Effect of stimulus type and pitch salience on pitch-sequence processing

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal processing

Background:

• Previous research indicated sequence length independence in pitch discrimination for complex tones with resolved harmonics.
• This effect was attributed to automatic frequency-shift detectors (FSDs) activated by harmonic shifts.

Purpose of the Study:

• To test the hypothesis that FSDs mediate the sequence-processing advantage for complex tones.
• To investigate the relationship between pitch salience and sequence processing performance.
• To develop an ideal-observer model for binary sequence discrimination.

Main Methods:

• A same-different discrimination task was used with sequences of pure tones, complex tones, narrow-band noise, and wide-band noise.
• Stimuli varied in pitch or contained pitch sensations elicited by interaural phase shifts.
• An ideal-observer model was developed to compute d' for the discrimination task.

Main Results:

• The sequence-processing advantage for resolved harmonics was not observed with pure tones or noise stimuli designed to activate FSDs.
• Pitch salience did not correlate with processing performance for a fixed level of discriminability.
• The ideal-observer model provided a computational framework for analyzing the task.

Conclusions:

• The findings argue against the FSD hypothesis for the observed sequence-processing advantage.
• Auditory sequence processing is not solely dependent on pitch salience.
• The developed ideal-observer model offers a tool for further research in auditory discrimination.