Trick for more Tips

The new issue of the magazine Wired has an interesting idea that I will be looking to try: Research shows that the picture of a face or simply eyes on a donation jar for the office coffee or a tip jar will raise the contents of the jar over 30 percent.

Apparently, even though it is just a picture, subconsciously the idea that one is being watched is apt to increase one's generousity.

I wonder if putting a picture of eyes on a time sheet to payroll will have the same effect?