"Why does an image of a pair of eyes motivate cooperative behaviour? While it is possible that the eyes were simply more effective than the flowers at attracting people's attention to the notice, we do not believe that this is the explanation for our findings. The participants had all been informed prior to the experiment that they were supposed to pay for their drinks. Furthermore, the notice was positioned such that it was not possible that anyone making drinks would fail to see it, irrespective of the image displayed.

Instead, we believe that images of eyes motivate cooperative behaviour because they induce a perception in participants of being watched. Although participants were not actually observed in either of our experimental conditions, the human perceptual system contains neurons that respond selectively to stimuli involving faces and eyes"
"reputational concerns may be extremely powerful in motivating cooperative behaviour."

An interesting read.
Exposing some of the basic conditions humans perceive themselves and life through.

Used to drink with a bloke who always left his glass eye in his beer when he went to the toilet. The fact that no one drank his beer tells you nothing really. The occasional additive went unnoticed, which told me that he was so confident that no one would touch it, it wasn't really tabasco he was tasting.