Topics in acoustics, production and perception of psittacine speech
AdvisorPepperberg, Irene M.
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PublisherThe University of Arizona.
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AbstractBy examining psittacine speech (primarily from a Grey parrot, Psittacus erithacus, named Alex) in a series of two acoustic studies, two articulatory studies and one perceptual study, this dissertation demonstrates that some aspects of human language are not unique to our species. The first two studies identify frequency, intensity and durational aspects of, respectively, Alex's vowels (/i,I,e,ε,æ,ɒ,ə,o,U,u/) and stop consonants (/p,b,t,d,k,g/) that either differ from or resemble their human counterparts (primarily I. M. Pepperberg). Our results indicate that Alex produces acoustically distinct phonemes using more high frequency information than do humans. In both studies, we use acoustic data to make predictions about articulation. We also compare Alex's speech to that of a mynah, and conclude that these species use different mechanisms to produce speech. The third and fourth study examine vowel articulation: The third study, an X-ray videotape analysis, establishes that Alex configures his vocal tract in distinct ways for /i/ and /ɒ/. The fourth study models more than 2800 Grey parrot vocal tract shapes as conjoined tubes with known area functions and calculates associated vowel formants. The relationship between these mathematical models and formant values for /i,I,e,ε,æ,ɒ,ə,o,U,u/ is consistent with findings from the vowel study, X-ray study, Grese's unpubl. data and personal observations of relationships between Alex's vocal tract configurations and vowel production. The third and fourth studies show that Alex's "phonemes" are articulatorily distinct. The fifth study is perceptual and examines the relationship between acoustic characteristics of psittacine vowels and the accuracy with which listeners perceive them. We find evidence that Alex's acoustically least "human" vowel, /i/, is very difficult for listeners to perceive unless they have substantial exposure to Alex (on the order of several months). More acoustically prototypical vowels, like /ɒ/, are accurately identified even by less experienced listeners. We thus find that, at least for experienced listeners, Alex's "phonemes" are perceptually distinct. In sum, the dissertation provides acoustic, articulatory and perceptual evidence of phonemes and other phonetic structure in the speech of a psittacid.
Degree ProgramGraduate College