Communication under sharply degraded auditory input and the “2-sentence” problem

Abstract

Introduction: Many cochlear implant (CI) users who do quite well in standard clinical tests of speech perception report that a great amount of effort is required when listening in real-world situations. We hypothesize that the combined constraints of the sharply degraded signal provided by a CI and finite cognitive resources may lead to a "tipping point" when listeners are confronted with speech material that is more complex than the single words or single sentences that are used in clinical tests. Beyond this tipping point, communication may become too difficult, even for CI users whose standard speech intelligibility scores are above average. Methods: Here, we investigate whether speech identification performance and processing effort (indexed by pupil dilation measures) are affected when CI users or normal hearing control subjects are asked to repeat two sentences presented sequentially instead of just one sentence. Results: Response accuracy was minimally affected in normal hearing listeners, but CI users showed a wide range of outcomes, from no change to decrements of up to 45 percentage points. The amount of decrement was not predictable from the CI users' performance in standard clinical tests. Pupillometry measures tracked closely with effort in both the CI group and the normal hearing group, even though the latter had speech perception scores near ceiling levels for all conditions. Discussion: A communicative tipping point may be reached in many (but not all) CI users in response to input that is only minimally more challenging than standard clinical tests; specifically, when two sentences are presented sequentially before requesting a response, instead of presenting just a single sentence at a time. This potential "two-sentence problem" represents one of the simplest possible scenarios that go beyond presentation of a single word or sentence, and it raises the possibility that even good performers in clinical tests of speech perception may be brought beyond the tipping point by other ecologically relevant manipulations. The present findings also raise the possibility that a clinical version of a 2-sentence test may provide actionable information for counseling and rehabilitating CI users.

The effort of repairing a misperceived word can impair perception of following words, especially for listeners with cochlear implants

“…Notably, this result emerged only for those CI listeners whose speech recognition score was minimally affected by the presence of the second sentence in the series; CI listeners who showed a two-sentence decrement failed to show this effort allocation pattern. Gathering observations bySvirsky et al (2024),Winn and Moore (2018) and the current study, it appears that listeners who excel at speech recognition (either younger TH listeners or better-performing CI listeners) show temporal allocation of listening effort that reflects the demands of the task and in-the-moment anticipation. Absence of this effect might be explained by a phenomenon observed byZekveld et al (2019) who found that the reliable effects of SNR/sentence intelligibility for pupil responses was entirely overridden by the presence of an extra memory load task during the experiment.Supporting the notion that effort allocation reflects strategic use of cognitive resources, recent results byJohns et al (2024) suggest that listening effort depends at least partly on the extent to which individuals have mobilized their attention in anticipation of the difficulty of the upcoming task Vaden et al (2022).…”

“…Variation in the conditional front-loading or pacing of effort was also observed by Svirsky et al (2024). In their experiment, the pupil response during the presentation of a sentence grew at a slower rate when listeners were cued to anticipate two sequential sentences.…”

“…Carryover effects from one utterance to the next have rarely been examined directly. In one recent study, Svirsky et al (2024) presented listeners with two sentences sequentially instead of just one, finding that the detrimental impact on two-sentence repetition performance ranged up to 45 percentage points. In that study, more than half of CI listeners' scores dropped by 10 or more percentage points, and over a third declined by more than 20 points when adding the second sentence.…”