Even very smart people can feel and act and appear less smart than they are. Scores of psychology experiments show the role ability stereotypes play in this process, leading perceivers to see stereotype targets as more or less qualified depending on the stereotype. For targets awareness of such stereotypes can either impair or boost performance depending upon the particulars of the situation and the past experiences of students. I discuss implications of this research for both self improvement as well as difficult social problems such as the achievement gap between blacks and whites and the math gap between males and females.