Synchronized Listening-While-Reading in EFL Vocabulary Learning: Immediate Gains and Exploratory Heart-Rate Patterns

Multimodal input is often assumed to facilitate second-language learning by reducing cognitive demands, but this account may not fully explain digital listening-while-reading. This study examined vocabulary learning and task-related physiological activation in 40 Korean university EFL learners randomly assigned to text-only or synchronized text-with-audio conditions. Vocabulary knowledge was assessed using a 20-item test before and immediately after the task, while heart rate was recorded during task performance and recovery. The text-with-audio group showed substantial vocabulary improvement (M = 67.00 to 80.25, p < 0.001), whereas the text-only group showed no significant improvement (p = 0.096). More importantly, vocabulary gain differed significantly between conditions, with greater immediate gains in the text-with-audio condition. Mean task heart rate (d = 0.59, p = 0.069) and elevation from baseline (d = 0.63, p = 0.053) were numerically higher in the text-with-audio condition, but neither difference reached statistical significance. Thus, the physiological findings are suggestive rather than confirmatory and should not be interpreted as direct evidence of engagement or cognitive load. The findings support a provisional balanced-efficiency framework in which improved multimodal learning may occur without reduced physiological activation, requiring validation with direct cognitive, behavioral, and complementary physiological measures.