Senior Honors Projects, 2010-current

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Award

Spring 2018

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Psychology

Advisor(s)

Michael D. Hall

Tracy E. Zinn

Jeffrey T. Andre

Abstract

Phoneme-level research involving speaking rate has typically relied on a single method of synthetically manipulating rate of speech by compressing the vowel portion of a syllable. This does not mimic what occurs during natural speech production, and therefore could be influencing the perception of voicing contrasts. An experiment was conducted to address this problem by constructing a continuum of voice onset times for the velar place of articulation and then subsequently altering the rate of speech using three methods of manipulation: compressing the vowel, compressing the consonant and vowel proportionate to what occurs naturally, and compressing the total duration of the syllable. Each method of rate manipulation was evaluated at three speeds. The original continuum served as a control condition reflecting normal speed. Medium and fast versions of the continua were also presented, where utterances following the aspiration noise that specified voice onset time were .75 and .50 times the length of the original production at normal speed, respectively. Participants rated each stimulus on a scale of one to six (1 = most /ga/-like - 6 =most /ka/-like). As expected, categorical functions were obtained across continua. There was an observed tendency for stimuli with short VOTs at faster speeds under consonant-vowel and total compression conditions to be rated/categorized as more /ka/-like relative to stimuli at the normal speaking rate. This pattern was not apparent for the vowel manipulation condition, which suggests that vowel compression is an appropriate method to manipulate the speaking rate of voicing contrasts. Total compression did produce consistent responses across speeds around the phonemic boundary and voiceless region of the continua, indicating that total compression could be appropriate for manipulating voiceless consonants with longer voice onset times. Taken collectively, the data seem to show that compressing the consonant portion of a syllable, even to a small degree, can limit the perceptual information that is necessary for categorization.

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