## 4 Discussion
### Pupil Dialation in Response to Vocal Samples  
The other aim of this study was to examine the relationship between the pupil dilation in response to listening to AdSD speech samples and the perceived listening effort. To our knowledge, this is the first study to empirically evaluate pupil responses and the amount of effort expended while listening to disordered speech samples in general, and AdSD speech samples in particular. The goal herein was to explore the variability in processing effort as indicated by the peak pupil dilation (PPD). Pupil size is reported to be impacted by cognitive load and more specifically, language processing tasks such as hearing and reading words [12; 17; 22] or sentences [17; 23]. The present aim was to determine whether a sample with increased strain would be associated with an increased PPD with respect to baseline, which would be consistent with increases in the amount of cognitive resources utilized by a listener in a speech reception task [24]. Processing demand is reported to be imposed by either stimulus factors such as linguistic complexity or noise, or as addressed in our study, the quality of the voice sample being assessed. Additionally, it is possible that listener factors such as the capacity of working memory or hearing impairment will influence both perceptual ratings and PPD. Thus, consideration of both speaker and listener factors is essential as they are reported to influence processing demands [25; 26]. The averaged pupil track profiles shown in Figures 3 and 4 are consistent with previous studies investigating the relationship between pupillometry and speech perception in noisy environments [27]. A closer assessment of the pupillary data revealed that stimuli from two talkers (1 and 18), that received the highest perceptual ratings for strain and listening effort, also elicited the highest averaged PPDs. Stimuli from talkers rated lower on strain and effort elicited smaller PPDs. Our results revealed a strong, positive correlation between strain and PPD (0.73), and between effort and PPD (0.66) when averaged across all listeners. Given this positive correlation and the dependence of vocal strain on the presence of AdSD spasms and/or momentary aphonic breaks, the averaged pupillary responses can be deemed to have been evoked in response to the unique quality of the AdSD speech stimuli. The present findings are consistent with those reported by [PERSON] et al. [12; 16; 28] and [PERSON] et al. [12; 17; 29] who examined listening effort through pupillometry and reported larger mean PPD for their normal hearing listeners in low intelligibility than high intelligibility conditions, ascribing larger mental effort to such challenging listening conditions. All participants were tested with all voices in random order, and then tested with all voices again, in a different order. Both subjective and pupillometric responses compared across test and retest. The test-retest correlation coefficients were generally high for the auditory-perceptual ratings. For the test-retest pupil dilation comparision, data from Talker 1 (who was one of the talkers with the highest level of strain and for whom listeners exhibited a high PPD value) was examined more closely in various test-retest presentation orders for a few listeners. These presentation orders included position order seventh (in the test) and position order 22 nd (in the re-test) (Figure 5(a)) and presentation order 21 st (test) and 11 th (re-test) (Figure 5(b)). In all these instances, the first presentation elicited greater PPD than did the second presentation of the same stimulus. The decrease in PPD values may be due to the fact that listeners have already habituated to the stimulus or it may be the consequence of fatigue/boredom. It is known that pupil dilation is influenced by the emotional valence, which represents the attractiveness (positive affect) or aversiveness (negative affect) to an auditory stimulus [30].