Engaging effort improves efficiency during spoken word recognition in cochlear implant users

Word recognition is generally thought to be supported by an automatic process of lexical competition, at least in normal hearing young adults. When listening becomes challenging, either due to properties of the environment (noise) or the individual (hearing loss), the dynamics of lexical competition change and word recognition can feel effortful and fatiguing. In cochlear implant users, several dimensions of lexical competition have been identified that capture the timing of the onset of lexical competition (Wait-and-See), the degree to which competition is fully resolved (Sustained Activation), and how quickly lexical candidates are activated (Activation Rate). It is unclear, however, how these dimensions relate to listening effort. To address this question, a group of cochlear implant users (N=79) completed a pupillometry task to index effort and a visual world paradigm task to index the dynamics of lexical competition as part of a larger battery of clinical and experimental tasks. Listeners who engaged more effort, as indexed by peak pupil size difference score, fell lower along the Wait-and-See dimension, suggesting that these listeners are engaging effort to be less Wait-and-See (or to begin the process of lexical competition earlier). Listeners who engaged effort earlier had better word and sentence recognition outcomes. The timing of effort was predicted by age and spectral fidelity, but no audiological or demographic factors predicted peak pupil size difference. The dissociation between the magnitude of engaged effort and the timing of effort suggests they perform different goals for spoken word recognition.