This TED talk by Daniel Pink presents some counter-intuitive and interesting research on the relationship between motivation and performance in problem solving/creative thinking jobs.

More money or more threats only work on simple process-based jobs. Extrinsic motivation only works when the work does not really matter beyond doing it.

Intrinsic motivation, doing something because it is meaningful, because it matters, is what is needed to motivate the new set of idea workers. Where work is designed around Autonomy, Mastery and Purpose.