Anodal transcranial direct current stimulation over the left dorsolateral prefrontal cortex improves L2 listening but not reading comprehension

Abstract Second language (L2) processing places substantial demands on working memory (WM). Because WM training programs are time-consuming and effortful, the present study examined whether transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC), a region associated with WM, can facilitate L2 comprehension. Intermediate L2 learners of Spanish were randomly assigned to an active or sham group. Both groups completed pre- and posttests of listening and reading comprehension; between tests, the treatment group received two 20-minute sessions of 2.0 mA anodal tDCS over the left DLPFC, whereas the sham group received only brief stimulation. Results showed no improvement in reading comprehension, but the treatment group exhibited significant gains in listening comprehension from pre- to posttest and relative to the sham group. These findings suggest that anodal tDCS over the left DLPFC facilitates L2 listening comprehension under the present experimental conditions, offering a potential neuromodulatory aid for adult learners.