Impaired Performance in Noise: Disentangling Listening Effort from the Irrelevant Speech Effect

Noise can reduce the intelligibility of spoken language and increase the effort necessary to understand speech. Listening effort, "the deliberate allocation of mental resources to overcome obstacles in goal pursuit when carrying out a [listening] task" (Pichora-Fuller et al., 2016), is commonly assessed by measuring response times to secondary tasks while listening to speech or by testing memory for the content of the speech. Increasing the level of background noise tends to slow responses and impair memory, and these effects are attributed to the resource-intensive process of reevaluating speech that was initially obscured or misheard. However, given that noise can impair performance on cognitive tasks that do not require processing auditory information, it is possible that noise-induced impairments typically ascribed to processing degraded speech may instead reflect increased cognitive load from the presence of noise itself. The current study assessed whether noise, in the absence of a speech task, can affect performance on tasks intended to measure listening effort. In Experiment 1 (positive control), target speech consisting of single words was presented aurally in background noise and we measured listening effort with three commonly-used paradigms. Experiment 2 was identical except that the target words were presented orthographically rather than aurally. Results showed that noise impaired performance on all three tasks when the target stimuli were presented aurally, consistent with a large body of work in the listening effort literature. Experiment 2 revealed that performance on some tasks was impaired by the presence of masking noise (particularly two-talker babble), indicating some domain-general interference. However, the magnitude of the noise-induced interference effects were markedly smaller in Experiment 2 than Experiment 1, suggesting that measures of listening effort capture variability attributable to the challenges associated with listening to speech in noise, and do not simply measure distraction or noise-induced cognitive interference.