When was the last time you cheated?

Not on the soul-scorching magnitude of, say, Bernie Madoff, Lance Armstrong or John Edwards. Just nudge-the-golf-ball cheating.

Maybe you rounded up numbers on an expense report. Let your eyes wander during a high-stakes exam. Or copied a friend’s expensive software.

And how did you feel afterward? You may recall nervousness, a twinge of guilt.

But new research shows that as long as you didn’t think your cheating hurt anyone, you may have felt great. The discomfort you remember feeling then may actually be a response rewritten now by your inner moral authority, your “should” voice.

Unethical behavior is increasingly studied by psychologists and management specialists. They want to understand what prompts people to abrogate core values, why cheating appears to be on the rise, and what interventions can be made. To find a powerful tool to turn people toward ethical decisions, many researchers have focused on the guilt that many adults feel after cheating.

So some behavioral ethics researchers were startled by a study published recently in The Journal of Personality and Social Psychology by researchers at the University of Washington, the London Business School, Harvard and the University of Pennsylvania. The title: “The Cheater’s High: The Unexpected Affective Benefits of Unethical Behavior.”

“Showing people feeling positively after committing a moral transgression is pretty novel,” said Scott Wiltermuth, an assistant professor in the business school at the University of Southern California, who writes about behavioral ethics and was not involved in this study.

One reason for pervasive garden-variety cheating is “that we have so many ways to cheat anonymously, especially via the Web,” Wiltermuth said. The exhilaration, he added, may come from “people congratulating themselves on their cleverness.”

The impact is real: According to some estimates, software piracy costs companies $63 billion a year globally. The Internal Revenue Service has reported an annual gap between actual and reported taxes of about $345 billion, more than half of that because incomes are underreported and deductions inflated.