A happy smiling face makes less of an impression on the brain than a fearful one, according to research co-led by Psychologist Dr. David Zald, of Vanderbilt University, and reported in the journal Emotion.

The scientists believe that our rapid reaction to frightened faces may be an instinct that evolved as a “threat radar” millions of years ago. Since the whites of the eye become particularly visible when a person is scared, possibly indicating a potential threat. And, such cues may take a short cut through the brain to the amygdala, which processes emotional reactions.

Dr Zald said:

There are reasons to believe that the brain has evolved mechanisms to detect things in the environment that signal threat. One of those signals is a look of fear

We believe that the brain can detect certain cues even before we are aware of them, so that we can direct our attention to potentially threatening situations in our environment.

The scientists set out to determine if people became aware of fearful, neutral or happy expressions at the same speed.

But, measuring response times is normally very difficult, since processing facial information usually takes the brain less than 40 milliseconds. The team therefore used a technique called continuous flash suppression, in which they asked a group of volunteers to look at images of faces through a special viewer; similar to the eyepieces on a microscope, but which was designed to confuse the brain, instead.

Multiple images were rapidly presented to one eye, while a “normal” static image was shown to the other. The multiple images serve as visual “noise”, which slowed down the speed at which the participants became aware of what they were seeing with the other eye.

Quoting Dr Zald again:

If you present different images to the two eyes, usually you will only perceive one of them at a time. The image that registers with the brain typically depends on which eye is dominant for that person. But if one of the eyes is presented by a dynamic, changing stimulus it will basically suppress perception from the other eye.

Using this technique, the researchers asked the volunteers to state when they first became aware of the static image, and they could then measure whether the expression on the face had any impact on how quickly the volunteer became aware of it.

The team found that people became aware of fearful expressions much faster than neutral or happy faces. “We were seeing it pretty much universally,” Dr. Zald said.

The amygdala receives information before it goes to the cortex, which is where most visual information goes first. We think the amygdala has some crude ability to process stimuli and that it can cue some other visual areas to what they need to focus on.

The scientists also made the discovery that their volunteers processed smiling faces more slowly than any other emotion. “What we believe is happening is that the happy faces signal safety,” Dr Zald concluded. “If something is safe, you don’t have to pay attention to it.”

Share & Bookmark this article:

Posted by Jonathan in Psychology, Sociology