When the dog decides to bark, it is critical that at that instant it is immediately rewarded with the helper trying to flee in prey with the dog chasing and getting a non-threatening prey bite. It's also very important that when this moment of insecurity happens, the handler remains quiet and away from his dog. This work is between the helper and dog and nothing to do with the handler. Just as importantly, it is a mistake for new helpers to stay in the blind and expect the dog to bark and bark for an extended period of time. The key to this training step is to immediately react to the change of drives and the first bark.
Timings are critical.
The first stages of this work requires some decisions being made concerning the level of maturity and level of prey drive development in the young dogs. The dogs must be mature enough to handle the stress of defensive work. While some dogs with good working genes and a sound foundation in prey development can handle the stress of early defense work at 12 months, others may have to wait until 18 to 24 months. Some German show lines and ALL American bloodline dogs can never handle it. At the beginning of this training almost every young dog will back off and act a little insecure.