People outperformed their friends at predicting how anxious they’d look and sound when giving a speech about how they felt about their bodies. But they did no better than their friends (or than strangers who had met them just eight minutes earlier) at forecasting how assertive they’d be in a group discussion. And when they tried to predict their performance on an IQ test and a creativity test, they were less accurate than their friends.
People know themselves best on the traits that are tough to observe and easy to admit. Emotional stability is an internal state, so your friends don’t see it as vividly as you do. With the most evaluative traits, you just can’t be trusted. You probably want to convince everyone—and yourself—that you’re smart and creative.
This is why people consistently overestimate their intelligence, a pattern that seems to be more pronounced among men than women. It’s also why people overestimate their generosity: It’s a desirable trait. And it’s why people fall victim to my new favorite bias: the I’m-not-biased bias, where people tend to believe they have fewer biases than the average American.
Adam Grant writing in the Atlantic