This has been around for some time but I just was introduced to it today. From HuffPo:
In the late 1960s, psychologist Walter Mischel performed a series of tests on preschoolers referred to as The Marshmallow Tests. Mischel would give a child a single marshmallow, then leave him or her alone in the room with it. Before he departed, he’d make each kid an offer: if they wanted to, they could eat it immediately — but if they waited for him to return, they’d get two marshmallows. The tests were designed to examine willpower and the mental processes behind delayed gratification. Watching kids go through the experiment can be poignant… and adorable. See the video below.