Six studies demonstrated that praise for intelligence had negative consequences.

The American Psychological Association published this study in 1998, in the Journal of Personality and Social Psychology. The writers are Claudia Mueller and Carol S. M.Dweck. ‍

Most of this study is behind a paywall, but here is the free blurb.

Praise for ability is commonly considered to have beneficial effects on motivation. Contrary to this popular belief, six studies demonstrated that praise for intelligence had more negative consequences for students' achievement motivation than praise for effort. Fifth graders praised for intelligence were found to care more about performance goals relative to learning goals than children praised for effort. After failure, they also displayed less task persistence, less task enjoyment, more low-ability attributions, and worse task performance than children praised for effort. Finally, children praised for intelligence described it as a fixed trait more than children praised for hard work, who believed it to be subject to improvement. These findings have important implications for how achievement is best encouraged, as well as for more theoretical issues, such as the potential cost of performance goals and the socialization of contingent self-worth.

The link to pay (just $17.95) to read the entire article can be found here.