Just to address the question of elimination of fear and doubt... This is fairly easy to draw out on a line. Alcohol does a pretty good job of eliminating fear and doubt, as well. There are other problems mixed in with alcohol use, but I spent many years drinking, and having fear and doubt removed from pretty much every interaction, every day. You can ask my friends and family what that was like. I agree though that it would be very interesting for studying decision making if tDCS could modify very specific features like fear or doubt from every individual in a group.
