The marshmallow experiment is a psychological test they did with little kids I think like in the 90s where the researcher gives a kid a marshmallow and then leaves the room, with the supposition that if the kid doesn't eat the marshmallow he can have two marshmallows in ten minutes. It's basically a test of inborn self control. And they tracked these kids and basically found that the ones who could hold off ended up being way more succesful in life than the more impulsive kids who ate the marshmallow.
But watch these little kids on the video. They encompass every single personality trait in the world and it's hilarious. And Katie Baker narrates the shit out of it.