Ever watched someone grimace after they sniffed a carton of sour milk? Even though you were spared a whiff of stinky milk, to your brain, you might as well have been sniffing the milk yourself, a report from Italy suggests.

New research shows that when we see an expression of disgust on someone else's face, the same part of our brain -- the insula -- is activated as when we feel disgust ourselves.

"People have overemphasized the importance of thoughts in our understanding of others," Dr. Christian Keysers of the University of Parma, a co-author of the report, told Reuters Health.

Although Keysers said that empathy for others is often thought of as a matter of morals, "in our study, on the other hand, we show that empathy is a very basic, simple and automatic process," he said.

Keysers explained that when we see the emotions on another's face, "we don't need to think about how that person feels." Instead, according to Keysers, we share the feeling of disgust because the insula is activated as if we were disgusted ourselves.

"This sharing is automatic," he said. "Our subjects were not asked to share the emotion of the other person and did not report attempting to do so after the scan. It just happens."

Keysers continued, "This shared feeling of disgust could then be our key to understanding how the other person feels."

Researchers used a tool called functional magnetic resonance imaging (fMRI) to monitor the brain activity of 14 men as they watched short movies of people smelling pleasant, disgusting and neutral odors. Brain activity was also monitored while participants themselves smelled a variety of odors.

The researchers found that a part of the brain called the anterior insula, which previously has been linked to feelings of disgust, was activated not only when participants smelled something disgusting but also when they watched others take a whiff of something stinky.

A report on the findings is published in the October 30th issue of the journal Neuron.

"We implicitly understand the meaning of the actions of others and the meaning of their emotions by simply stimulating them," Dr. Giacomo Rizzolatti, another of the study's authors, told Reuters Health.

"What we provide is a neurophysiological characterization of empathy," said Rizzolatti.

The next step, according to Rizzolatti, will involve studies of schizophrenia and autism to see to what extent malfunctioning in the ability to mirror the emotions of others is to blame for difficulties in establishing meaningful relationships with other people.

SOURCE: Neuron, October 30, 2003.

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