2024/10/23
Keio University
Professor Yasuyo Minagawa of the Psychology Laboratory, Faculty of Letters, Keio University; the Keio University Global Research Institute (KGRI) Center for Co-creation of the Future; and the World Premier International Research Center Initiative for Human-Biology-Microbiome-Quantum-Computing (WPI-Bio2Q); along with Lin Cai, a graduate student at the time in the university's Graduate School of Science and Technology; Takeshi Arimitsu, a full-time lecturer, Naomi Shinohara, a concurrent assistant professor, and Takao Takahashi, a professor at the time, from the university's Department of Pediatrics, School of Medicine, in an international collaborative study with the University of Vienna (Professor J. Mueller) and the University of Zurich (Professor S. Townsend, Researcher S. Watson), have revealed through a brain function study using an artificial grammar of sounds that a certain type of grammatical rule learning (hereafter, grammar learning), previously thought to be impossible until around one year of age behaviorally, is possible even in newborns.
The brain regions involved in judging the correctness of learned grammar differ between newborns and 6- to 7-month-old infants. In newborns, it is the left prefrontal cortex, whereas in 6- to 7-month-olds, the study found the involvement of the anterior language area (inferior frontal gyrus) and posterior language area (supramarginal gyrus, superior temporal gyrus) in the left hemisphere, which already correspond to adult functions. Furthermore, analysis of the brain functional circuits involved in grammar learning in newborns revealed numerous functional connections from the left prefrontal cortex to the posterior language area (supramarginal gyrus, superior temporal gyrus)—where responses were seen only in 6- to 7-month-olds—and that new neural circuits involved in learning were activated. This suggests that human infants build a language area network within the first six months of life through the repetition of such learning. The study also gained insights into individual differences in this learning, showing that newborns with inherently stronger long-range functional brain connections at rest—from the bilateral temporal regions, including the posterior language area, to the left prefrontal cortex—tended to learn grammar more efficiently. This revealed that individual differences in newborns' grammar learning ability are related to their inherent functional brain connectivity.
These research findings not only demonstrate the innateness of the human brain's ability to extract and learn grammatical rules but also partially elucidate the developmental mechanism of the neural circuits in the language areas that support the rapid language acquisition of infants after birth. Furthermore, this study, which also clarified individual differences in the brain functions for grammar learning in newborns and their underlying factors, is expected to be applied in the future to elucidating the neural mechanisms of language development delays and developing effective language learning methods. The results of this research were published in "PLOS Biology" on October 22, 2024 (at 2:00 p.m. US Eastern Time).
For the full press release, please see below.