Ok, Professor Noggin's was extremely hard to rate. Here's why: in terms of learning...it would be a solid 9, easy. Cool facts. But once you have been through a pack a couple of times...it's time to move on. We started shuffling some decks together which has helped provide variety and stops the ability of just simply "memorizing" the right answers. However, it doesn't shuffle as well together as let's say, the Timeline series, which was made to be shuffled together and is a little easier, and more thematic to do, since it deals with dates and putting stuff in the right numerically dated order (which sounds boring, but actually is pretty fun).