Reduced Eye Blinking During Sentence Listening Reflects Increased Cognitive Load in Challenging Auditory Conditions

While blink analysis was traditionally conducted within vision research, recent studies suggest that blinks might reflect a more general cognitive strategy for resource allocation, including with auditory tasks, but its use within the fields of Audiology or Psychoacoustics remains scarce and its interpretation largely speculative. It is hypothesized that as listening conditions become more difficult, the number of blinks would decrease, especially during stimulus presentation, because it reflects a window of alertness. In experiment 1, 21 participants were presented with 80 sentences at different signal-to-noise ratios (SNRs): 0, + 7, + 14 dB and in quiet, in a sound-proof room with gaze and luminance controlled (75 lux). In experiment 2, 28 participants were presented with 120 sentences at only 0 and +14 dB SNR, but in three luminance conditions (dark at 0 lux, medium at 75 lux, bright at 220 lux). Each pupil trace was manually screened for the number of blinks, along with their respective onset and offset. Results showed that blink occurrence decreased during sentence presentation, with the reduction becoming more pronounced at more adverse SNRs. Experiment 2 replicated this finding, regardless of luminance level. It is concluded that blinks could serve as an additional physiological correlate to listening effort in simple speech recognition tasks, and that it may be a useful indicator of cognitive load regardless of the modality of the processed information.