There is overwhelming scientific evidence that higher rewards lead to lower performance, except in the most non-cognitive tasks. The carrot-and-stick approach only works for tasks where the solution is obvious -- e.g. a mechanical task that requires no thinking.
Key to his argument are the results of numerous variation to the Duncker's Candle Problem.
The better motivators are intrinsic rather than extrinsic:
- Autonomy: the urge to direct our own lives
- Mastery: desire to do better and better at something that matters
- Purpose: service of something larger than ourselves.