Great footage! Thanks for the extra links @jamesrathmell & @lejaclyn — to add another, here’s a wnyc radiolab episode about self control in adults: www.radiolab.org/2011/mar/08/
I did the marshmallow test for a 6th grade science fair project with some younger grades. It was an unscientific sampling, but the girls did a little better. Also, I remember one boy eating 2 tiny bites out of one.