(Don’t) Sleep On Tone: Effects of Overnight Sleep-Dependent Consolidation on Multimodal L2 Lexical Tone Learning

Acquiring L2 Mandarin lexical tones is difficult for L1 English speakers. Gestures and sleep consolidation independently support L2 phonological learning, but their interactive effects remain underexplored. We examined the effect of sleep on L2 Mandarin lexical tone acquisition by L1 English speakers and how observing pitch gestures modulates this effect. Sixty-four L1 American English speakers without prior tonal language experience learned monosyllabic L2 Mandarin words with or without pitch gestures and were tested at pre-test, immediate post-test, and a 24-hour delayed post-test. Better sleep quality predicted improved accuracy and faster responses in the delayed post-test in the no gesture condition. Observing pitch gestures mitigated these sleep-dependent gains, suggesting that pitch gestures may enhance initial encoding so that overnight consolidation is less critical. These results extend research examining the impact of sleep on L2 tone acquisition to atonal L1 speakers and reveal interactions between multimodal learning and sleep-based memory consolidation.