In a study that now seems embarrassingly overdue, scientists have tripled the list of human facial expressions from six to 21 — adding such emotions as "sadly surprised" and "happily disgusted."
Previous studies on emotional facial expressions have focused on six basic categories — happiness, surprise, anger, sadness, fear, and disgust. There's obviously more to human expressions than just these (only one positive emotion? really?), leading a team of researchers from Ohio State University to take a closer look.
To do so, the researchers analyzed the facial expressions of over 230 volunteers (100 males and 130 females) as they responded to various verbal cues (e.g., "you just got some great, unexpected news" and "you smell a bad odor"). A body language database was then searched for similarities and differences in the 5,000 images produced. Then, with the help of computers, the researchers matched facial movements — like the corners of the mouth or outer edge of the eyebrow — to emotions. Their work revealed a significant amount of consistency.
The resulting paper, which now appears in the Proceedings of the National Academy of Sciences, describes an important group of expressions called compound emotion categories — emotions that can be constructed by combining basic component categories to new ones.
Of the 21 emotions now documented, some of the new ones include "happily surprised," combining the facial movements required for "happy" and "surprised." Other expressions include "angrily disgusted," "sadly fearful," and "happily disgusted," which involves the scrunching of the eyes and nose while smiling.
Read the entire study at PNAS: "Compound facial expressions of emotion."