When he went online, Timothy said, “I found videos of people who had been studying for a year, inching along, and I thought, yeah, I can do that. I never imagined I’d be the center of so much attention.”

ON a Saturday in late February, Timothy had a visit from a classmate named Tamvi Agrawal, who agreed to help him with his Hindi. He had been studying the language seriously for about a month, beginning with the alphabet and grammar, and moving on to flash cards and Bollywood songs. In another week, he planned to make a video. His pronunciation was terrible, he said.

“It’s really not bad,” Tamvi said.

“Do you know what ergativity is?” he asked her, referring to a property of some languages, including Hindi, by which a verb’s subject changes case when the verb is intransitive. She did not.

Timothy often comes out with constructions like this, brainy but not arrogant, a product of many hours spent alone in study. With little prodding, he talks enthusiastically about the history of Islamic expansion or the areas of the brain associated with language. One day, discussing Turkish, he asked a visitor if he knew what an agglutinative language was. (It is a language in which new words are created by adding prefixes and suffixes.) Though languages are at their base social connectors, their study, for the most acquisitive, can be isolating. When school is out, Timothy said, he spends up to 15 hours a day studying, teaching himself the rudiments of a language in two or three weeks.

Hyperpolyglots have been the objects of curiosity at least since the 19th century, when Cardinal Giuseppe Mezzofanti of Bologna was said to have mastered more than 50 languages. For nearly as long, people have debated whether their ability was innate or learned.

The answer, neurolinguists are now discovering, is a bit of both, said Loraine Obler, a linguist and a professor at the City University of New York who has studied bilingualism’s effect on the brain. “There are people whose brains are set up to do language learning,” she said, “the same way some people are more talented at drawing.” Also, she added, “The brain’s ability to absorb increases as we know more languages. Having a second language at a young age helps you learn a third, even if they’re unrelated.”