One of the ideas that has always fascinated me is altruism within random groups. The idea that if you do a good deed and others see it, they will also be more likely to do a good deed.
I have been testing this idea on my drive into work for a few months now. In a totally non scientific way, I have been alternately allowing people to cross past me at a junction and not letting them. When I let them cross, I keep an eye on the car behind me to see if they then let the next person through.
I would estimate that about 7 times out of 10, the person behind will let the next car through. When I don’t do it, then the car behind almost always follows suit and won’t let the someone past.