Tone languages such as Mandarin use voice pitch to signal lexical contrasts, presenting a challenge for second/foreign language (L2) learners whose native languages do not use pitch in this manner. The present study examined components of an aptitude for mastering L2 lexical tone. Native English speakers with no previous tone language experience completed a Mandarin word learning task, as well as tests of pitch ability, musicality, L2 aptitude, and general cognitive ability. Pitch ability measures improved predictions of learning performance beyond musicality, L2 aptitude, and general cognitive ability and also predicted transfer of learning to new talkers.In sum, although certain non-tonal measures help predict successful tone learning, the central components of tonal aptitude are pitch-specific perceptual measures.

This paper begins by discussing new trends in the use of neurostimulation techniques in cognitive science and learning research, as well as the nascent research on their application in second language learning. To illustrate this, an experiment designed to investigate the impact of transcutaneous vagus nerve stimulation (tVNS), which is delivered via earbuds, on how learners process and learn Mandarin tones is reported. Pupillometry, which is an index of cognitive effort, is explained and illustrated as one way to assess the impact of tVNS. Participants in the study were native English speakers, naïve to tone languages, pseudorandomly assigned to active or control conditions, while balancing for nonlinguistic pitch ability and musical experience. Their performance after tVNS was assessed using a range of more traditional language outcome measures, including accuracy and reaction times from lexical recognition and recall tasks and was triangulated with pupillometry during word-learning to help understand the mechanism through which tVNS operates. Findings are discussed in light of the literatures on lexical tone learning, cognitive effort, and neurostimulation, including specific benefits for learners of tone languages. Recommendations are made for future work on the increasingly popular area of neurostimulation for the field of applied linguistics in the 40th anniversary issue of ARAL.

Difficulty perceiving phonological contrasts in a second language (L2) can impede initial L2 lexical learning. Such is the case for English speakers learning tonal languages, like Mandarin Chinese. Given the hypothesized role of reduced neuroplasticity in adulthood limiting L2 phonological perception, the current study examined whether transcutaneous auricular vagus nerve stimulation (taVNS), a relatively new neuromodulatory technique, can facilitate L2 lexical learning for English speakers learning Mandarin Chinese over 2 days. Using a double-blind design, one group of participants received 10 min of continuous priming taVNS before lexical training and testing each day, a second group received 500 msec of peristimulus (peristim) taVNS preceding each to-be-learned item in the same tasks, and a third group received passive sham stimulation. Results of the lexical recognition test administered at the end of each day revealed evidence of learning for all groups, but a higher likelihood of accuracy across days for the peristim group and a greater improvement in response time between days for the priming group. Analyses of N400 ERP components elicited during the same tasks indicate behavioral advantages for both taVNS groups coincided with stronger lexico-semantic encoding for target words. Comparison of these findings to pupillometry results for the same study reported in Pandža, Phillips, Karuzis, O'Rourke, and Kuchinsky (2020) suggest that positive effects of priming taVNS (but not peristim taVNS) on lexico-semantic encoding are related to sustained attentional effort.

Speech recognition in noisy environments can be challenging and requires listeners to accurately segregate a target speaker from irrelevant background noise. Stochastic figure-ground (SFG) tasks in which temporally coherent inharmonic pure-tones must be identified from a background have been used to probe the non-linguistic auditory stream segregation processes important for speech-in-noise processing. However, little is known about the relationship between performance on SFG tasks and speech-in-noise tasks nor the individual differences that may modulate such relationships. In this study, 37 younger normal-hearing adults performed an SFG task with target figure chords consisting of four, six, eight, or ten temporally coherent tones amongst a background of randomly varying tones. Stimuli were designed to be spectrally and temporally flat. An increased number of temporally coherent tones resulted in higher accuracy and faster reaction times (RTs). For ten target tones, faster RTs were associated with better scores on the Quick Speech-in-Noise task. Individual differences in working memory capacity and self-reported musicianship further modulated these relationships. Overall, results demonstrate that the SFG task could serve as an assessment of auditory stream segregation accuracy and RT that is sensitive to individual differences in cognitive and auditory abilities, even among younger normal-hearing adults.

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