New research has identified the brain systems involved in language learning and discovered that these systems pre-date the human species. The findings add to the mystery of how language evolved.
The study used past research on language acquisition in children and second language learning in adults to study language origins in the brain.The researchers from Georgetown University, Kent State University, and University of Melbourne specifically looked for studies that analyzed how declarative and procedural memory systems were involved in language learning. These brain systems have been well studied for their involvement in other memory tasks, such as learning new skills or memorizing a list. Ultimately, the meta analysis involved 16 different past studies, which included 665 individuals.
Once the team had the studies, they attempted to find specific patterns between language learning and usage of these memory systems. This search had not been previously done; most prior studies have focused on patterns restricted to a learner's specific target language, or one aspect of language learning, such as grammar or lexicon.
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The results, published online this week in PNAS, revealed that when children learn a first language and adults learn a second language, they use brain circuitry that existed before humans evolved. More specifically, language acquisition for these groups used the declarative system and the procedural memory system.
In the study, children learned to use grammar with their procedural memory system. We use this system when we learn other new skills, such as riding a bike or learning a musical instrument, a statement on the study explained. Adults navigating the unfamiliar grammar rules of a second language tap into the declarative memory system, which helps us memorize shopping lists or recall what we did the day before yesterday.
Stumbling on these two neurologic circuits in a language study surprised the researchers because both existed before human language did. Their role in behaviors other than communication adds to the potential importance of the findings, which contradict a prevailing theory about language acquisition. That theory holds that the brain systems involved in that skill developed specifically for that purpose; this study points to a different order of events.
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"These brain systems are also found in animals—for example, rats use them when they learn to navigate a maze," says study co-author Phillip Hamrick, who teaches language and cognition at Kent State University, in a statement. "Whatever changes these systems might have undergone to support language, the fact that they play an important role in this critical human ability is quite remarkable."
The finding could provide some crucial clues to the mystery of how language evolved. In addition, they could inform future research on the treatment of certain language problems, perhaps even suggesting new medicinal routes for communication issues associated with autism or dyslexia.
