Bilinguals are smarter, says science. But the idea is relatively new. Up until the 1970s, most educators had believed that learning two languages at the same time would confuse children and slow their cognitive growth.

Science disagreed with these opinions, says Ellen Bialystok, a professor of psychology. The arrival of new technology in the 1970s allowed scientists a new way to investigate how different brains process language.

Bialystok has been researching the bilingual brain for decades. She firmly believes bilinguals aren’t smarter than the single-language learners, but bilingual brains differ in their use of executive function-a system that both helps the brain access particular regions or memories and allows a person to switch between tasks.

Contrary to media reports, executive function is not the same as intelligence, Bialystok adds. Even if the relationship between bilingualism and actual intelligence is unclear, executive function can help people do a lot of things that may make them seem smarter, such as doing more things at the same time and cancelling out things that take their attention away.

Many people believe that knowing at least one other language makes it easier to learn a new one, and cognitive function may play a part in that-the equivalent of good study habits for your brain. But Bialystok thinks cognitive function has less impact on language learners than the similarities between languages’ structure and vocabulary. “In learning those patterns, you can get a bit of a free ride in learning a new language,” she says. Despite the overall cognitive benefits, bilingualism may present some disadvantages. When children learn vocabulary, monolinguals can spend more time remembering words in one language, while bilinguals have to construct two different vocabularies.

“The biggest advantage in being bilingual is the same as having great international friends: It allows a person to understand a different way of thinking, with unique philosophies and assumptions about how others see the world,” Bialystok adds.

We hear “Have a nice day!” every day and everywhere. It may be a pleasant gesture or a meaningless expression. When my friend Maxie says “Have a nice day” with a smile, I know she sincerely cares about what happens to me. I feel loved and secure since another person cares about me and wishes me well.

“Have a nice day. Next!” This version of the expression is spoken by a salesgirl in the supermarket who is rushing me and my groceries out of the door. The words come out in the same tone with a fixed procedure. They are spoken at me, not to me. Obviously, the concern for my day and everyone else’s is the management’s attempt to increase business.

The expression is one of those behaviors that help people get along with each other. Sometimes it indicates the end of a meeting. As soon as you hear it, you know the meeting is at an end. Sometimes the expression saves us when we don’t know what to say. “Oh, you just had a tooth out? I’m terribly sorry, but have a nice day.”

The expression can be pleasant. If a stranger says “Have a nice day” to you, you may find it heart-warming because someone you don’t know has tried to be nice to you.

Although the use of the expression is an insincere, meaningless social custom at times, there is nothing wrong with the sentence except that it is a little uninteresting. The salesgirl, the waitress, and all the countless others who speak it without thinking may not really care about my day. But in a strange and comfortable way, it’s nice to know they care enough to pretend they care when they really don’t care all that much. While the expression may not often be sincere, it is always spoken. The point is that people say it all the time when they like.

Language is always changing. In a society where life continues year after year with few changes, the language does not change, either. The earliest known languages had difficult grammar but a small, limited vocabulary. Over the century, the grammar changed, and the vocabulary grew. For example, the English and Spanish people who came to America during the sixteenth century gave names to all new plants and animals they found. In this way, hundreds of new words were introduced into English and Spanish vocabularies. Today life is changing very fast, and language is changing fast too.

There are several major language families in the world. Some scientists say there are nine main families, but other scientists divide them differently. The languages in each family are connected, and scientists think that they came from the same parent language. About 3 percent of the people in the world speak languages that are not in these major families.