Fast and Flexible: Greater Neural Plasticity in the Language Network During Implicit Linguistic Learning in Children than Adults

It is common wisdom that as children grow into adulthood, language learning would become more effortful and less efficient, yet little empirical evidence directly demonstrates and/or explains this phenomenon. Statistical learning (SL), the unconscious processes to detect and extract regularities from the environment, is a fundamental building block for language development. Understanding how SL changes developmentally can clarify whether children are better equipped than adults to learn linguistic regularities. In two experiments, we directly compared behavioral and neural activation during auditory linguistic (Syllable) SL between children and adults, with nonlinguistic (Tone) SL as a control task. In each task, participants were exposed to streams of structured stimuli that contained four embedded triplets while performing a target-detection task. Real-time SL was measured by the acceleration in reaction times and by the differences in brain activation between structured and random streams of auditory stimuli. Children showed a surprisingly faster learning rate than adults only in Syllable but not in Tone SL. Children also exhibited greater short-term functional plasticity during Syllable SL in the language network, defined using a separate naturalistic story listening task, compared to adults, as evidenced by a stronger and earlier neural sensitivity to sequential structures. Faster linguistic SL was further associated with greater neural sensitivity to linguistic patterns in children’s, but not in adults’, language network. These findings together suggested that children’s developing language network may be more equipped to detect and encode linguistic regularities, allowing for quicker acquisition of new language patterns compared to adults.