TONAL DISTURBANCES IN THAI AFTER BRAIN-DAMAGE

An acoustic-perceptual investigation of the five lexical tones of Thai was conducted to evaluate the nature of tonal disruption in aphasia. Subjects included two Broca aphasics, one transcortical motor, one global, one left subcortical aphasic, one language-delayed adult, and five normals. The five Thai tones (mid, low, falling, high, rising) were produced in isolated monosyllables and presented to native listeners for identification. Measures of F0 were extracted using a cepstral method of analysis. Results from tonal identification tests indicated that the mid and high tones were especially vulnerable to disruption. All significant tonal substitutions resulted in a mid, low, or falling tone. Acoustic analysis revealed that aberrant tones were characterized by falling or rising-falling F0 contours. Findings are discussed from both perceptual and articulatory perspectives on the tone space.