Also, game-designers could learn a lot from psychologists. Whenever I heard Bartle's taxonomy for the first time during a game studies course, my question was (and still is): why is a taxonomy the best way to capture this? In a personality research course it became clear to me that the biggest successful models are dimensional in nature (e.g. five factor model/big 5) they are not taxonomies.
I'd love for more psychologist/personality researchers to team up with game-designers. I think it could advance some scientific discoveries into human behavior.