Our brains may understand meteorology, but in our guts we still think that not carrying an umbrella will make it rain, a belief that was demonstrated in experiments by Jane Risen of the University of Chicago and Thomas Gilovich of Cornell.

“It is an irony of the post-Enlightenment world,” they conclude, “that so many people who don’t believe in fate refuse to tempt it.”

When told about an applicant to graduate school at Stanford who had been given a Stanford T-shirt by his mother, people assumed he would hurt his chances for admission if he had the hubris to wear it. And they believed that a professor was more likely to call on them in class if they didn’t do the assigned reading.

Even people who consciously reject superstitions seem to have these gut feelings, says Orit Tykocinski, a professor of psychology at the Interdisciplinary Center Herzliya in Israel. She found that rationalists were just as likely as superstitious people to believe that insurance would ward off accidents.