"One of the most interesting bits of American research to surface—repeatedly—in books about happiness is a study that shows depressives are far more likely to be realists, while happy people are more likely to walk around in a mild state of delusion. The study itself was fairly simple: A group of undergraduates was given varying degrees of control over turning on a green light. Some members of the group had perfect control; others had none—the light went on and off of its own accord. The depressives accurately predicted, in each instance, whether they were in control of the situation or not. The nondepressives, on the other hand, thought they had control about 35 percent of the time over the situation in which they were, in fact, 100 percent helpless."