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Visual acuity, hearing sensitivity, executive functioning, and working memory capacity, were measured to evaluate any differences in these skills between age groups, and to evaluate whether these skills are related to performance on a speech understanding in noise task (i.e., the Question-and-Answer Task).

5.3.2.1 Visual Acuity 5.3.2.1.1 Younger Adults

All younger participants had normal or corrected to normal vision (i.e., ≥1.0 on the FrACT visual acuity measure; Bach, 2007). Younger adults’ visual acuity scores ranged from 1.11 to the maximum score of 2.0 (M = 1.63, SD = .25).

5.3.2.1.2 Older Adults

Six older adults had worse than normal vision (i.e., < 1.0 on the FrACT visual acuity measure) with visual acuity scores ranging from 0.76 to the maximum score of 2.0 (M = 1.18, SD = .32). Pearson product-moment correlation coefficients were computed to test whether visual acuity was related to performance on the Question-and-Answer Task. The results indicated that older adults’ visual acuity scores were not significantly associated with

Response Time or Accuracy for the Static Condition (RT: r = -.04, p = .81; Accuracy: r = .12 , p = .39), Auditory-Visual Condition (RT: r = -.04 , p = .81; Accuracy: r = .11 , p = .45), or the Auditory-Visual with Visual Distraction Condition (RT: r = -.07 , p = .62; Accuracy: r = .10 , p = .47).

5.3.2.2 Hearing Sensitivity

Audiometric thresholds for each age group, as a function of ear and frequency, are summarised in Figure 5.8. All younger participants had normal hearing (i.e., ≤ 25dB HL at .25, .5, 1, 2, 4 kHz). Older adults’ hearing levels were more diverse, ranging from normal to moderately-severe hearing loss (i.e., > 40dB and ≤ 70dB HL at .25, .5, 1, 2, or 4 kHz in the better ear), with the majority of older participants having mild hearing loss (12 participants; > 25 ≤ 40dB HL at .25, .5, 1, 2, or 4 kHz in the better ear) or normal hearing (6 participants). Younger adults had significantly lower thresholds than older adults for both ears at all tested frequencies (all p values ≤ .01).

Figure 5.8. Audiogram Results for the Left and Right Ears. The bold black line represents the mean threshold for older adults as a function of frequency. The fine black lines represent individual audiograms for older adults as a function of frequency. The green shaded area represents the audiometric threshold range for younger adults.

Better Ear Average scores were calculated by averaging hearing thresholds across all tested frequencies for each ear and selecting the lower average threshold. The within group variation for the Better Ear Average was greater for older adults (Min. = 13.00, Max. = 39.00, M = 24.28, SD = 6.45) than younger adults (Min. = 7.00, Max. = 17.00, M = 11.24, SD = 2.34). When Question-and-Answer performance scores were averaged across Answer Types, younger adults’ Better Ear Average scores were not significantly correlated with Response Time or Accuracy for the Static Condition (RT: r = .29 , p = .16; Accuracy: r = -.24, p = .25), Auditory-Visual Condition (RT: r = .18, p = .39; Accuracy: r = .05 , p = .83), or the

Auditory-Visual with Visual Distraction Condition (RT: r = .20, p = .35; Accuracy: r = -.17 , p = .41).

Pearson correlations between older adults’ performance on the Question-and-Answer Task (with performance averaged across Answer Types) and Better Ear Average scores are illustrated in Figure 5.9. There was a significant association between older adults’ Better Ear

Average scores and both Response Time and Accuracy performance for certain conditions. That is, in comparison to older adults with lower Better Ear Average scores, older adults with higher Better Ear Average scores (i.e., poorer hearing sensitivity) were slower to respond for the Auditory-Visual with Visual Distraction Condition (r = .40, p = .05), and were less accurate for the Static Condition (r = -.48, p =.01) and the Auditory-Visual Condition (r = - .57, p < .01). There was not a significant relationship between older adults’ Better Ear Average scores and Response Time for the Static Condition (r = .37, p = .07) or the

Auditory-Visual Condition (r = .31, p = .13). Older adults’ Better Ear Average scores were also not significantly associated with Accuracy for the Auditory-Visual with Visual

Figure 5.9. Pearson Correlations between Older Adults’ Better Ear Average Scores and both Response Time (Top) and Accuracy (Bottom). Circles represent the average score from True and False Answer Types. Solid black lines represent the lines of best fit.

