How can they really believe it helps their children retain information? I can't believe there were people willing to pay over $100 U.S. for this either! I guess child abusers worry about being posh.
As an unschooler, I have witnessed first hand how much a person can learn if the motivation comes from within. If it is something that interests you, drives your passions, learning is not a chore, but it feeds your soul.
True learning isn't prison like at all. If you want to kill your child's natural ability to use their curiosity, just force them to study something that doesn't mean anything to them. Only add the Study Ball if you want to go medieval.