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by Robin Foster, PhD, CAAB  The first time that my young English setter visited the stable where I board horses he was overjoyed at the freedom to explore new sights, smells, and (yuck) tastes. After thoroughly investigating the horse stalls and chicken coop, his attention shifted to the horses themselves. As he ducked under the electric fence bordering the pasture, he let out an agonized yelp as his back touched the hot wire. He streaked toward me, tail tucked and eyes wide, and for the rest of the day he never strayed from my side. That electric jolt was probably the first pain he had ever experienced.
On a different occasion at the barn (never a dull moment!) as I was saddling my mare for a lazy summer afternoon trail ride, we were interrupted by the sound of thundering hoofs. Galloping up the lane was my friend Ann’s horse . . . without its rider! As soon as the horse reached a grassy spot near the barn, she stopped abruptly, let out a big sigh of relief, dropped her head and started grazing. Apparently a tractor had frightened the horse, who shied and bolted for home leaving Ann behind—dirty, annoyed, and luckily only a little bruised. What do these incidents have in common? The most obvious similarity is that in both cases the frightened animals ran away from danger. A somewhat less obvious similarity is that both animals also ran towards safety. I served as a safety cue for my dog, and the familiar farm was a safety cue for the horse. Importantly, the animals felt immediately relieved and relaxed in the the presence of the safety cue. The power of safety signals to inhibit fear and avoidance, and to promote relief and relaxation, was established decades ago in laboratory studies with rodents. The vast majority of behavior issues experienced by domestic animals are based in fear and anxiety, but safety signal training is not typically included in behavior modification protocols. In a review article currently in press in the Journal of Veterinary Behavior, Paul McGreevy et al. highlight the importance of safety needs in motivating in animal learning and the potential for safety signal training as a tool in the treatment of fear and anxiety in animals. Causes of fear and anxiety-based behavioral problems Some fears are learned through painful, unpleasant, or traumatic experiences. In animals we rarely know what the bad experience was, but by watching closely we can usually identify the stimuli or situations that the animal perceives as threatening and that may have been associated with the bad experience. In social animals, some fears may be learned by observing others reacting fearfully toward the danger cue. And some fears, such as wariness of unfamiliar individuals or novel objects, can emerge without experience through evolved or artificially selected genetic predispositions. A threatening stimulus or “danger cue” can trigger a progressive series of defensive reactions that include freezing, fleeing, and fighting. These behaviors are usually undesirable in a companion or working animal, but persist because fear is physically uncomfortable and the defensive reactions are effective at both reducing the fear and removing the threat. Animals with fear-based problems seem to get worse over time, possibly because, by reacting sooner, they minimize their exposure to the danger cue. Behavior modification for fear-based behaviors Owners often put off seeking professional help until their fearful animals do something unacceptable or experience veterinary problems associated with chronic anxiety. Behavior modification, sometimes in conjunction with anti-anxiety medication like fluoxetine or alprazolam, has proven very effective for reducing fear emotions and avoidance behaviors. The most common techniques for treating behavior problems rooted in fear and anxiety are classical counter-conditioning (CCC), operant counter-conditioning (OCC), and extinction, which includes a method of exposure and response prevention (ERP). Safety signal training is rarely employed. These techniques modify emotions and behavior through different mechanisms. CCC changes the meaning of the danger cue by pairing it with a high value treat (or other attractive stimulus). The animal begins to expect something good in the presence of the danger cue, and the fear is inhibited. Once the emotion is under control appropriate behaviors are much easier to train. OCC reduces the unwanted behavior by rewarding a different acceptable behavior when the danger cue is present, either using a high value treat (positive reinforcement) or by removing the danger cue (negative reinforcement). For example, when the danger cue is present (a stranger is approaching) and the dog looks up at the handler instead of lunging, looking up would be rewarded with a treat or by moving away from the danger cue. The logic behind OCC is that if the animal’s behavior is relaxed, calm emotions will follow. In practice CCC and OCC are typically used together. Extinction involves repeatedly presenting the danger cue without anything bad happening, and eventually the animal will learn that the danger cue does not predict danger. In theory, extinction seems like a simple technique but it is fraught with practical challenges. Extinction requires long exposures to the danger cue because brief exposures can increase fear through a process called incubation. To get the longer exposure may require physically preventing the animal from running away, barking, and lunging (ERP), which in practice is challenging at best, and may pose welfare and safety issues. Flooding is an extinction technique that exposes an animal to a high intensity of the danger cue until the animal relaxes (or stops trying to escape). Flooding can be effective, but it must be used selectively and cautiously. As an example of how flooding can backfire, I consulted on a case involving an Arabian horse that spooked at white plastic bags and had tossed his rider several times. Several months before I started working with the horse, a different trainer had recommended a flooding procedure: the horse was confined to his stall with 50 white bags with the idea that he would eventually get used to them. But instead the horse started whinnying and pacing frantically for about 5 minutes, and then kicked through the stall door and ran off. Not only was he hard to catch afterward, from that point forward he was even more fearful of white bags and refused to set foot into his stall. External inhibitors of fear and anxiety It’s important to distinguish safety signals from external inhibitors, which are things in the animal’s environment that help reduce