Specific brain areas increase in size and function, including Broca’s area, which is usually in the left hemisphere and involved in language production. When children grow up bilingual, both languages are processed in the same area. Yet, when adults learn a second language, a separate area develops close to the first.
Some adults learn more quickly than others and one study showed differences in the brain areas that changes: The hippocampus and Broca’s area altered most in the fast learners and the motor cortex in slower students. Some effects depend on the person’s first language. For example, native Japanese speakers cannot readily distinguish the letter “r” and “l” or “t” when learning English because, in their brains, both of these sounds activate the same area. In native English speakers, however, the sounds activated distinct areas.
More generally, learning a new language improves brain function, providing better memory, more mental flexibility and creativity, and can even delay the onset of the dementia.