A family friend related this story of his experience in the army:

He was an officer assigned to teaching enlisted men elementary code-breaking. He worked at one of several facilities designated for that purpose, but his students consistently outperformed students at other facilities. So one day the brass came to inspect and inquire as to the methods being used. They wanted to see if there was something unique going on that could be applied at all of the schools.

He and the other teachers there confessed that they didn't know why their students were doing so well. They were following the standard instruction course as outlined in the manual, etc. Maybe they had gotten the better students, they suggested. The brass were pleased with their work but left mystified as to why the students there were doing so well.

Well, what our friend didn't tell his superiors was that the encoded texts they were giving to the students to decipher were all pornographic! Thus the young men were considerably more motivated to decipher the texts than they would have been otherwise. I think it was a brilliant tactic, but I think I too would have been reluctant to reveal it to the regular army brass as they might not appreciate it.