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New Insight on Stress


Researchers at Tel Aviv University are providing new insight on stress and the finding could have implications for care provided to victims of terrorism or natural disasters. Researchers believe the laboratory research challenges what we know about stress.

Using the natural predator-and-prey relationship between the barn owl and the vole, a small animal in the rodent family, researchers were able to test unified group responses to a common threat.

Prof. David Eilam and his research team showed that while anxiety levels can differ among individuals in normal circumstances, surprisingly, group members display the same level of anxiety when exposed to a common threat.

He feels this could explain human behavior in response to trauma or terror, such as the citizens of New York City in the days after the 9/11 terror attacks, or after natural disasters such as the recent earthquakes in Haiti and Chile.

"These are times when people stand together and accept a general code of conduct," explains Prof. Eilam.

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He measured the anxiety of three groups of voles. They placed the voles in a peaceful environment and measured how much time each vole spent out in the open and then in protected areas. The more time a vole spent in protected areas, the higher the anxiety level, though this varied among individual voles.

Then the researchers exposed the voles to a common threat, placing the voles’ cage within a barn owl enclosure, and attracted owls to the cages by placing meat on top of the cage. The voles’ experience was one of being attacked. After a night of exposure to their natural predator, the voles were tested once again for anxiety. Researchers found that each vole was equally stressed.

“It’s not a question of being more or less afraid,” says Prof. Eilam. “Under threat, members of a social group will adopt a common behavioral code, regardless of their individual tendency towards anxiety.”

Another interesting finding, says Prof. Eilam, was the difference in group stress levels among an all-male group, an all-female group, and a mixed-gender group. Both female and male voles experienced heightened anxiety when exposed to barn owls in an all-female or all-male group but their response to stress changed in the mixed groups. The female voles in the mixed group exhibited a standard heightened anxiety level, says Prof. Eilam, but the males did not.

“This is an adaptive behavior that reflects work division within the family.”

While the studies focused on rodents, Prof. Eilam says that this research provides a model with which human group behavior can be assessed.