In the digital age of online dating and selfies, it’s important to always put your best face forward -- or maybe all 21 of them. New research suggests that in addition to the six basic emotions humans present to the world -- happiness, surprise, sadness, anger, fear and disgust -- there are nearly three times as many compound emotions, including expressions such as “happily surprised” and “sadly angry.”

According to researchers from Ohio State University, there are 21 unique emotional expressions, some of which are combinations of two or more emotions. Furthermore, each involves a distinct composition of facial muscles to convey a particular feeling.

“We've gone beyond facial expressions for simple emotions like 'happy' or 'sad,'” Aleix Martinez, a cognitive scientist and associate professor of electrical and computer engineering at the university, said in a statement. “We found a strong consistency in how people move their facial muscles to express 21 categories of emotions.”

Martinez and his team used computers to analyze the facial expressions of 230 volunteers and found that the muscle patterns were surprisingly consistent. Researchers asked participants to prepare responses to several scenarios -- being told they just got some great and unexpected news, hearing they were just accepted to a graduate program or learning that they just got caught a whiff of a bad smell -- and then photographed the subsequent expressions.

Researchers collected 5,000 images in total. Then they mapped several prominent landmarks on the faces, like the corners of the mouth and the edges of the eyebrows, and entered the data into a computer program that identified similarities. For example, parting of the lips clearly expressed disgust, showing teeth was a universal expression of happiness and eyelid tightening conveyed anger, Time notes.

The researchers identified 21 different facial expressions. They even made distinctions between feeling “happy surprise” and “happy disgusted.”

The study, published in the journal Proceedings of the National Academy of Sciences, adds to the growing field of research involved with human emotional expression, something that has perplexed and captivated scientists as far back as ancient Greece.

"In cognitive science, we have this basic assumption that the brain is a computer," Martinez said. "So we want to find the algorithm implemented in our brain that allows us to recognize emotion in facial expressions.”

Previous research was limited by recognizing only six basic categories of emotion, Martinez added. He hopes his team’s research will expand our understanding of how humans process emotion and even help researchers recognize pathological tendencies.

“Hopefully with the addition of more categories, we'll now have a better way of decoding and analyzing the algorithm in the brain,” Martinez said.