How lexical frequency, language dominance and noise affect listening effort–insights from pupillometry

Acoustic, listener, and stimulus-related factors modulate speech-in-noise processes. This study examined how noise, listening experience, manipulated at two levels, native [L1] vs. second language [L2], and lexical frequency impact listening effort. Forty-seven participants, tested in their L1 Hebrew and L2 English, completed a word recognition test in quiet and noisy conditions while pupil size was recorded to assess listening effort. Results showed that listening in L2 was overall more effortful than in L1, with frequency effects modulated by language and noise. In L1, pupil responses to high and low frequency words were similar in both conditions. In L2, low frequency words elicited a larger pupil response, indicating greater effort, but this effect vanished in noise. A time-course analysis of the pupil response suggests that L1–L2 processing differences occur during lexical selection, indicating that L2 listeners may struggle to match acoustic-phonetic signals to long-term memory representations.