We are often surrounded by bogus claims about other people—especially in the context of political elections. But why do we sometimes believe blatant misinformation? A new study from the University of Arizona suggests that our gullibility can be triggered by subtle reminders of how we are different from the person in question.

During the months before and after the 2008 presidential election, psychologist Spee Kosloff and his colleagues asked predominantly white, non-Muslim students to evaluate smears about both candidates. They found that cues about social differences, such as age or race, were enough to get many participants to buy into false allegations against a candidate. Students who were undecided about which candidate to support, for example, when asked to report their own race on a questionnaire, increased their belief that Barack Obama was Muslim from 38 to 58 percent. Similarly, reminding students about their own age helped to make them believe that John McCain was senile. Overall, thinking about differences in social categories in­creased students’ acceptance of smear-campaign misinformation by 24 percent, Kosloff says.

Scientists have long known that we tend to have a preference for people of our own social category, “an us-versus-them sort of mentality,” Kosloff says. But he adds that he was surprised by the magnitude of this effect in his experiments. He plans to use upcoming elections to look at ways to counter the effect, for example, by reminding people of similarities they have with a candidate. To wit, “I am an American; he is an American. Would that reminder attenuate people’s willingness to believe that [Obama] is Muslim?” Kosloff asks.