I have a student in class that I really do enjoy talking to, but I have trouble keeping him on task. As soon as he gets to challenging question in our lab work, he starts making jokes and talks about how there's no way he will ever be able to do the work. I've tried playing along, ignoring the behavior and I had a one-on-one frank discussion with him about his actions. His joking interferes with his ability to receive redirection and new information. He agreed that he uses humor as a defense mechanism and he admitted the he didn't think it was helpful. After our conversation he went right back to his old behavior! He really is talented and capable...any suggestions about how I can help him stop hiding behind his humor?