The answer lays with psychology, human psychology. I found this remarkable quote in an Nature article that gives us the clue.
“Dogs are the only naturally occurring models of psychiatric [anxiety-]disorders.”
During human evolution two kinds of animals were domesticated.
- Animal that grow resources, meet, milk, eggs, fleece, and feathers in particular.
- Animals that are exploited, that have to take on daunting tasks.
In human culture, the former group is considered inferior so you can easily kill them, fleece them, and steal their eggs. The human culture needs this perspective of inferiority to not feel guilt when eating their meat for instance.
The other group of animals is rarely eaten. Though there exist some cultures that eat horse beef, in central Asia for instance, this habit is rather uncommon in Western culture. Also the exploitation animals are mostly flight animals. That is a horse is forced to plow by a whip and a dog into obedience by punishment. Dogs can fast learn to avoid punishment by simply complying to threats and commands (that are conditioned threats). Therefore we call dogs intelligent.
Donkeys are an exception they are not a flight animals. They cannot be taught by a whip. Therefore they are considered stupid.
Dogs, on the contrary, during their domestication were made even more fearful. According to the ruling opinion breeders believed they made them more intelligent, they made them more compliant though.
Similar to dogs humans were domesticated. By the rulers of all ages the breeding of the most fearful variety of humans was favored. It was not a question of intelligence. On the contrary, those more fearful humans showed even less creativity, but nevertheless they were easier to force into obedience.
In summary dogs and humans share the same burden of domestication which results in the same anxiety disorders, and as the publication says the same drugs seem to help . Dogs are therefore an excellent model organism to test antidepressants (the article claims), and for dictators dogs are the perfect role model to train their skills of oppression.
1. Cyranoski D. Genetics: Pet project. Nature News. 2010;466(7310):1036-1038. doi:10.1038/4661036a.