title: The Impact of Auditory Spectral Resolution on Listening Effort Revealed by Pupil Dilation.
abstract: OBJECTIVE
  This study measured the impact of auditory spectral resolution on listening effort. Systematic degradation in spectral resolution was hypothesized to elicit corresponding systematic increases in pupil dilation, consistent with the notion of pupil dilation as a marker of cognitive load.
  
  
  METHODS
  Spectral resolution of sentences was varied with two different vocoders: (1) a noise-channel vocoder with a variable number of spectral channels; and (2) a vocoder designed to simulate front-end processing of a cochlear implant, including peak-picking channel selection with variable synthesis filter slopes to simulate spread of neural excitation. Pupil dilation was measured after subject-specific luminance adjustment and trial-specific baseline measures. Mixed-effects growth curve analysis was used to model pupillary responses over time.
  
  
  RESULTS
  For both types of vocoder, pupil dilation grew with each successive degradation in spectral resolution. Within each condition, pupillary responses were not related to intelligibility scores, and the effect of spectral resolution on pupil dilation persisted even when only analyzing trials in which responses were 100% correct.
  
  
  CONCLUSIONS
  Intelligibility scores alone were not sufficient to quantify the effort required to understand speech with poor resolution. Degraded spectral resolution results in increased effort required to understand speech, even when intelligibility is at 100%. Pupillary responses were a sensitive and highly granular measurement to reveal changes in listening effort. Pupillary responses might potentially reveal the benefits of aural prostheses that are not captured by speech intelligibility performance alone as well as the disadvantages that are overcome by increased listening effort.
authors: 1Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA; 2Department of Surgery, University of Wisconsin-Madison, Madison, Wisconsin, USA; and 3Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors: Matthew B
authors: MB
authors: Winn
authors: Jan R
authors: JR
authors: Edwards
authors: Ruth Y
authors: RY
authors: Litovsky
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009622:Noise; D011680:Pupil / Q000502:physiology*; D013063:Speech Discrimination Tests; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult
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