Pupil Dilation Reflects Perceptual Priorities During a Receptive Speech Task

Area of Science:

• Auditory perception
• Cognitive psychology
• Psycholinguistics

Background:

• Speech perception involves resolving phonetic ambiguity, which varies between clear and casual speech registers.
• Clear speech is hyperarticulated, reducing phonetic ambiguity, while casual speech has collapsed acoustic spaces.
• Cognitive resources allocated to listening effort are crucial for understanding speech, especially in challenging conditions.

Purpose of the Study:

• To investigate cognitive resources listeners invest during clear versus casual speech perception.
• To examine the impact of background noise on listening effort for different speech registers.
• To utilize pupillometry as an online measure of listening effort.

Main Methods:

• Forty-eight participants completed a probe detection task while listening to clear and casual speech in quiet and noise.
• Pupil size was continuously recorded during speech perception.
• Growth curve analysis modeled pupil size dynamics to capture listening effort over time.

Main Results:

• Pupil dilation was larger in noise, confirming increased listening effort.
• Contrary to hypotheses, pupil dilation was slightly larger for clear speech compared to casual speech.
• Systematic differences in pupil dilation were observed before speech onset, indicating anticipatory effort.

Conclusions:

• Listener motivation, not just phonetic ambiguity, influences listening effort.
• Listeners may allocate more resources to clear speech to maximize acoustic/phonetic fidelity.
• The pupillary system is adaptive, responding to task demands and listener motivation for efficient perception.