Answer: Another language
Clues: “Multi” and “Lingual”
Learning a second language might slow down aging in your brain. Research found that the more languages people speak, the younger their brains appear. Learning an extra language at a younger age and learning to become highly fluent in another language also seem to slow brain aging. People who spoke two languages had brains that appeared around six years younger than those who spoke only one language. For people who spoke three languages, their brains were around seven years younger, and for those who spoke four languages, their brains were around 13 years younger.