Anyone can participate in this experiment, anywhere, anytime (more than once!).

The premise is as in the movie Pay It Forward.

It starts when someone does something really nice for another person.

You start; you do something really nice and unexpected for someone you hardly know. When the recipient/s of your kindness want to show gratitude back to you, you simply ask them to "pay" their gratitude "forward" by going out and doing something wonderful for three more people whom they hardly know, without a vested interest.

If it helps you can refer them to “The Love Experiment” website and to the movie Pay It Forward.