This article  from the Journal of Bone and Joint Surgery is pretty interesting. It presents results from an outcomes investigation that was performed to compare physicians'
performance and attitude in a procedure-related CME activity.
The kicker is that while they found a correlation between increased confidence and
improved performance, but there was an even greater correlation between
increased confidence and their personal perception of improvement. As an alert reader who gave me a heads up on this article said in an e-mail, "A skeptic
might observe that, while CME improves doctors' performance, it also makes them
develop a false sense of confidence." (Thanks, Irwin!)