Repairing misperceptions of words early in a sentence is more effortful than repairing later words, especially for listeners with cochlear implants

The process of repairing misperceptions has been identified as a contributor to effortful listening in people who use cochlear implants (CIs). The current study was designed to examine the relative cost of repairing misperceptions at earlier or later parts of a sentence that contained contextual information that could be used to infer words both predictively or retroactively. Misperceptions were enforced at specific times by replacing single words with noise. Changes in pupil dilation were analyzed to track differences in the timing and duration of effort, comparing listeners with typical hearing or with CIs. Increases in pupil dilation were time-locked to the moment of the missing word, with longer-lasting increases when the missing word was earlier in the sentence. CI listeners showed elevated pupil dilation for longer periods of time after listening, suggesting lingering effects of effort compared to listeners with TH. When needing to mentally repair missing words, CI listeners also made more mistakes on words elsewhere in the sentence, even though these words were not masked. Stimulus-related effects were not evident in basic measures like peak pupil dilation, and only emerged when the full-time course was analyzed, suggesting the timing analysis adds new information to our understanding of listening effort. Taken together, these results demonstrate that some mistakes are more costly than others and incur different levels of mental effort to resolve the mistake, underscoring the information lost when characterizing speech perception with simple measures like percent-correct scores.