Exploring the Interior Structure of White-handed Gibbon and Rat Vocal Communication

by Dassow, Angela Marie, Ph.D., THE UNIVERSITY OF WISCONSIN - MADISON, 2014, 180 pages; 3635735


What is the difference between communication and language? In non-human animals, communication is widely viewed as a behavior; a reflexive activity designed to produce behavioral responses in conspecifics or across species. In contrast, language is a human affair. It transfers conceptual knowledge from speaker to listener and has extraordinarily generalizable descriptive powers. We reevaluate this distinction in the context of vocalizations of white-handed gibbons (Hylobates lar), demonstrating previously unrecognized complexity and structure in their vocalizations.

We begin by employing novel machine learning and statistical methods to identify acoustic primitives in gibbon vocal productions that are unexpectedly governed by rules and statistical distributions common in human speech. Having identified these as the smallest acoustic units in gibbon vocalizations, we present evidence these are also the smallest "atom" that can change the meaning of a gibbon vocalization as determined by ethological observation. This leads to a generalized concept of a phoneme not confined to human language.

Our approach, called Cepstral Self-Similarity Matrices, enables automatic sequencing of gibbon vocalizations into their constituent phonemes. We analyze these sequences using basic Ergodic theory to segment them into distinct subsequences that appear consistently and repeatedly across our gibbon populations in specific referential contexts. For example, predator alarm calls share basic properties, statistical phonemic distributions and overall structure but each displays unique sequences associated with a particular predator. We view these as semantic units within the calls identifying the predator, as opposed to behavioral exhortations intended to trigger responses within the social group.

To further explore the value of our computational approach, the vocal repertoire of laboratory rats is examined. Distinct acoustic units are found and explored for signs of vocal degradation after the rats receive a neurotoxic brain lesion to mimic the signs associated with Parkinson's disease. Doing so revealed distinct, differential vocal loss in acoustic units. Examining the Cepstral Self-Similarity Matrices of each acoustic unit also revealed degradation of acoustic unit structure that previously could not be detected using spectral images. In all, this dissertation has provided new insights into how gibbons and rats communicate as well as provide a new analytical tool to researchers.

AdviserMichael H. Coen
Source TypeDissertation
SubjectsZoology; Behavioral sciences; Computer science
Publication Number3635735

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