By Andrea ThompsonLiveScience Staff Writerposted: 20 March 2007
Whether you get stung by a bee or simply watch as a friend gets stung, you might start to run and hide every time a bee buzzes across your path. A new study reveals why you do this: It turns out the brain areas that respond when fear is learned through personal experience are also triggered when we see someone else afraid.
The finding, detailed in the March issue of the journal Social Cognitive and Affective Neuroscience, could explain why some people are afraid of things like spiders and snakes despite little contact with them.
Study participants watched a short video of a person conditioned to fear a so-called neutral stimulus—something people normally wouldn’t fear—paired with something they find naturally aversive, in this case an electrical shock.
The person in the video watched colored squares on a computer screen: When a blue square appeared, the person received a mild shock; when a yellow square appeared, there was no shock. The participant in the video responded with distress when the blue square appeared—he would blink hard, tense his cheek muscles, and move his hand.
“So it’s clear that he’s uncomfortable, he’s in distress,” said study team member Andreas Olsson of Columbia University. “And he’s already in distress before he receives the shock, you see him anticipate receiving the shock.”
By contrast, the participant in the video appeared relaxed when the yellow square popped up.
Participants were told they would take part in a similar experiment, and when presented with the blue square, they responded with fear, anticipating a shock, though they were never actually shocked.
“Just by watching, they learn themselves,” Olsson explained.
The fear response of the subjects was measured by how much they sweated (lie detector tests operate in a similar way).
This secondhand learning was reflected in the brain. In previous classical conditioning experiments where a fear is learned first-hand, a part of the brain called the amygdala has been shown to be critical to the development and expression of fears.
The scientists monitored the brain activity of each participant during the experiment. Imaging showed that the amygdala responded both when the subjects watched the video of someone else receiving shocks and when they were presented with the blue squares themselves.
“We found that the amygdala is involved both when you’re watching somebody receiving shocks, and when you’re expecting to receive shocks later on yourself,” Olsson said.
So it seems that similar processes in the brain are triggered both when fears are experienced first-hand and when they are observed in others.
In the real world
The findings could help explain why people are afraid of things in scary movies or why a child learns to fear snakes, spiders or even people of other races after seeing their parents’ fearful responses.
“You learn by observing other people’s emotional expressions, and what we are showing is that that can be as effective as having those direct experiences yourself,” Olsson said. “That’s probably one of the reasons why a lot people are having phobias of certain kinds of stimuli, such as snakes and spiders.”