Auditory temporal acuity in relation to category boundaries; speech and nonspeech stimuli

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Speech Perception

Background:

• The auditory system's ability to resolve temporal changes is crucial for speech perception.
• Previous research suggested categorical perception of speech sounds might stem from psychoacoustic thresholds.

Purpose of the Study:

• To investigate the auditory system's resolving power for temporal changes in speech and nonspeech stimuli.
• To re-evaluate the role of psychoacoustic thresholds versus central processing in sound categorization.

Main Methods:

• Experiments used bilabial voice onset time (VOT) and analogous nonspeech continua.
• Minimized trial-to-trial stimulus uncertainty and cognitive load during testing.
• Assessed discrimination performance under conditions of minimal psychophysical uncertainty.

Main Results:

• Elimination of the local maximum in discrimination performance, previously linked to categorical perception.
• Accurate discrimination for short onset times, with performance decreasing as onset time increases.
• Demonstrated improved overall discrimination performance with reduced uncertainty.

Conclusions:

• Categorization of familiar sounds is likely mediated by central auditory processing, not solely by psychoacoustic thresholds.
• The auditory system's temporal resolving power is finely tuned for early onset times.
• Findings challenge previous explanations of categorical perception based on auditory thresholds.