However, friendship with a victim does not make people generally more sympathetic, said study authors Deborah A. Small and Uri Simonsohn, both of the University of Pennsylvania.

"The sympathy inherent to a close relationship with a victim extends to other victims, leading benefactors to prefer charities that help those suffering from the misfortunes that have affected their friends and loved ones," the study authors said in a statement.

In one study, the researchers interviewed strangers in a train station about their feelings about Alzheimer's disease, breast cancer and job layoffs. They found that people who were closer to someone who had experienced one of the misfortunes were more sympathetic to the victims of those, but not to victims of the other misfortunes.

Surprisingly, in subsequent studies the authors were able to recreate this phenomenon in an experiment in which friendships were newly created and the misfortune was losing $10. After people became "friends" in the study, they were more likely to donate money to a friend who lost money.

The findings are published in the Journal of Consumer Research.