fear or anxiety without any training. For example, background noise like an electric fan can reduce a dog’s anxiety about fireworks, and the presence of a calm mare can inhibit a young foal’s fear of humans. When the external inhibitor is another animal, it may be considered a form of social facilitation. As an example, I was assisting at a clinic where one rider was trying quite unsuccessfully to convince her horse to walk through an obstacle called a “car wash”, which is a wall of streamers. Pushing and pulling the 1200 pound animal was pointless, and the horse was not interested in carrots, so we recruited an experienced horse to demonstrate. After two or three passes closely following the relaxed leader through the streamers, the previously fearful horse willingly and leisurely walked through the car wash alone. As an important practical note, an anxious leader would have produced the opposite effect and increased the horse’s fear and avoidance of the obstacle. Training safety signals Safety cues are learned through experience by signaling the absence of a bad event or aversive stimulus. They are powerful inhibitors of fear and avoidance, and can override undesirable responses triggered by danger cues. This property makes safety signal training a promising addition to behavior modification protocols for treating fear-based problems in animals. Safety signals can be trained using two different techniques: discrimination and backward conditioning. In general, when the safety cue is present nothing bad happens (and a lot of good things may happen!). The most practical application of safety signal discrimination training is the “A+/B-/AB-” model; “A” is the danger cue, “B” is the safety cue, “+” is the presence of the aversive, and “-“ is the absence of the aversive. We can use the case of a dog that is fearful of strangers to illustrate the training protocol. First, let’s assume that the dog had some sort of bad experience with a stranger in the past (“A+”) and now reacts by lunging and barking at strangers. In safety signal training the dog learns that when the safety cue—usually its owner, but it could be a toy or a clicker sound—is present nothing bad ever happens (“B-”), even when a stranger is also present (“AB-”). In real-life situations we assume that the fear conditioning event (“A+”) already happened and do not need to repeat it during safety signal training! It’s also important to avoid pairing the safety cue with unpleasant stimuli or events, especially early in training (this is yet another reason against using punitive and dominance training methods, especially with a new pet). Some techniques currently used to treat fear-based behaviors may be effective in part by creating safety signals through discrimination training. For example, in Grisha Stewart’s Behavioral Adjustment Training (BAT), the handler exposes a dog to the threatening stimulus (danger cue) at a safe distance, where the dog is attentive and alert but not fearful. Because there is prolonged exposure to the danger cue and nothing bad happens when both the danger cue and handler are present, the handler may become a conditioned safety signal. Safety signals may also be learned through backward conditioning. In this process, the safety cue appears immediately after the aversive is removed and predicts a period of respite from the threat. Backward conditioning is more common in real-life experiences than in training, but it may play a role in negative reinforcement training. For example, a horseback rider typically applies leg pressure to get the horse to move forward or speed up. When the horse responds correctly the rider releases the pressure (negative reinforcement) and will often say, “Yes!” or “Good girl!” Because the verbal cue occurs immediately after the pressure is removed and it predicts a respite from the pressure, it may become a safety signal through backward conditioning. Safety signals can be anything: a click! or a special word; a bandana or vest; a location; or a familiar animal or person. Owners often become safety cues for their pets. For example, I was on a recent follow-up consultation for an Australian shepherd that was fearful and aggressive toward visitors in the home. The owners had set up a spacious designated dog area, and in general he seemed content being confined there. During the consultation we wanted to see if the dog would be comfortable in this space when a visitor was present, which would give the owners the “luxury” of finally being able to invite friends to their home. Interestingly, when I was present in the home the dog was comfortable in the designated dog area only when one of the owners stayed with him, and he was distraught when the owner left to join us in an adjacent room. This suggests that the owner, but not the space, had become a conditioned safety signal. The up-side to this story is that when an owner serves as safety signal, it is evidence of a strong trusting relationship between the animal and human. Why all the fuss about safety signals? In addition to their value at inhibiting fear and avoidance, safety cues possess the following properties that make them particularly appealing for behavior modification: 1) Once learned, it is very difficult to retrain the safety signal as a danger signal; 2) Safety signals can ease the effects of environmental and social stressors; 3) Safety cues possess rewarding qualities and seem to act as antidepressants; 4) In the presence of safety signals, animals tend to engage in naturally rewarding behaviors like exploration, eating, and social interactions; in contrast, danger signals inhibit these behaviors and fearful animals do not value food or social attention; 5) Safety signals inhibit new fear conditioning; and 6) The ability of safety cues to inhibit fear and anxiety is generalized across situations. A fascinating discovery is that these properties of safety signals do not apply to people with PTSD, who cannot learn to discriminate between safety and danger cues. This unique impairment can be used to diagnose fears having a traumatic origin; it is not known if the same impaired learning is seen in animals that have a history of trauma, but it would be an important clinical finding. References Christianson, JP, Fernando, ABP, Kazama, AM, Javanovic, T, Ostroff, LE, and Sangha, S. 2012. Inhibition of fear by learned safety signals: A mini symposium review. The Journal of Neuroscience 32: 14118-14124. McGreevy, P, Henshall, C, Starling, M, McLean, A, and Boakes, R. 2014. The importance of safety signals in animal handling and training. Journal of Veterinary Behavior (in press)
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