@rbender
You are probably right - giving me a raise probably won't motivate me to be a better worker, but I wouldn't mind testing the theory a couple of dozen times - just to be sure.
The reality is that money is never a source of satisfaction (or motivation) at work, it is only a source of dissatisfaction. That 'good feeling' we get after receiving a raise is ephemeral. It only lasts a few pay cycles and then its gone. However if we feel like we're underpaid then the dissatisfaction is unrelenting.