In 2014, a team of psychologists found that feedback could be 40% more effective by prefacing it with these 19 words:

“I’m giving you these comments because I have very high expectations and I know that you can reach them.”. This is in contrast to the traditional feedback sandwich, where constructive criticism is masked between two layers of compliments. Not a great way of giving feedback, it turns out. If anything, feedback sandwiches benefit the giver more than the receiver, as they feel that no feelings have been hurt.

A 40% increase is a lot, especially for just a few seconds. I think part of the effectiveness lies in:

1. Knowing that the feedback is genuine, with no artificial compliments.
2. Feeling that somebody is truly behind your back.

A much better formula for constructive feedback.