A bystander feels more empathy for someone in pain when that person is in the same social group, researchers in China said.

The study, published in The Journal of Neuroscience, showed that perceiving others in pain activates a part of the brain associated with empathy and emotion more if the observer and the observed are the same race.

The study confirms an in-group bias in empathic feelings, something that has long been known but never before confirmed by neuroimaging technology, the study said.

"Our findings have significant implications for understanding real-life social behaviors and social interactions," Shihui Han of Peking University in China said in a statement.

The researchers chose race as the social group, although the same effect may occur with other groups. The researchers scanned brains areas in one Caucasian group and one Chinese group.

The authors monitored participants as they viewed video clips that simulated either a painful needle prick or a non-painful cotton swab touch to a Caucasian or Chinese face.

When painful simulations were applied to people of the same race as the observers, the empathic neural responses increased. However, responses increased to a lesser extent when participants viewed the faces of the other group, Han said.