I love the red haired girl. She's got the marshmallow in her mouth while the woman's instructing her. I agree, a real go-getter, that one.
I thought about them giving them a distraction, especially considering as adults that's how we manage a lot of the difficulties in our lives. However, I think the purpose of the study stages child against marshmallow-- the torture principal. A bare room, with no distractions, only the child's ability to keep him or herself occupied in the face of tempatation.