The very fact that something as simple as working with puzzles or having once got a good education can improve brain function does prove that multilingualism is not the only path to staying cognitively healthy in your dotage. And plenty of monolinguals do perfectly well at acquiring empathy and social skills early in life. Still, there are roughly 6,500 spoken languages in the world. There must be a reason our brains come factory-loaded to learn more than just one.
What type of vocabulary is most useful to learn; nouns, adjectives, or verbs?
Despite being the world’s lingua franca, English is the most difficult European language to learn to read. Children learning other languages master the basic elements of literacy within a year, but British kids take two-and-a-half years to reach the same point.