You've got so many reasons to stay above-board at the office. Nice guys don't actually always finish last in the professional world, and your colleagues and supervisors will all appreciate someone who does the work and keeps clean about it. But now you've got one more reason to stay honest on the job: You seem more capable because of it.
Psychologists from Stanford University just published research about how we perceive dishonest or immoral people. Most of their study investigated minor but not insignificant transgressions, like shoplifting or cheating. We actually don't like people we class as immoral, rather than finding immorality in people we already dislike. Furthermore, the study also showed that despite our protestations, our opinion of a person's private behavior does reflect on how we see their work.
All of that comes together to influence our perception of people on the job. Less honest people are seen as less capable; the researchers speculate that may be because we think those people have low social intelligence, that they're not good at navigating social situations. But the study has a flip side, one that may or may not be encouraging.
Dishonest people with high social intelligence were seen as "Machiavellian, cunning, and strategic," according to a press release. It may explain why we're so compelled by stories of corporate malfeasance, but it's also true that poor treatment and bad behavior don't produce the best results, subjectively or objectively. So err on the side of doing the right thing, if you have the choice — you're actually more likely to be rewarded for it.