Fear Is Spread by Body Language, Study Says
for National Geographic News
|November 16, 2004|
A menacing body posture can be as threatening as a frightening facial expression, according to new research.
In the past, scientists have said that human emotions are communicated mainly by facial expressions. But a new study suggests that body posture may be as important as the face in communicating emotions such as fear.
The discovery suggests that the immediate response to other people's fear may be more automatic than previously thought.
The study shows that images of fear affect the emotional part of the brain. Since the link between the emotional brain and action is stronger than the link between the visual brain and action, viewing fearful body expressions may automatically prepare the observer to respond to fear.
"When we talk about how humans communicate, we always talk about things like language," said Beatrice de Gelder, the neuroscientist who led the study. "But just like in the animal world, we also communicate through our bodies without our conscious minds being much aware of it."
De Gelder is a professor at both Harvard Medical School in Massachusetts, and Tilburg University in the Netherlands. The study is published in the Proceedings of the National Academy of Sciences this week.
To date, most investigations of the perception of emotion have concentrated on brain activity generated by the recognition of still images of facial expressions.
For their study, however, de Gelder and her colleagues used video recordings of 18 actors performing emotional actions like opening a door and finding an armed robber standing in front of them. The actors also had to perform neutral actions like pouring water into a glass or combing their hair.
Since previous studies had all used still images, the scientistsfor the purpose of comparisondecided to use still pictures taken from the video clips. But the images showed the whole body with the face of the actor blocked out.
These images were then shown to study participants inside a magnetic resonance imaging (MRI) machine that measured the brain activity of the person watching the pictures.
The researchers found that viewing happy body postures increased activity only in brain regions that processed visual information. However, viewing fearful body postures activated brain regions that process emotional information, as well as those that govern motor processes.
"For the fearful images, there is a lot going on there in the brain," de Gelder said.
The results may help explain how fear spreads.
"If there is any form of contagion that is adaptive, it is the immediate response to the fear of others," said Frans de Waal, a psychology professor at Emory University in Atlanta, Georgia. "If others are fearful, there may be good reason for you to be fearful too."
This fear contagion is easily observed in the animal world.
"If one bird foraging in a flock on the ground suddenly takes off, all other birds will take off immediately after, before they even know what's going on. The one who stays behind may be prey," de Waal said.
The study also shows that the brain's emotional response to fear is probably simpler and more automatic than some researchers have assumed in the past. At a fearful moment, animals and humans need to be response ready, since they are given only a fraction of a second to evaluate the situation.
"Let's say a fire erupts," de Gelder said. "Very quickly [people] will basically adopt the body posture of the person next to them. Evolutionarily, it's a very effective mechanism."
But in higher organisms like humans, that efficiency is sometimes slowed as people start thinking of what they should do.
"They say, Why should I run? Let me look first if there is a reason to run," she said.
De Gelder and her colleagues are now conducting their experiment using full video images, which some scientists say could generate different responses.
"How much more emotional arousal might we see if we were actually in truly fearful situations, as opposed to [being in] the safety of brain scanners?" said Jaak Panksepp, a neuroscientist at Northwestern University in Evanston, Illinois.
Several teams around the world, including de Gelder's, are conducting experiments in which the brain activity of participants is scanned while they're watching movies. This enables scientists to study how emotional actions are based on movement.
In the future such research may help scientists diagnose mental diseases such as Alzheimer's and disorders such as autism and schizophrenia. It may also used in building robotic human companions, which could be improved by building principles of "emotional movement" into them.
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