Phylogeny and mechanisms of shared hierarchical patterns in birdsong

• Published in: Current biology Vol. 31; no. 13; pp. 2796 - 2808.e9
• Main Authors: James, Logan S., Mori, Chihiro, Wada, Kazuhiro, Sakata, Jon T.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 12-07-2021
• Subjects: communication; compression; cultural evolution; linguistics; Menzerath’s law; motor biases; music; songbird; speech; universals; universals; linguistics; music; Menzerath’s law; speech; songbird; motor biases; compression; communication; cultural evolution
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2021.04.015

Organizational patterns can be shared across biological systems, and revealing the factors shaping common patterns can provide insight into fundamental biological mechanisms. The behavioral pattern that elements with more constituents tend to consist of shorter constituents (Menzerath’s law [ML]) was described first in speech and language (e.g., words with more syllables consist of shorter syllables) and subsequently in music and animal communication. Menzerath’s law is hypothesized to reflect efficiency in information transfer, but biases and constraints in motor production can also lead to this pattern. We investigated the evolutionary breadth of ML and the contribution of production mechanisms to ML in the songs of 15 songbird species. Negative relationships between the number and duration of constituents (e.g., syllables in phrases) were observed in all 15 species. However, negative relationships were also observed in null models in which constituents were randomly allocated into observed element durations, and the observed negative relationship for numerous species did not differ from the null model; consequently, ML in these species could simply reflect production constraints and not communicative efficiency. By contrast, ML was significantly different from the null model for more than half the cases, suggesting additional organizational rules are imposed onto birdsongs. Production mechanisms are also underscored by the finding that canaries and zebra finches reared without auditory experiences that guide vocal development produced songs with nearly identical ML patterning as typically reared birds. These analyses highlight the breadth with which production mechanisms contribute to this prevalent organizational pattern in behavior.
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•Birdsong follows Menzerath’s law: the greater the whole, the smaller the parts•This relationship can be observed in null models with constrained element durations•The deviation from chance varies across phylogeny and level of song organization•Motor production biases are important for the emergence of this pattern
Many behavioral patterns follow Menzerath’s law (ML): the more constituents in an element, the shorter the constituents. James et al. describe the existence of and variation in this pattern across 15 songbird species. Such patterns can emerge by and deviate from chance, and vocal production biases contribute to the emergence of ML-like patterns.