Graduation Year

2006

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Communication Sciences and Disorders

Major Professor

Stefan A. Frisch, Ph.D.

Co-Major Professor

Catherine L. Rogers, Ph.D.

Committee Member

Jean C. Krause, Ph.D.

Keywords

ultrasound, articulatory gestures, slips of the tongue, consonants, tongue twister

Abstract

Speech errors have been utilized since the beginning of the last century to learn

more about how speech is produced, both physically and cognitively. Collection of

speech errors has progressed from writing down naturally occurring speech errors to

recording experimentally induced speech errors to current studies, which are using

instrumentation to record acoustic and kinematic information about experimentally

induced speech errors. One type of instrumentation being used in articulatory research is

ultrasound. Ultrasound is gaining popularity for use by those interested in learning how

speech is physically produced because of its portability and noninvasiveness. Ultrasound

of the tongue during speech provides visual access to the articulatory movements of the

tongue.

This study utilizes ultrasound recordings of speech errors in two ways. In

Experiment 1, ultrasound images of participants’ tongues were recorded while they read

tongue twisters designed to elicit speech errors. The tongue twisters were CVC words or

CV syllables with onset velar or alveolar stops. Within the ultrasound video, the angle of

the tongue blade and elevation of the tongue dorsum were measured during the onset stop

closure. Measurements of tongue twisters were compared to baseline production

measures to examine the ways in which erroneous productions differ from normal

productions. It was found that an error could create normal productions of the other

category (i.e., categorical errors) or abnormal productions that fell outside the normal

categories (i.e., gradient errors).

Consonant productions extracted from ultrasound video were presented auditory

only to naïve listeners in Experiment 2. Listeners heard a variety of normal, gradient

error, and categorical error productions. Participants were asked to judge what they

heard as the onset sound. Overwhelmingly, the participants heard normal productions as

well as gradient error productions as the target sound. Categorical error productions were

judged to be different from the target (e.g., velar for alveolar). The only effect of

erroneous production appears to be a slight increase in reaction time to respond with a

choice of percept, which may suggest that error tokens are abnormal in some way not

measured in this study.

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