Good point. A simple fix would be to figure out what a normal score on the exercise would be without cookies. If it's the same as with cookies (or close), it's

Good point. A simple fix would be to figure out what a normal score on the exercise would be without cookies. If it's the same as with cookies (or close), it's safe to conclude that it's the temptation of the cookies moreso than the sugar that makes the difference. They might have actually done this.