What you say communicates only about half of what people hear.

According to UCLA professor Albert Mehrabian, 55% of the message you convey comes from your body language.

That’s why studying body language has such a long history.

None other than Charles Darwin wrote the first academic investigation into body language, his “The Expression of the Emotions in Man and Animals,” published back in 1872.

Over the past century science has made lots of advances into understanding the many social meanings of body language. Here are 17 of the most useful findings, pulled from Psychology Today, research journals, and a few awesome books.

Max Nisen contributed research to an earlier version of this article.