How do you react to an emotional face? Depends on how quickly you see it i-ffe8b158868d27db7e28bddd7938b817-ruys1.jpgWhat's your first reaction on seeing this picture of Nora? Are you excited because she appears to be excited? Or do you react to her intent? Perhaps you think she's cute, or maybe even sarcastic. Ultimately you might have all of those reactions.

There's no doubt we're exceptionally fast at responding to faces, and to the emotions they convey. But reacting appropriately, especially when a face signals danger, could be the difference between life and death.

These two ways of reacting to a facial expression correspond to two possible intentions of an expression: to elicit an emotion in someone else, or to express your own emotional state. The result, for the other person, isn't always the same. For example, if you simply mimick the emotion of an angry face, then you too would be angry. But if the angry person was stronger or better-armed than you, you might recognize their anger and become afraid, not angry. So which response comes first?

Kirsten Ruys and Diderick Stapel believe they have devised a way to find out. They asked students to watch movies that quickly flashed emotional faces at them -- so fast that the facial expressions couldn't be consciouly judged. The faces were flashed at two different speeds, illustrated in this video:

Click to watch video (QuickTime required)

The students were instructed to focus on the cross in the center of the screen and react as quickly as possible, indicating when a picture flashed to the left or right of the cross. As you can see in the slowed-down version (which the students never saw), the face flashed very briefly before being masked by a black-and-white rectangle. (Yes, that's me, doing my best to look "angry.") In the "quick" version, the face stayed on-screen for 120 milliseconds. In the "super quick" version, it appeared for just 40 milliseconds. The students were divided into 8 groups, who saw one of four emotions (Anger, Fear, Disgust, or Neutral) at either quick or super quick speeds.

After completing this task, the researchers tested the students' emotions using two different tasks. The first was word-completion. Students were given a few letters from words and were asked to complete them. For example, if they saw "HA" -- the idea is that an angry person might complete it as "HATE," but a cheerful person might complete it as "HAPPY." Here are the results for the students who saw angry faces:


When the images were seen for the longer, "quick" duration, students completed significantly more angry words than disgust or fear words. But when they were only seen for a super-quick 40 milliseconds, angry words weren't completed any more frequently than any of the other words. Overall, there were still more negative words compared to those who had seen neutral faces, but the specific emotion of "anger" wasn't elicited. The same pattern held for people who saw disgusting faces or fearful faces.

The students were also asked to rate their own mood on a scale 1 (positive) to 7 (negative) after finishing the experiment. Here are those results:


When the faces were seen for a longer time period, there was no difference in mood ratings, no matter what expression they had seen during the experiment. But when faces were seen super-quickly, the students who saw negative expressions rated their moods as significantly more negative than students who saw neutral faces.

Ruys and Stapel say this means our facial expressions elicit a mood response in others even before they recognize our particular expression. Over time -- still a very short period of time -- we then are able to decode the particular expression and decide how to respond.

Kirsten I. Ruys, Diederik A. Stapel (2008). Emotion Elicitor or Emotion Messenger? Subliminal Priming Reveals Two Faces of Facial Expressions Psychological Science, 19 (6), 593-600 DOI: 10.1111/j.1467-9280.2008.02128.x

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