Universal principles underlying segmental structures in parrot song and human speech

Dan C Mann,W Tecumseh Fitch,Hsiao-Wei Tu,Marisa Hoeschele

doi:10.1038/s41598-020-80340-y

Abstract

Despite the diversity of human languages, certain linguistic patterns are remarkably consistent across human populations. While syntactic universals receive more attention, there is stronger evidence for universal patterns in the inventory and organization of segments: units that are separated by rapid acoustic transitions which are used to build syllables, words, and phrases. Crucially, if an alien researcher investigated spoken human language how we analyze non-human communication systems, many of the phonological regularities would be overlooked, as the majority of analyses in non-humans treat breath groups, or “syllables” (units divided by silent inhalations), as the smallest unit. Here, we introduce a novel segment-based analysis that reveals patterns in the acoustic output of budgerigars, a vocal learning parrot species, that match universal phonological patterns well-documented in humans. We show that song in four independent budgerigar populations is comprised of consonant- and vowel-like segments. Furthermore, the organization of segments within syllables is not random. As in spoken human language, segments at the start of a vocalization are more likely to be consonant-like and segments at the end are more likely to be longer, quieter, and lower in fundamental frequency. These results provide a new foundation for empirical investigation of language-like abilities in other species.

Highlights

Despite the diversity of human languages, certain linguistic patterns are remarkably consistent across human populations
The ability to generate novel units from low level elements had been cited as a trait that separates humans from other animals: animal repertoires were finite and static while human language needed a generative system to create a vast inventory of symbolic labels[6,7]
The physiological gestures that zebra finches use to produce song do not correspond to the silent intervals surrounding syllables, suggesting that the finches need to combine multiple motor movements to produce one syllable[13]. These motor movements could mark segment boundaries or they could be similar to the articulatory gestures that build segments in spoken human language where there is a complex, learned relationship between physical gestures and the perceptual segment categories

Summary

Introduction

Despite the diversity of human languages, certain linguistic patterns are remarkably consistent across human populations. Understanding segments in non-humans is essential for our understanding the relationship between complex acoustic communication and meaning as well as the evolution of vocal learning and language. Because silence is not the only acoustic cue to segment boundaries in human speech, the algorithm uses rapid transitions in fundamental frequency, amplitude, and/or spectral dispersion (Wiener entropy) to mark segment boundaries.

Results

Conclusion