It really is true: When our friends hurt, we hurt.
Research published in the journal Social Cognitive and Affective Neuroscience shows that the reason humans feel empathy toward friends is because we associate others close to us with our own selves.
"A threat to ourselves is a threat to our resources," study research James Coan, a psychology professor at the University of Virginia, said in a statement. "Threats can take things away from us. But when we develop friendships, people we can trust and rely on who in essence become we, then our resources are expanded, we gain. Your goal becomes my goal. It's a part of our survivability."
Coan and colleagues conducted fMRI brain scans on 22 young adults for the study. As the study participants were undergoing the brain scans, they were told that they were under threat of either receiving an electrical shock themselves, or that their friend or a stranger was under threat of being shocked.
Not surprisingly, the study participants' anterior insula, putamen and supramarginal gyrus brain regions -- which all play a role in responding to threats -- activated when they were threatened of being shocked themselves.
But interestingly, when the study participants were told that their friends were in danger of receiving an electrical shock, these brain regions activated in the same way as when they were threatened with the shock themselves. However, there was little brain activation in these regions when they were told the stranger was in danger of electrical shock.
"The correlation between self and friend was remarkably similar," Coan said in the statement. "The finding shows the brain's remarkable capacity to model self to others; that people close to us become a part of ourselves, and that is not just metaphor or poetry, it's very real. Literally we are under threat when a friend is under threat. But not so when a stranger is under threat."