In the 1970s, the gift shop at the Kennedy Center for the Performing Arts was an informal affair. It was staffed by about 300 mostly elderly volunteers, and there were cash drawers instead of registers. The problem was that of the shop’s $400,000 in annual revenue, somebody was stealing $150,000.

Dan Weiss, the gift shop manager at the time who is now the president of Lafayette College, investigated. He discovered that there wasn’t one big embezzler. Bunches of people were stealing. Dozens of elderly art lovers were each pilfering a little.

That’s one of the themes of Dan Ariely’s new book “The (Honest) Truth About Dishonesty.” Nearly everybody cheats, but usually only a little. Ariely and his colleagues gave thousands of people 20 number problems. When they tackled the problems and handed in the answer sheet, people got an average of four correct responses. When they tackled the problems, shredded their answers sheets and self-reported the scores, they told the researches they got six correct responses. They cheated a little, but not a lot.

That’s because most of us think we are pretty wonderful. We can cheat a little and still keep that “good person” identity. Most people won’t cheat so much that it makes it harder to feel good about themselves.