The study gives cognitive scientists more tools to study the origins of emotion in the brain. (courtesy of Ohio State University)

Researchers at Ohio State University have uncovered how we convey emotional responses is more complex than previously thought. Previously scientists broke down emotions into six basic categories: happiness, surprise, anger, sadness, fear, and disgust.

However researchers at Ohio State University wanted to dig a little further into the shades of grey between surprised, angry and angrily surprised.

Aleix Martinez, one of the co-authors of the study, said he was amazed at how limiting these basic emotional definitions were for researchers.

"When I started to research on that, it seemed like six was a weird number and was really small," Martinez said. "We started to divide this theory into compound facial expression. You can feel happily surprised or angrily surprised."

They devised a way to measure the facial movements of "compound expressions" by examining the different distinct muscle movements between emotions such as "disgustingly surprised" and "happily surprised." The distinct facial patterns were consistent among his 230 volunteers.

Martinez and his fellow researchers eventually found an additional 15 distinct emotional expressions. He said that these distinct expressions could be used to help people with behavioral problems understand emotion or even be used to help robots of the future have better interactions with people.

"Obviously [for] systems to interact with you more readily, [they] need to understand the emotional systems because we are emotional beings," he said.