Amplitude and phase-shift effects on dichotic listening performance

Abstract

Objective: Previous dichotic listening (DL) studies have shown that interaural amplitude or phase shifts have powerful effects on dichotic ear advantage. However, it is not known how these two factors interact. The present study aims to explore this interaction when amplitude (intensity) and phase (time) shifts occur simultaneously. Design: Participants listened to dichotically presented pairs of consonant-vowel syllables (216 trials) under nine different experimental conditions, systematically varying amplitude (+9 dB) and phase (+35 ms) shifts. Participants reported which syllable they perceived on each trial. Study sample: Thirty-two healthy adults. Results: The results showed an expected right ear advantage (REA) in the baseline (nosound manipulation) condition. While amplitude shifts favoring the right ear were found to have a greater effect on REA than phase shifts, phase shifts favoring the left ear were found to have a greater effect on left ear advantage (LEA) than amplitude shifts. Furthermore, phase shifts favoring the left ear had a greater effect on LEA than phase shifts favoring the right ear on REA. Conclusions: Present results may have consequences for the training of individuals with auditory and phonetic difficulties, e.g. auditory processing deficits or dyslexia, by aiding the design of optimal combinations of acoustic and phonetic training tools.

Key Words::

• Dichotic listening
• phase-shifted hearing
• interaural time difference
• psychoacoustics
• consonant-vowel syllables
• ear advantage

Acknowledgements

We thank Nur Evirgen (clinical psychologist) for her support with the article. We appreciate the efforts of Ugras Erdogan (electrical/electronics engineer) for the hardware and software setup. This work was supported by 2010.KB.SAG.026 and 2011.KB.SAG.002 numbered research projects of the Dokuz Eylul University Rectorate, and Western Norway Health Authorities grant #911423 and 911101, and Research Council of Norway (RCN) #182699, and ERC Grant #249516 to Kenneth Hugdahl.

Note

1. The degrees of freedom (df) in the parentheses indicate the Greenhouse-Geisser corrected df.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.