This is a superb video that outlines research into money as a motivator. The basic premise is that simple tasks that are fully prescriptive respond well to bonus etc. This makes sense as the only real differentiator is attention to detail and concentration.
But for work that requires creativity and mental effort, higher financial rewards actually reduce performance. I sh*t you not!
But you really need to see how this is explored and I will leave you in the dark on the last bit of research on what really motivates what we might call knowledge-workers – programmers, writers, etc …
Update: When I first published this, I forgot to add the following important point: extra money is not a motivator, but a perceived lack in one’s compensation (which I believe can include either a too-low salary, or some other sleight when compared with coworkers) is a definite de-motivator. Also, poor working conditions, crappy tools (e.g. old laptops) … anything that sucks the fun out of the work day.