July 13, 2006
Rodents and humans have a link in shared suffering.
Pets, homeowners and pest exterminators show little sympathy to rodents, but that does not mean the little scavengers lack feelings for one another.
Last week, scientists studying the experience of pain in mice found strong evidence of empathy in those who saw a fellow creature suffering.
In a series of experiments, neuroscientists demonstrated that mice suffered significantly more distress when they saw a familiar mouse suffering than when they saw the same kind of pain in a stranger.
Experts call this shared suffering "emotional contagion" and consider it a primitive and necessary precursor to human empathy.
Apes, including orangutans and chimps, show clear understanding for the suffering of others in their clans and help them; elephants and dolphins also show some of the same instincts. But the new study is the first clear demonstration of sensations of shared suffering in mice, experts say.
"This is a highly significant finding and should open the eyes of people who think empathy is limited to our species," says Frans B.M. de Waal, a primatologist at Emory University in Atlanta and the author of Our Inner Ape.
Jeffrey S. Mogil, a neuroscientist at McGill University in Montreal, and a team of researchers studied how mice experienced discomfort under several conditions. In one, the scientists injected a pair of mice in view of each other with a chemical solution that caused a 30-minute stomach ache.
The mice squirmed significantly more when the partner was an animal with whom they shared a cage - a familiar mouse - than when the partner was a stranger. The sight of a relative in discomfort also heightened the experience, but not much more so than seeing a cage mate squirm.
The only way the researchers could reduce this shared pain was by blocking the animals' views of one another. Mogil said the mice almost certainly sent chemical signals of distress but that "it appears that the message, 'I'm in pain', is transmitted strongly through vision."
"We think the mice are reading others' facial _expression, but we don't know for sure," he said.
Human empathy, which can be felt intensely in response to a letter from a friend or a story about a stranger, is built on this instinct to tune in to the misery of others, in the same way a baby will begin crying when it hears another baby crying.
- The New York Times