This video below is very interesting. The first few minutes is what I was interested in. (So if you are busy, watching only the first few minutes is fine.)
They did a few studies where they asked people to preform tasks and gave them financial rewards based on performance. (Like Wall Street does and swears by.) They found that for menial tasks, this type of motivation worked great. However, as soon as the task required an above average amount of cognitive ability, financial rewards actually have negative consequences!
Anyways, a very interesting video to watch, especially if you have been trapped into the unproven claim that money is the best motivator.