In each of two experiments, college students were assigned to two ad hoc groups that competed in a dart-throwing contest. On each trial, one contestant from each team threw a single dart at a standard dart board, trying to come as close as possible to hitting the bull's-eye. Also on each trial, the other participants judged the likelihood that both the Team A contestant and the Team B contestant would come closer to hitting the bull's-eye. In both experiments, participants exhibited (...) a strong wishful thinking effect. They judged the likelihood that their own team members would come closer to be greater than the likelihood that the opposing team members would come closer. Experiment 2 suggested that it was participants' desires, as opposed to some other variable associated with team membership, that influenced their predictions. Experiment 2 also showed that the size of the effect did not depend on whether participants believed that their predictions had been influenced by their team membership. These results help bridge the gap between previous experimental laboratory studies, which have produced inconsistent results, and correlational field studies of sports fans and voters, which have consistently produced large effects. (shrink)