Fans of different soccer teams are often sworn enemies — but would they go so far as to refuse to help a rival fan in pain?

Grit Hein at the University of Zurich in Switzerland and her colleagues used functional magnetic resonance imaging to scan the brains of fans of two rival football teams, identified by coloured wristbands (pictured). The volunteers watched either a fellow fan or a rival receive a painful electric shock to their hand. Fans could then choose to help the other person by enduring half the pain themselves, or to watch either the person endure the pain, or a video about football.

Activity in two different brain areas predicted fans' reactions. In those that chose to help, a region associated with empathy called the anterior insula was activated. By contrast, in those that let their rival suffer, the nucleus accumbens showed activation — which was stronger if they had rated that particular foe more negatively before the test.

Credit: S. LEIBERG

Neuron 68, 149–160 (2010)