The makers of Volkswagen have developed a fairly interesting "theory" about human behavior: if you make something fun, you can change people's behavior for the better. They call this The Fun Theory and have dedicated a website to demonstrating how it works.
In the first video of the website, they demonstrate how pedestrians leaving a train station can be induced to walk up stairs instead of taking the escalator next to the stairs. Normally people would choose the escalator because it takes less personal physical energy to leave the train station. However, it would be better for more people to take the stairs. In general, it is healthier to walk up the stairs because it is exercise. Furthermore, it would also be better for the environment if more peopled walked up the stairs because it takes up less energy.
As can be seen in the video, they have two scenarios in their experiment: (1) regular stairs next to an escalator, and then (2) "piano" stairs next to an escalator. The piano stairs are painted like a piano and make sounds when walked on. The results of this experiment are very impressive. Many more people choose to walk up the stairs when they were "piano" stairs than regular stairs. In the end, 66% more people walked up the stairs in the second scenario than the first scenario.
I highly recommend checking out the site and the other experiments on the site. They are also launching a contest next week, so stay updated. Contestants in this contest can submit ideas for new, creative, and of course fun ways to change human behavior for the better. They are even giving away cash prizes for the winners.