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.
Pure-tone thresholds are often a poor predictor of hearing difficulties experienced by patients in audiology clinics. Approximately 25 million Americans may experience hearing difficulties despite having audiometric thresholds within normal limits. Pupil diameter increases with increasing listening effort and could provide an objective measure for determining the presence of such subclinical hearing problems. However, the cost and technical requirements of research-grade eye trackers have limited their use in audiology clinics. This study aims to determine the feasibility of using a commercially-available head mounted display (HMD) with integrated eye tracking to collect pupillometry measures during audiological testing. Pupillary data were collected for N = 46 younger normal-hearing adults while they completed clinically-relevant tests including pure tone audiometry, gaps-in-noise (GIN), dichotic digits, and speech-in-noise tests. Across tasks, task-evoked pupillary responses were generally sensitive to differences in listening demands. Results suggest audiologic testing with commercial HMD eye trackers is feasible and provides additional objective information related to listening effort that may help clinicians better understand and address patient needs. [The views expressed in this abstract are those of theauthors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or U.S. Government.]
Some bilinguals may perform worse understanding speech in noise (SIN) in their second language (L2) compared to monolinguals. Poorer performance has been found mostly for late bilinguals (L2 acquired after childhood) listening to sentences containing linguistic context, and less so for simultaneous/early bilinguals (L2 acquired during childhood) and when testing context-free stimuli. However, most studies tested younger participants–little is known about interactions with age. This study addresses this gap by measuring context-free SIN understanding via the Modified Rhyme Test in over 2,000 normal-hearing young and middle-aged bilingual and monolingual adults (ages 18–58; 23% bilinguals, all L2 English). Data collection is ongoing. Interim analyses reveal an interaction of age and group. Word recognition accuracy decreased as age increased for simultaneous and early bilinguals, but was stable for monolinguals and late bilinguals (though worse for bilinguals than monolinguals). Response time was faster for monolinguals but all groups slowed with increasing age at similar rates. These findings suggest an exaggerated age effect for bilingual SIN understanding across early and middle adulthood. [The views expressed in this abstract are those of the author(s) and do not necessarily reflect the official policy of the Department of Defense or the U.S. Government.]
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