Great talk by Dan Pink at TED about pitfalls of extrinsic stimulus and scientific evidence for intrinsic motivation:
I kind of always felt that way, but now I've got evidence to refer to. Plutarch was right that
The mind is not a vessel to be filled but a fire to be kindled.
You can not stimulate creativity, you can only create environment for it to blossom.
If you are a manager, you've got everything to prevent this sign from ever appearing near the entrance to you department's area.