Raw cognitive ability — at least performance on tests that measure it — isn’t nearly as difficult to enhance as many people think. When people believe they can get smarter, they do. But — and this is very important — when people believe that cognitive ability is difficult or impossible to change, they don’t get smarter.
A series of studies by Columbia University’s Carol Dweck shows that when people believe their IQ level is unchangeable, “they become too focused on being smart and looking smart rather than on challenging themselves, stretching and expanding their skills, becoming smarter. Dweck finds that most people believe either that intelligence is fixed or that it can be improved through effort and practice. People who see intelligence as fixed believe statements like “if you are really smart at something, you shouldn’t have to work hard at it,” don’t take remedial classes to repair glaring deficiencies, avoid doing things they are not already skilled at because it makes them look dumb, and derive less pleasure from sustained effort and commitment. After all, they believe, if you have to work hard at things, it means you aren’t that smart.
— Hard Facts by Jeffrey Pfeffer and Robert I. Sutton