Most of us delude ourselves that we are either too ethical to indulge self-interest, or too wealthy and important to allow ‘minor’ perks to sway us.

We humans are a sneaky species, but research into how other animals feign death and deceive mates shows we are not alone in our slyness. What may be unique about us is the ability to delude ourselves.

“Self-interest is automatic, viscerally compelling, and typically unconscious,” writes Carnegie Mellon psychology professors Don A. Moore and George Loewenstein in a 2004 research report.

It’s no biggie to believe that chocolate isn’t fattening, but we want the people protecting health and safety to choose public good over private interests—and to know the difference between the two. Conflicts of interest are pervasive—from doctors offered drug company-sponsored “educational” trips to Bali, to outside accountants hired to check corporate books or rate credit-worthiness, to inspectors who certify health and labor conditions for clients. While other more venal souls might be seduced, most of us delude ourselves that we are either too ethical, or too wealthy and important to allow “minor” perks to sway us.

University of Minnesota medical researcher Dr. Richard Grimm believes he was uninfluenced by the $800,000 that drug companies paid him while he served on government-sponsored panels to create guidelines for prescribing blood pressure pills. “There’s this automatic assumption that if you make money from a drug company, you must be corrupt,” Grimm recently told the New York Times, presumably asserting he was not.

Lewis Morris does not believe in moral fairy tales, even when told by a Grimm. “Somehow physicians think they’re different from the rest of us,” the chief counsel to the inspector general of Health and Human Services told the Times. “But money works on them just like everybody else.”

Some people seem oblivious that they have a conflict. In defending MSNBC hysteric Jim Cramer against Jon Stewart, Washington Post columnist Richard Cohen noted that his own “(extremely) hard-earned retirement funds” were in AIG stock. I sent several e-mails to Cohen, asking if he considered it a conflict of interest for a journalist who writes about financial issues to own individual stock, or if he had disclosed his holdings to either the public or his editors. No reply.

Among those with the hubris to sneer that their reward was too small to sway them is a Supreme Court justice. While the high court was dealing with a case concerning Dick Cheney, the VP flew his longtime buddy Antonin Scalia on a duck-hunting trip. “If it is reasonable to think that a Supreme Court justice can be bought so cheap, the nation is in deeper trouble than I imagined,” Scalia sniffed—which, while ignorantly accurate, was unethical given that federal law requires a judge’s recusal “in any proceeding in which his impartiality might be questioned.”

Some conflicts of interest produce outright corruption. From 2002 to 2007, while Pfizer was underwriting much of Dr. Scott S. Reuben’s research, the Massachusetts anesthesiologist fabricated data showing that Pfizer’s asprin-like drugs, including Bextra, Celebrex and Lyrica, are effective against postoperative pain. Who knows how many patients endured unnecessary pain and retarded outcomes because of Reuben’s fictional data.

How do people with conflicts of interest sleep at night? Pretty well, thinks psychology professor Paul Thagard. “People naturally have personal goals that may conflict with their professional responsibilities,” he writes, but they “usually remain unaware that they are acting immorally.”

Blame it on the brain or the devil, but the cost in blood and treasure is massive. Big Pharma’s seductions promote useless, expensive and dangerous drugs. Firms such as Standard & Poor’s and Moody’s handed out AAA ratings to mortgage securities that were terribly risky. Private inspectors from the American Institute of Baking rated “superior” the peanut factory that spread salmonella, killing nine, sickening 22,500.

What to do? Regulations and penalties don’t work for people who won’t recognize a conflict of interest, or who bet short-term gain over possible penalty. Nor does disclosure of potential conflicts preclude abuse. Disclosers may gain “exaggerated confidence that they are acting morally, and are therefore impervious to the effects of conflicts of interest,” writes Thagard, while those who read the disclosure get false reassurance that the info is impartial.

Because motivations are murky—even to ourselves—the best strategy is not only legally barring conflicts of interest, but also the appearance of them.