We're all familiar with expressions like "red in the face" and "pale with shock".
Could new forms of artificial intelligence someday guess what you're feeling just by looking at the colour of your face?
It's a good bet, according to Ohio State University researchers who study human expressions of emotions.
The study was published recently in the journal Proceedings of the National Academy of Sciences.
Unique patterns of facial colouring
They say subtle changes in facial colour telegraph your feelings to other people – and they created computer algorithms that can detect the same changes.
Even without other clues, their study found people are able to use slight shifts in blood flow colour around the nose, eyebrows, cheeks or chin to correctly identify another person's feelings up to 75% of the time.
"We identified patterns of facial colouring that are unique to every emotion we studied," said lead author Aleix Martinez, a cognitive scientist and professor of electrical and computer engineering.
"We believe these colour patterns are due to subtle changes in blood flow or blood composition triggered by the central nervous system. Not only do we perceive these changes in facial colour, but we use them to correctly identify how other people are feeling, whether we do it consciously or not," Martinez said in a university news release.
Based on those findings, the researchers created computer algorithms that use face colour to correctly recognise human emotion up to 90% of the time. They said these algorithms may lead to new types of artificial intelligence that can recognise and imitate human emotions.
Image credit: The Ohio State University