In The Empire Strikes Back, when Yoda is training Luke to be a Jedi, he demonstrates the power of the Force by raising an X-wing fighter from a swamp. Luke mutters, “I don’t believe it.” Yoda replies, “That is why you fail.”

As usual, Yoda was right—and science backs him up. Numerous studies have proved that confidence is the real key to success.

Studies exploring the performance gap between men and women in math and spatial skills have found that confidence plays a huge role. Women who were asked to identify their gender before taking a spatial skills test performed more poorly than those who weren’t.

 Women also performed better when they were told to envision themselves as men, and both genders performed better when they were told that their gender is better at the task.

What’s even more interesting is that the gender gap practically disappeared when participants were required to answer every question. Apparently, when the women were allowed to skip questions, they did so not because of a lack of knowledge, but because of a lack of confidence.

True confidence is very different from egotistical swagger. When people believe in themselves and their abilities without bravado, there are certain things they simply don’t do.

1. They don’t make excuses

2. They don’t quit

3. They don’t wait for permission to act

4. They don’t seek attention

5. They don’t need constant praise

6. They don’t put things off

7. They don’t pass judgment

8. They don’t avoid conflict

9. They don’t let a lack of resources get in their way

10. They don’t get too comfortable

Travis Bradberry is the coauthor of Emotional Intelligence 2.0 and the cofounder of TalentSmart.This article originally appeared on LinkedIn.