Neurostimulation and Pupillometry: New Directions for Learning and Research in Applied Linguistics

Abstract

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.

Baseline pupil size encodes task-related information and modulates the task-evoked response in a speech-in-noise task

“…This modelling approach assumes a polynomial behavior of the time series and it is, furthermore, unable to account for potential autocorrelation of the response (Baayen et al, 2017;van Rij et al, 2019). Recently, generalized additive mixed modeling (GAMM; Hastie & Tibshirani, 1990) has been proposed as an alternative method to analyze pupillometry data (e.g., Algermissen et al, 2019;Aydın & Uzun, 2022;Beatty-Martínez et al, 2021;Boswijk et al, 2020;Huijser et al, 2020;Lõo et al, 2016;Pandža et al, 2020). This method overcomes some of the GCA weaknesses and could be used for similar analyses to the one presented in this study.…”

“…The goal of the study was to clarify whether the assumption of independence between baseline pupil size and baseline-corrected TEPR holds for TEPR metrics that characterize the time course of the response beyond PPD and MPD during a speech in noise task. Specifically, this study focused on the analysis of pupil data estimates obtained using growth curve analysis (GCA; Mirman et al, 2008 ), due to their current surge in popularity in the pupillometry literature (e.g., Bianchi et al, 2019 ; Juul Jensen et al, 2018 ; Koch & Janse, 2016 ; Kuchinsky et al, 2013 , 2014 ; McGarrigle et al, 2017 ; Mclaughlin et al, 2020 ; Neagu et al, 2019 ; Winn et al, 2015 ; Winn, 2016 ).…”

300 Hz transcutaneous auricular vagus nerve stimulation (taVNS) impacts pupil size nonlinearly as a function of intensity

“…Pupil response onset latency was also shorter for 300 Hz versus 25 Hz taVNS across sites, and onset latency was shorter for EAM than concha. Pandža et al (2020) examined behavioral and pupillary effects of delivering 50 μs taVNS pulses to the EAM at 300 Hz and 0.2 mA below perceptual threshold during a foreign language learning study.…”

“…Behavioral improvements and electrophysiological changes (reported in Phillips et al, 2021) were observed for participants who received active taVNS, and these changes coincided with distinct changes in TEPR intensity across two training days. However, given the nature of the training task, the TEPR changes in Pandža et al (2020) were interpreted as reflecting between-group differences in the allocation of effort during learning, rather than reflecting the direct effect of taVNS on the LC-NE system.…”

A bioelectronic route to compassion: Rationale and study protocol for combining transcutaneous vagus nerve stimulation (tVNS) with compassionate mental imagery

“…'successful') vagal modulation. Additionally, through the locus coeruleus-noradrenergic pathway, tVNS might influence attentional mechanisms, the activation of which can be assessed using pupillometry [36] and other measures of attention and attentional bias (eye fixations and dwell times) in response to salient stimuli (e.g. positively valenced facial expressions).…”