I'd have to go with low average intelligence.
Obviously "dumb" won't work because they do have the capacity to memorize text and give talks, but I really don't see that the majority would be able to function outside the Org.
Wifey was out with the group the other day and they returned her for better or worse. Anyway one of the Elder's children, a 4 y/o boy, was with them and he got out to say hi and pet the cat.
His mother SCREAMED when she saw what he was about to do, and he stopped and told me very seriously "Daddy says the scarlet beast with horns is a cat and I can't play with them anymore"
PLEASE don't feed the Dubz