Have the individuals pair up and instruct them that they have one minute to arm wrestle as many times as they can. Whoever wins the arm wrestling match gets a piece of candy for every time they win.
So they arm wrestle and get their candy (instruct them not to eat it yet).
If they are willing to work together and just let each other win -- taking turns so each gets an equal amount of candy -- they also get A LOT of candy.
This shows how if we work together instead of against each other we can all have the reward and it is much greater!