If you ask everyone on a team how much they're contributing and total all its members' responses, it will probably come out to over 100%. That's because we have a nearly-universal tendency to exaggerate how much we have contributed to a project compared to other members of a group.

Understanding our tendency to over-value our own efforts and under-value those of others has the potential to improve not only relations with co-workers, but also the productivity of work teams.

People can get very upset when they feel their colleagues are taking credit for more work than they really do. Yes, there are people who do this because it's easier than actually doing the work, but this study suggests that much of it is unintentional.

If you are working as part of a team — and nearly all of us are at some time or another — your teammates are probably accomplishing a lot more than you give them credit for. And the bigger the team, the more likely you are to underestimate the contributions of the other people, according to a new study from the University of California at Berkeley's Haas School of Business.

Almost 700 MBA students, people you wouldn't normally expect to be math-challenged, were asked how much work each contributed to their study group. Their totals consistently came to over 100%. In groups with eight or more members, totals exceeded 140%.

Some of this can be chalked up to ego. People naturally tend to focus on their own accomplishments. But the researchers found that the larger the group, the harder it is to accurately take into account everyone's contribution, to wrap your mind around the whole project, so to speak.

There was nothing to be gained by the students intentionally over-claiming their contribution to the group. It just happened naturally. “People were surprised about the extent that over-claiming occurs. They think their reporting is accurate,” said Juliana Schroeder, the study's lead author, in a statement.

The study found similar results when researchers asked authors of academic papers how much each contributed to the paper. The more authors, the more apparent over-claiming there was. Two other experiments that looked at what happens when you directly change the size of a group found the same effect.

Schroeder suggests ways to reduce over-claiming: “When you have large groups, you might want to consider breaking down the group into smaller teams,” she says. “It is also important to make the workflow very clear. If assignments are clearly divided, it's easier for people to remember who is doing what.”

People can get very upset when they feel their colleagues are taking credit for more work than they really do. Yes, there are people who do this because it's easier than actually doing the work, but this study suggests that much of it is unintentional. Yet those who feel like they have contributed more than others (nearly everyone) are quite likely to be disappointed by the recognition they receive.

Schroeder suggests that people might want to think of other's contributions before thinking of their own. That should help combat the natural tendency towards egocentrism. While it might stop people from giving themselves a big hand, it's also likely to give them a clearer idea of the project's big picture.

The study appears in the Journal of Experimental Psychology: Applied.