Timing matters for interactive task-based learning

To investigate the effects of vocabulary practice timing on lexical learning and neural processing during communication tasks, we engaged 80 Japanese learners of English (40 pairs) in information-gap tasks with vocabulary practice in the pre-task or post-task phase. Learning of verb-noun combinations was orally assessed through translation and narrative tasks one week later. To quantify neural coupling between participants during task-based interaction, hyperscanning with fNIRS was used to measure inter-brain synchronization (IBS). Results showed that pre-task vocabulary practice led to greater learning, while post-task practice resulted in higher IBS in the brain region underlying language processing. Better vocabulary practice performance predicted more automatic use of multiword expressions in the post-task condition. IBS in the brain regions underlying social cognition and language processing predicted multiword learning. These findings reveal how practice timing influences neural synchronization and language acquisition, highlighting the importance of balancing lexical learning with communication processes in task-based language teaching.