This
video of a conversation between two experienced firefighters provides an excellent discussion of the value of TDGs in their profession. It also describes some of the theories that explain why TDGs are such a powerful means of preparing people to make difficult decisions in stressful situations.
These two interviews (
here and
here) with Gary Klein, a psychologist who has done a lot of work in this area, provide excellent introductions to this theory. (Dr. Klein calls it "recognitional primed decision making.")