Humans express a broader range of emotions via unique facial expressions than previously thought including ‘happily disgusted’ and ‘sadly angry’.
Researchers used computers to code the expressions of 230 people and identified 21 expressions which use a unique combination of muscles distinct from all the others.
Human cognition studies often employ photographs of facial expressions of emotions: happiness, surprise, anger, sadness, fear and disgust.
But research, until now, has been confined to just those six basic emotions.
However, Aleix Martinez of Ohio State University and colleagues expanded expressions by combining elements of the six basic expressions to create compound expressions such as ‘happily surprised’ or ‘fearfully disgusted’.
Martinez describes ‘happily disgusted’ as “how you feel when you watch one of those funny ‘gross-out’ movies and something happens that’s really disgusting, but you just have to laugh because it’s so incredibly funny.”
The authors photographed the faces of 230 people, each displaying the six basic expressions of emotion and 15 compound expressions.
To determine whether the expressions are unique enough to be distinguished from others, the authors used a Facial Action Coding System (FACS) which identifies which facial muscle groups are used to create an expression.
The analysis revealed that the 21 expressions used a unique combination of muscles different from all other expressions.
A computer model of face perception identified the six basic expressions with 96.9% accuracy and the 15 compound expressions with 76.9% accuracy.
The results suggest that the expanded library of facial expressions of emotions may be useful in human cognition and brain studies, as well as for the design of human-computer interfaces and computer vision systems.
Which face are you?
The article, Compound facial expressions of emotion, by Shichuan Du, Yong Tao, and Aleix M. Martinez, is pubished in PNAS (Proceedings of the National Academy of Sciences).
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