Listening Effort Measured in Adults with Normal Hearing and Cochlear Implants

Abstract

Background: Studies have examined listening effort in individuals with hearing loss to determine the extent of the impairment. Regarding cochlear implants (CIs), results suggest that listening effort is improved using bilateral CIs compared to unilateral CIs. Few studies have investigated listening effort and outcomes related to the hybrid CI.

Purpose: Here, we compared listening effort across three CI groups, and to a normal-hearing control group. The impact of listener traits, that is, age, age at onset of hearing loss, duration of CI use, and working memory capacity, were examined relative to listening effort.

Research design: The participants completed a dual-task paradigm with a primary task identifying sentences in noise and a secondary task measuring reaction time on a Stroop test. Performance was assessed for all participant groups at different signal-to-noise ratios (SNRs), ranging in 2-dB steps from 0 to +10 dB relative to an individual's SNR-50, at which the speech recognition performance is 50% correct. Participants completed three questions on listening effort, the Spatial Hearing Questionnaire, and a reading span test.

Study sample: All 46 participants were adults. The four participant groups included (1) 12 individuals with normal hearing, (2) 10 with unilateral CIs, (3) 12 with bilateral CIs, and (4) 12 with a hybrid short-electrode CI and bilateral residual hearing.

Data collection and analysis: Results from the dual-task experiment were compared using a mixed 4 (hearing group) by 6 (SNR condition) analysis of variance (ANOVA). Questionnaire results were compared using one-way ANOVAs, and correlations between listener traits and the objective and subjective measures were compared using Pearson correlation coefficients.

Results: Significant differences were found in speech perception among the normal-hearing and the unilateral and the bilateral CI groups. There was no difference in primary task performance among the hybrid CI and the normal-hearing groups. Across the six SNR conditions, listening effort improved to a greater degree for the normal-hearing group compared to the CI groups. However, there was no significant difference in listening effort between the CI groups. The subjective measures revealed significant differences between the normal-hearing and CI groups, but no difference among the three CI groups. Across all groups, age was significantly correlated with listening effort. We found no relationship between listening effort and the age at the onset of hearing loss, age at implantation, the duration of CI use, and working memory capacity for these participants.

Conclusions: Listening effort was reduced to a greater degree for the normal-hearing group compared to the CI users. There was no significant difference in listening effort among the CI groups. For the CI users in this study, age was a significant factor with regard to listening effort, whereas other variables such as the duration of CI use and the age at the onset of hearing loss were not significantly related to listening effort.

Figure 1.

Mean hearing thresholds from 125 to 8000 Hz for the participants with hybrid short-electrode CIs. Thresholds were averaged and shown for the implanted ear only. Filled circles indicate mean hearing thresholds, and there is a solid line for the minimum threshold across participants and a dashed line for the maximum threshold across participants. NR indicates no response at that frequency.

Figure 2.

Mean percent correct scores for speech perception in noise (primary task) for all participant groups. The filled circles show results for the normal-hearing group, the open circles for the unilateral CI group, the filled triangles for the bilateral CI group, and the open triangles for the hybrid short-electrode CI group. Results across the SNR conditions are displayed on the x axis and percent correct is displayed on the y axis.

Figure 3.

Listening effort on the Stroop test (secondary task) for all participant groups. Listening effort was calculated by comparing the proportional change in median RT scores from baseline as follows: [(RT on dual task 2 RT baseline)/RT baseline]. The filled circles show results for the normal-hearing group, the open circles for the unilateral CI group, the filled triangles for the bilateral CI group, and the open triangles for the hybrid short-electrode CI group. Results for all six SNR conditions are displayed on the x axis and listening effort is displayed on the y axis.

Figure 4.

Mean percent correct scores on the reading span test for all participant groups. The white bar shows results for the normal-hearing group, the black bar for the unilateral CI group, the gray bar for the bilateral CI group, and the dashed bar for the hybrid short-electrode CI group. Results by group are displayed on the x axis and percent correct is displayed on the y axis.