Social groups respond alike to common dangers: Study

Washington: Scientists have found that response to a perceived danger is not different from one animal or human to another, as previously thought.

David Eilam and Rony Izhar of Tel Aviv University designed a study to investigate the anxieties experienced by an entire social group.

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.

The results demonstrated 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.

Eilam said that this explains human behaviour in response to trauma or terror. These are times when people stand together and accept a general code of conduct, he said.

Eilam and his fellow researchers measured the anxiety levels of three groups of ten voles each. 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, said Eilam.

After a night of exposure to their natural predator, the voles were tested once again for anxiety. Now, researchers found that each vole was equally stressed.

According to Eilam, this result is surprising compared to the control group, in which each vole went through the stressful night in the owl’s enclosure individually.

When facing their predators alone, there was no common level among all thirty of the voles when it came to their stress levels.

While they showed heightened anxiety, it was directly in relation to their base level anxiety response, as measured before the first experiment.

"It’s not a question of being more or less afraid.”

"Under threat, members of a social group will adopt a common behavioural code, regardless of their individual tendency towards anxiety," said Eilam.

Another interesting finding was the difference in-group stress levels among an all-male group, an all-female group, and a mixed-gender group, said Eilam.

Though both female and male voles experienced heightened anxiety when exposed to barn owls in an all-female or all-male group, their response to stress changed in the mixed groups.

The female voles in the mixed group exhibited a standard heightened anxiety level, but the males did not, said Eilam.

The findings have been reported in the journals ‘Behavioural Brain Research and Neuroscience’ and ‘Biobehavioral Reviews’.