According to recent research by the University of Ohio (USA), human beings are capable of up to 21 different emotions expressed with the face.
Among the six basic expressions such as happiness, surprise, anger, sadness, fear or disgust , 15 other compound facial expressions have been identified (thanks to the Facial Action Coding System or FACS) (for example: happily surprised or sadly angry) made thanks to a unique combination of muscles.
The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), indicates that human facial expressions can reflect a much wider range of emotions than previously thought . The first person to come up with the list of the six basic emotions of man was Charles Darwin. However, it is time to modernize this list and add at least 21 independent categories of emotions.
The results could be applied to achieve robots with more expressiveness in the face or to improve the understanding of disorders such as depression , post-traumatic stress syndrome , anxiety or autism .





