It's not dumb in an ordinary sense... thing of it as training, similar to training a dog. These people have been brought up for some or all of their lives getting a virtual swat on the nose if they go outside of the boundries of their religeous group.
http://nobelprize.org/educational_ga...lov/index.html
The mechanism is slightly more complicated, but in the end, you can get the reglious types to drool on command as well.