Phonetic coding and its relationship to talker and rate normalization.
Gail R. Tomiak, Kerry P. Green, Patricia K. Kuhl · The Journal of the Acoustical Society of America · 1991
Listeners perceptually adjust for the acoustic variability brought about by differences in talker (voice) and rate information. To account for this adjustment, researchers have posited the existence of normalization processes. The purpose of the experiments reported here was twofold. First, the nature of the relationship between phonetic coding processes and talker and rate normalization processes was examined using monosyllables varying in three dimensions [phonetic (/bi/, /pi/); talker (male, female); rate (fast, slow)] in a speeded classification procedure [W. R. Garner, TheProcessingofInformationandStructure (Erlbaum, Potomac, MD, 1974)]. Subjects classified the syllables along each of the three stimulus dimensions under two testing conditions: when the syllables varied only in the relevant/attended target dimension (single dimension) and when the syllables varied along the relevant and an irrelevant/unattended target dimension (orthogonal). Results indicated that decisions about phonetic identity were dependent upon both talker and rate information: Irrelevant variation in either dimension interfered with (increased reaction time to) phonetic classification. While rate classification was also affected by phonetic variation (integral), talker classification was not (separable). A final experiment, using the same stimuli and reaction time procedure, explored the relationship between the two normalization processes. Results indicated an integral relationship: Variation in talker information interfered with rate classification and vice versa.