When an owner creates a stimulus that tells the dog that something unpleasant is about to happen. A safety signal, for example, tells the dog that something unpleasant is not going to happen. For example, the collar component of an invisible fence will beep when the dog is approaching the boundary area, where he will be shocked. The dog learns that the beep precedes the shock, and can then avoid the shock. According to the safety signal hypothesis, the beep could become positively reinforcing because it is associated with avoidance.
In an experiment, psychologists found that rats strongly preferred to be in a situation where an electric shock was signaled by a sound, even when the rats couldn’t avoid the shock. The experimenters suggested that this was because the sound was a signal the rats could use to predict safe and unsafe periods of time, and the predictability was something the rats preferred.
Badia, P and S. Culbertson (1972). The relative aversiveness of signalled vs. unsignalled escapable and unescapable shock. Journal of the Experimental Analysis of Behavior 17(3), pp.463-471.