5.3.3 Cognition

Scores from parts A and B of the Trail Making Test were computed to assess age differences in executive control [(Part B-PartA)/PartA]. There was no significant difference between younger (M = 1.00, SD = .50) and older adults’ (M = .90, SD = .55) computed scores (t(98) = 0.98 , p = 0.33). When Question-and-Answer Task performance scores were averaged across Answer Type, Trail Making Test computed scores were not significantly related to younger or older adults’ response times for the Static Condition (Younger: r = .06 , p = .80; Older: r = -.06, p = .79), Auditory-Visual Condition (Younger: r = -.01 , p = .97; Older: r = -.13, p = .56), or Auditory-Visual with Visual Distraction Condition (Younger: r = -.10, p = .66; Older: r = -.13, p = .55), or accuracy for the Static Condition (Younger: r = .14 , p = .50; Older: r = .13 , p = .55), Auditory-Visual Condition (Younger: r = -.07 , p = .74; Older: r = .10, p = .65), or Auditory-Visual with Visual Distraction Condition (Younger: r = -.05, p = .81; Older: r = .19, p = .38).

The listening span (i.e., LSPAN) was used to measure working memory capacity. Younger adults (M = 15.55, SD = 2.20) scored significantly higher on the LSPAN than older adults (M = 9.41, SD = 1.33; t(98) = 6.91 , p < 0.01). Pearson correlation coefficients were calculated to test the relationship between LSPAN performance and performance on each condition of the Question-and-Answer Task when performance scores were averaged across Answer Types. However, no significant associations were found for either age group. That is, younger adults’ LSPAN scores were not significantly correlated with Response Time or Accuracy for the Static Condition (RT-young, r = -.08 , p = .70 RT-old, r = -.38 , p = .06;

Accuracy-young: r = .27, p = .20 Accuracy-old: r = .20, p = .33), the Auditory-Visual Condition (RT-young, r = .02 , p = .93 RT-old, r = -.31 , p = .14; Accuracy-young: r

= .30, p = .14 Accuracy-old: r = .18, p = .40), or the Auditory-Visual with Visual Distraction Condition (RT-young, r = -.06 , p = .78 RT-old, r = -.34 , p = .09; Accuracy-young: r = .34, p = .09 Accuracy-old: r = .11, p = .60).

5.4 Discussion

The current study had two primary aims. The first was to test, on a speech understanding in noise task, whether seeing visual speech that matches the auditory signal improves younger and older adults’ performance (i.e., accuracy and response time) in comparison to an auditory-only condition. The second aim was to test

whether this benefit would be reduced, for either performance measure, when a visual distractor was additionally presented. Consistent with investigations of the visual speech benefit that have used standard sentence recognition tasks, younger and older adults’ speech understanding was more accurate when visual speech that matched the auditory signal was presented in comparison to when no visual speech was presented (i.e., both age groups gained a visual speech benefit; Cienkowski & Carney, 2002; Jesse & Janse, 2012; Middelweerd & Plomp, 1987, Sommers, Tye-Murray, Spehar, 2005; Tye-Murray, Spehar, Myerson, Hale & Sommers, 2016; Winneke & Phillips, 2011).

A novel finding from the current study was that this visual speech benefit was also observed in the response time measure. That is, both younger and older adults responded faster to question-and-answer task trials when matching visual speech was presented in comparison to the auditory-only condition. Response time has typically been used to objectively measure how different SNRs and hearing aid settings affect listening effort (i.e., the level of fatigue experienced by a listener due to the allocation of cognitive resources to a listening task; Gatehouse & Gordon, 1990; Houben, van Doorn-Bierman, & Dreschler, 2013; Meister, Rahlmann, Lemke, Besser, 2018; van

den Tillaart-Haverkate, de Ronde-Brons, Dreschler, & Houben, 2017); however, to the best of our knowledge, the effect of visual speech on response times in a speech understanding in noise task has not been previously measured. Thus, this study is one of the first to show a new type of visual speech benefit in that seeing a talker’s face can significantly reduce response time for speech understanding in noise for both younger and older adults.

Due to age-related declines in attentional control (Lustig, Hasher, & Zacks, 2007; Madden, Connelly & Pierce, 1994), it was expected that there would be a smaller visual speech benefit for older adults (for the response time measure) when the visual distractor was presented. However, the results indicated that both age groups were able to successfully ignore the visual distractor. That is, there was not a significant difference in performance (response time or accuracy) between the

auditory-visual condition and the auditory-visual with distraction condition for either age group.