When I was younger, I had a friend who watched four children for a week when their parents went on a cruise. There was no cereal in the house, so they made a run to the store where my girlfriend let them pick out brightly colored fruity cereals--after all, fruit is better for them than chocolate, right? By the end of the week she was telling me stories I couldn’t believe. The ten-year old, usually so well-behaved, had major attitude problems after the first few days, while the four-year old spent much of her time in timeout, even going so...