Despite extensive studies proving sugar has no link with hyperactivity, I am convinced my daughters almost weekly decline into a manic, frenzied little monkey is a direct result of the masses of chocolate and sweets her grandparents feed her.
The scientists will suggest it is her environment, ie her excitement at being at her Grandparents, but she is "normal" all day with them until the treats are given, at which point she becomes a little monster.
This is one I really believe the scientists have got wrong. Surely caffeine in chocolate would stimulate a child and sugar would provide a quick high.