One interesting, but hardly surprising, cognitive bias is the tendency of a person to regard herself as better than average—even when no evidence exists for that view. Surveys in which Americans are asked to compare themselves to their fellows are quite common and nicely illustrate this bias: the overwhelming majority of Americans rank themselves as above average in everything ranging from leadership ability to accuracy in self-assessment.
Obviously enough, the majority of people cannot be better than average—that is just how averages work. As to why people think the way they do, the disparity between what is claimed and what is the case can be explained in at least two ways. One is another well-established cognitive bias, namely the tendency people have to believe that their performance is better than it actually is. Teachers get to see this in action quite often—students generally believe that they did better on the test than they actually did. For example, I have long lost count of people who have gotten Cs or worse on papers who say to me “but it felt like an A!” I have no doubt that it felt like an A to the student—after all, people tend to rather like their own work. Given that people tend to regard their own performance as better than it is, it certainly makes sense that they would regard their abilities as better than average—after all, we tend to think that we are all really good.
Another reason is yet another bias: people tend to give more weight to the negative over the positive. As such, when assessing other people, we will tend to consider negative things about them as having more significance than the positive things. So, for example, when Sally is assessing the honesty of Bill, she will give more weight to incidents in which Bill was dishonest relative to those in which he was honest. As such, Sally will most likely see herself as being more honest than Bill. After enough comparisons, she will most likely see herself as above average.
This self-delusion probably has some positive effects—for example, it no doubt allows people to maintain a sense of value and to enjoy the smug self-satisfaction that they are better than most other folks. This surely helps people get by day-to-day.
There are, of course, downsides to this—after all, a person who does not do a good job assessing himself and others will be operating on the basis of inaccurate information and this rarely leads to good decision making.
Interestingly enough, the better-than-average delusion holds up quite well even in the face of clear evidence to the contrary. For example, the British Journal of Social Psychology did a survey of British prisoners asking them to compare themselves to other prisoners and the general population in terms of such traits as honesty, compassion, and trustworthiness. Not surprisingly, the prisoners ranked themselves as above average. They did, however, only rank themselves as average when it came to the trait of law-abidingness. This suggests that reality has some slight impact on people, but not as much as one might hope.