato-like F0 modulation has evolved independently in six mammalian orders in vocal signals with relatively high F0 and, therefore, low spectral density (i.e., less harmonic overtones). We also found that mammals modulate the vibrato in these calls over greater frequency extents when the number of harmonic overtones per formant is low, suggesting that this is a mechanism to improve formant perception in calls with low spectral density. Our findings constitute the first evidence that formant perception in non-speech sounds is improved by fundamental frequency modulation and provide a mechanism for the convergent evolution of bleat-like calls in mammals. They also indicate that selection pressures for animals to transmit important information encoded by formant frequencies (on size and identity, for example) are likely to have been a key driver in the evolution of mammal vocal diversity.

History

Publication status

  • Published

File Version

  • Accepted version

Journal

Current Biology

ISSN

0960-9822

Publisher

Elsevier

Issue

17

Volume

27

Page range

2692-2697

Department affiliated with

  • Psychology Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2017-07-20

First Open Access (FOA) Date

2018-09-11

First Compliant Deposit (FCD) Date

2017-07-20

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