Sleep duration predicts behavioral and neural differences in adult speech sound learning

Sleep is important for memory consolidation and contributes to the formation of new perceptual categories. This study examined sleep as a source of variability in typical learners' ability to form new speech sound categories. We trained monolingual English speakers to identify a set of non-native speech sounds at 8PM, and assessed their ability to identify and discriminate between these sounds immediately after training, and at 8AM on the following day. We tracked sleep duration overnight, and found that light sleep duration predicted gains in identification performance, while total sleep duration predicted gains in discrimination ability. Participants obtained an average of less than 6h of sleep, pointing to the degree of sleep deprivation as a potential factor. Behavioral measures were associated with ERP indexes of neural sensitivity to the learned contrast. These results demonstrate that the relative success in forming new perceptual categories depends on the duration of post-training sleep.