The placebo effect is traditionally thought to require some sort of conscious awareness. The sugar pill you just took helps your headache only because you think it will work. Recent research with rats challenged that assumption, and now it looks like placebos can fool dogs too.

Despite the fact that placebos can involve both physiological and psychological changes, it's usually thought of as being driven by social factors, often involving authoritative, trustworthy people providing specific information. "This pill will make you sleepy," for example. But it can also be far simpler.

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It turns out that the placebo effect can be triggered by the simplest form of learning there is, universally effective across the animal kingdom: classical conditioning.

The idea is simple: the animal (or person) makes an association between an active substance, like a medication, and some neutral stimulus. In the case of a "conditioned placebo" effect, that could be the smell, taste, or color of the substance, or some environmental cue having to do with the treatment process itself, such as the place where it is administered. After the treatment is administered several times, the procedure can be offered without the active ingredient. If it still results in the same physiological or behavioral effects, then a placebo effect has been induced.

A Perfect Platform

Because domestic dogs are so uniquely tuned to human social cognitive cues and bond so intimately with their owners, they're also susceptible to separation anxiety. In simplest terms, that's a fear or dislike of isolation, even in familiar spaces. The pharmacological aspect of treatment for severe anxiety in dogs typically involves a drug called Sedalin, which is a tranquilizer. It acts as a depressant, resulting in both neurobiological and behavioral changes.

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That provided Hungarian ethologists Zsófia Sümegi, Márta Gácsi, and József Topál with the perfect platform to find the placebo effect, if it exists in dogs. They weren't necessarily asking whether using a placebo effect was a useful treatment for separation anxiety; instead, they used separation anxiety as a means to see whether dogs are susceptible to the placebo effect.

So they rounded up 28 dogs whose owners reported severe separation anxiety. To avoid any potential confounds, they ruled out dogs who were already taking medications or who had any known health problems. While the owners all provided informed consent, they were not told whether their dogs would be receiving the Sedalin or a vitamin instead.

To measure the dogs' anxiety, the researchers used a form of the "strange situation." It started out as an experiment designed by psychologist Mary Ainsworth to assess the quality of human parent-child relationships. That's not as crazy an idea as it might seem; the dog-owner relationship has often been compared to the parent-child relationship, after all.

The modified dog version of the strange situation had four stages: first the dog was introduced to a new room with its owner. Then the dog was left alone. After two minutes, a stranger entered the room and attempted to interact with the dog. Then the stranger left, and the owner returned. It's all a bit contrived, but assessments of a dog's behavior in each of these situations reveals important information about how stressful it is to be separated from its owner.

After establishing the baseline, each dog had three conditioning trials, all on different days. Half the dogs were given a dose of Sedalin hidden in a piece of liverwurst before each trial, and the others were given a vitamin inside a piece of liverwurst. All the dogs were also given a spray of water on their muzzles and paws. The water spritz was meant to ritualize the procedure.

During the conditioning trials, the owners never left the room. The idea was that the researchers wanted to create an association between the dogs' relaxed feelings and the testing room, rather than between the medication and the owner's disappearance. As expected, the dogs given the medication were more relaxed in general, including when the owner left the room, than were the dogs given a vitamin.

Photo by Javier Brosch via Shutterstock.com

Then, on a final day, came the test trial. This time, all the dogs received the vitamin. Consistent with the placebo effect, those dogs who had previously received the Sedalin still showed the same relaxed behaviors, despite not being administered the drug itself. The dogs' behavior during the test trial depended on whether they'd been given sedatives during the prior trials.

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Sümegi and her team verified that the placebo effect was not limited to humans or laboratory animals, but is probably more widespread in the animal kingdom. It doesn't require consciousness or overt verbal instructions; all that is necessary seems to be the ability to learn.

Ritual Matters

By highlighting the environmental and procedural aspects of the drug administration, rather than explicitly linking the medication with owner separation, the researchers very cleverly assured their own success. The focus was on the dogs' inner psychological state, rather than on the separation itself. "During the conditioning trials dogs had the opportunity to learn about the 'relaxed nature' of the environment," writes Sümegi, "but they had no opportunity to learn how to cope with separation distress under the influence of Sedalin." It's therefore striking how well the dogs learned to cope as the experiment wore on. In other words, they learned to associate their own relaxed feeling with either the ritualized procedure (liverwurst and water spritzing), or with the testing room, or both. That allowed them to remain calm when separated from their owners.

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While the experiment was intended to probe the nature of the placebo effect, the findings still have practical applications. Dogs with severe separation anxiety are often given medication or behavioral therapy. These therapeutic interventions can be costly, and there are welfare considerations involved in continually treating dogs with anti-anxiety medications. To that end, this finding also has important veterinary implications.

It also underscores the importance of the administration procedure itself. "Our results suggest that by applying a specific regimen, that is, administrating the medicine always with the same environmental cues, for example with the same specific food type and with a set ritual," the researchers write, "the real medicine can later be effectively replaced by placebo." Not only would that save the owner the cost of the medication, for some dogs at least, but it also avoids the need to continually medicate dogs. They add that more research will be necessary to determine what procedural elements are most effective in inducing the placebo effect in dogs.

[Applied Animal Behaviour Science]

Header image: Public domain/Pixabay.