In a series of recent studies, a team of researchers led by Peter H. Kim of the University of Southern California and Donald L. Ferrin of the University of Buffalo, now at Singapore Management University, had groups of business students rate the trustworthiness of a job applicant after learning that the person had committed an infraction at a previous job. Participants watched a film of a job interview in which the applicant was confronted with the problem and either denied or apologized for it.

If the infraction was described as a mistake and the applicant apologized, viewers gave him the benefit of the doubt and said they would trust him with job responsibilities. But if the infraction was described as fraud and the person apologized, viewers’ trust evaporated — and even having evidence that he had been cleared of misconduct did not entirely restore that trust.

“We concluded there is this skewed incentive system,” Dr. Kim said. “If you are guilty of an integrity-based violation and you apologize, that hurts you more than if you are dishonest and deny it.”

The system is skewed precisely because the people we rely on and value are imperfect, like everyone else, and not nearly as moral or trustworthy as they expect others to be. If evidence of this weren’t abundant enough in everyday life, it came through sharply in a recent study led by Dan Ariely, a behavioral economist at the Massachusetts Institute of Technology.

Dr. Ariely and two colleagues, Nina Mazar and On Amir, had 326 students take a multiple-choice general knowledge test, promising them payment for every correct answer. The students were instructed to transfer their answers, for the official tally, onto a form with color-in bubbles for each numbered question. But some of the students had the opportunity to cheat: they received bubble sheets with the correct answers seemingly inadvertently shaded in gray. Compared with the others, they changed about 20 percent of their answers, and a follow-up study demonstrated that they were unaware of the magnitude of their dishonesty.

“What we concluded is that good people can be dishonest up to the level where conscience kicks in,” said Dr. Ariely, author of the book “Predictably Irrational: The Hidden Forces that Shape Our Decisions,” due out next year. “That essentially you can fool the conscience a little bit and make small transgressions without waking it up. It all goes under the radar because you are not paying that much attention.”

It is a mistake to underestimate the power of simple attention. People can be acutely aware of what they pay attention to and remarkably blind to what they do not, psychologists have found. In real life, to be sure, casual denials of bad behavior require more than simple mental gymnastics, but inattention is a basic first ingredient.