Language proficiency drives listening-related fatigue in those who communicate in English as their second language.

Individuals who listen to speech in their second language ('L2 listeners') are disproportionately impacted by adverse acoustic conditions; a phenomenon coined the 'non-native speech-in-noise disadvantage'. Evidence also suggests that L2 listening taxes cognitive resources to a greater extent than in L1 listeners. Very little, however, is known about the longer-term consequences of this sustained cognitive engagement. Listening-related fatigue refers to the daily life subjective experience of extreme tiredness from effortful listening. The current study recruited a large sample of L2-English listeners (N = 256) to explore factors that predict listening-related fatigue. Approximately half of this sample (n = 126) reported an Indo-European (IE) language (e.g., Italian) as their first language, whereas the other half (n = 130) reported a non-Indo-European (non-IE) language (e.g., Vietnamese) as their first language. Non-IE L2 listeners reported higher overall listening-related fatigue than both IE L2 listeners and a group of monolingual English-speakers (L1-English). Self-rated proficiency and objective vocabulary scores were significant predictors of L2 listening-related fatigue and they moderated the effect of L2 use on listening-related fatigue; individuals who reported increased L2 use were more likely to experience increased fatigue, but only if their self-rated proficiency was low or moderate or their vocabulary score was low. Exploratory mediation analysis suggested that the effect of the L2 listener group (IE vs. non-IE) on listening-related fatigue was attributable to lower self-rated proficiency and objective vocabulary in the non-IE L2 group. To conclude, language proficiency appears to be a strong determinant of listening-related fatigue in L2-English listeners. When L2-English proficiency is low, increased L2-English usage is associated with heightened listening-related fatigue.