There is a box on the coffee counter in the Psychology Department at the University of Newcastle. On the wall above it, a note shows the prices for coffee and tea, and explains that payment should be left in the box. That’s been the system for years.
However, for 10 weeks in 2006, Melissa Bateson and her colleagues placed an image above the note. Every week they changed the picture, alternating between images of eyes and flowers. They tracked the amount of money received versus the amount of liquids consumed each week and plotted the results in this graph. Nearly 3 times as much money was collected on weeks when the eyes were watching. This graphic from their report shows the picture used each week and the income it generated.