A large meta-analysis of feedback studies found that in more than a third of cases, feedback actually lowered performance.
The sign of the feedback — praise or criticism — didn’t predict the outcome. The direction of attention did. Feedback about the task (what the correct answer is, how the work has progressed) tended to help. Feedback that pulled attention toward the self — praise of the person, or threats to their self-esteem — tended to weaken or reverse the effect.
People can act on information about work. Judgements about themselves mostly trigger defence.