The color of your face tells others how you feel — even when you don't want them to know.
Be it a frown, a very slight upturn in the corners of one's mouth, or subtly raised eyebrows, we are pretty good at decoding other people's feelings using facial expressions.
However, there's another facial cue that may be even more reliable when it comes to guessing a person's feelings: the color of their face.
In fact, new research suggests that we can accurately identify other people's emotions based purely on the subtle color changes of their faces in up to 75 percent of cases.
The study was carried out by researchers led by Aleix Martinez — a cognitive scientist at the Ohio State University in Columbus — and the findings were published in the journal Proceedings of the National Academy of Sciences.
We can tell emotion from facial color
Martinez and colleagues grouped hundreds of photos of different facial expressions into two color channels, which were equivalent to how human eyes perceive color: a red-green channel, and a blue-yellow one.
Using computer analysis, they realized that different emotions formed different color patterns, and that these patterns were almost identical, irrespective of gender, ethnicity, and skin tone.
Next, the team wanted to see whether people picked up on emotions from facial expressions entwined with color, or whether it was color alone that conveyed feelings.
To test this, they superimposed different color patterns on pictures of neutral facial expressions (for example, a color associated with happiness on a neutral face) and asked 20 study participants to guess the feeling conveyed in the photo.
Based purely on color, the participants guessed correctly 70 percent of the time that a photo conveyed happiness, 75 percent of the time that it conveyed sadness, and 65 percent of the time that it displayed anger.
They then swapped emotion-specific colors onto the "wrong" facial expressions. For instance, they superimposed "angry" colors onto happy faces, and vice versa.
"Participants could clearly identify which images had the congruent versus the incongruent colors," says Martinez. While they didn't know what was wrong, the participants could tell that something was "off."
What red, green, blue, and yellow mean
Martinez and team also designed a computer algorithm that would recognize the emotions. Their algorithm detected human emotion with even more precision than humans: 90 percent accuracy for happiness; 80 perfect for anger; and 75 percent for sadness.
"There's a little bit of every color everywhere," says Martinez. For instance, disgust is usually characterized by a blue-yellow hue around the mouth and a red-green color on the nose and forehead.
"We identified patterns of facial coloring that are unique to every emotion we studied," explains Martinez.
"We believe these color 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 color," he concludes, "but we use them to correctly identify how other people are feeling, whether we do it consciously or not."