My first thought was that the dogs were simply hitting on odors they were unfamiliar with (see list), but I'm not all that familiar with the training process.
Also, some documentary I saw indicated that the handlers can subtly urge the dogs to react as if they are hitting on something.
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And I guess it's a matter of human nature that if you're being a jerk, persons in authority may sit on you for a while under some stretched and strained excuse or another.
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Terry