It’s a staple of language classes and parental lectures: Say thank you.

It’s one of the first phrases you learn in a new language, and one whose importance is drummed into children through repeat readings of books like “The Berenstain Bears Say Please and Thank You,” “Richard Scarry’s Please and Thank You Book” and “Thank You, Mr. Panda.”

But as it turns out, human beings say thank you far less often than we might think.

A new study of everyday language use around the world has found that, in informal settings, people almost always complied with requests for an object, service or help. For their efforts, they received expressions of gratitude only rarely — in about one of 20 occasions.

This might seem like a damning verdict on human nature, or evidence of a global pandemic of rudeness. But to the researchers, it’s good news.

“Our basic stance is one of reciprocity,” said Nick Enfield, a linguist at the University of Sydney, who led the study. “When we ask people to help us, the default is that they will.”