Talker normalization is mediated by structured indexical information.

Area of Science:

• Cognitive Science
• Auditory Perception
• Speech Processing

Background:

• Speech perception is significantly impacted by indexical variability, such as differences in talker voices.
• Previous research indicates that processing speech from multiple talkers incurs higher costs (e.g., slower reaction times, reduced accuracy) than from a single talker.
• However, prior studies may not have adequately represented the graded nature of indexical variation found in natural environments.

Purpose of the Study:

• To test the hypothesis that processing costs associated with multiple talkers decrease when stimulus structure is enhanced.
• To investigate how acoustic variability and talker-voice change frequency influence speech processing costs.

Main Methods:

• Listeners performed a speeded classification task involving words with vowels of varying acoustic-phonemic ambiguity.
• Experiment 1 manipulated the acoustic distinctiveness between talkers' voices.
• Experiment 2 manipulated the frequency of talker voice changes within mixed-talker conditions by blocking talkers.

Main Results:

• Response times decreased as acoustic variability among talkers diminished (Experiment 1).
• Blocking talkers in mixed-talker conditions reduced the difference in response times compared to single-talker conditions (Experiment 2).
• These effects were independent of the acoustic-phonemic ambiguity of the target vowels.

Conclusions:

• Indexical structure plays a crucial role in mediating the processing costs associated with hearing different talkers.
• The findings support the Efficient Coding Hypothesis, suggesting that stimulus structure facilitates sensory and perceptual processing.
• Further research is needed to fully define the roles and limitations of stimulus structure in speech perception.