Formant Modification through Vocal Production Learning in Gray Seals

• Published in: Current biology 2019-07, Vol.29 (13), p.2244-2249.e4
• Main Authors: Stansbury, Amanda L., Janik, Vincent M.
• Format: Article
• Language: English
• Subjects: animal cognition; animal communication; animal music; bioacoustics; Halichoerus grypus; pinnipeds; vocal learning
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2019.05.071

Vocal production learning is a rare communication skill and has only been found in selected avian and mammalian species [1–4]. Although humans use learned formants and voiceless sounds to encode most lexical information [5], evidence for vocal learning in other animals tends to focus on the modulation pattern of the fundamental frequency [3, 4]. Attempts to teach mammals to produce human speech sounds have largely been unsuccessful, most notably in extensive studies on great apes [5]. The limited evidence for formant copying in mammals raises the question whether advanced learned control over formant production is uniquely human. We show that gray seals (Halichoerus grypus) have the ability to match modulations in peak frequency patterns of call sequences or melodies by modifying the formants in their own calls, moving outside of their normal repertoire’s distribution of frequencies and even copying human vowel sounds. Seals also demonstrated enhanced auditory memory for call sequences by accurately copying sequential changes in peak frequency and the number of calls played to them. Our results demonstrate that formants can be influenced by vocal production learning in non-human vocal learners, providing a mammalian substrate for the evolution of flexible information coding in formants as found in human language. •Vocal learning is crucial for language acquisition but relatively rare in animals•We tested whether gray seals can copy melodies and human formants•Seals were versatile vocal learners copying vowels and peak frequency of melodies•Seals used the same supra-laryngeal structures as humans when copying model sounds Speech information in voiced human sounds is encoded in resonances in the supra-laryngeal tract that emphasize the energy content of selected harmonics. Stansbury and Janik show that gray seals can learn to modify emphasized frequency bands called formants to copy human vowels and melodies, making them an ideal model of human speech development.