The students who were initially praised for their effort worked hard at figuring out the puzzles. Kids praised for their smarts, on the other hand, were easily discouraged. Their inevitable mistakes were seen as a sign of failure: Perhaps they really weren’t so smart. […] In contrast, kids praised for their hard work were more interested in the higher-scoring exams. They wanted to understand their mistakes, to learn from their errors, to figure out how to do better.

My aunt (an award winning teacher) told me about this a few years ago and I’ve tried to make sure it colors how I communicate with my daughter.

(thanks Ben)