From these most recent findings and their connection with serotonin, Dodman has a new theory. He thinks that the CDH2 gene, which involves glutamate, is required for a dog to be genetically predisposed to CCD in the first place. A human might have a different predisposition gene, but Dodman guesses it involves glutamate too. Serotonin genes, he thinks, are modifiers that control to what degree a dog has CCD (or a person has OCD). He now hopes that someone will look for similar modifier genes in humans, or expand standard OCD treatment to include both serotonin and glutamate pathways.

Dodman still thinks that any hesitation to accept research based on a dog model of human OCD doesn’t lie in specific doubts about the validity of the model, but in a greater philosophical problem: the difficulty in accepting that our minds might be closer than we want to believe to the minds of dogs.

“It really helps to be a veterinarian,” he says. “Because one of the things people say when you’re a vet is, they say: ‘It must be so difficult because you have to learn all these differences between the various species.’ The answer is, actually you don’t. What you learn to do is appreciate the sameness.”

Understanding obsessions

In her book, Rapoport wrote that she was amazed at the sameness of OCD behaviours. Though she remains unconvinced how much animal models will ultimately help, she did say that psychiatrists could learn from the work of ethologists, who study inborn behaviour patterns in animals. Rapoport’s collie dog turned in circles – not compulsively, but before it lay down to sleep. In the dog’s ancestors, that behaviour was conserved to trample down grass or ward off hiding snakes or insects. But in her suburban home, it remained.

“The highly selective nature of OCD behaviors is just as remarkable,” she wrote. “Washing, grooming, hoarding – any theory of this disease must account for the incredible selectivity of these behaviours, which could be action patterns from an ethologist’s field book. As psychiatrists, we need to be field observers much more often than we are.”

The day after Sputnik, I meet Bella, another bull terrier who used to spin but after treatment has stopped almost completely. Bella’s owner, Linda Rowe-Varone, has a similar tale to Sputnik’s owners: one day her sweet puppy started to spin, and nothing she could do could stop her. Like Dan Schmuck, she tells me she almost reached breaking point.

“There was a time I really thought she was spinning so much that I could not keep her in my home anymore,” she says with tears in her eyes. “And Dr Dodman just kept telling me, ‘Just wait it out, wait it out, you’ve got to give her a little more time.’ And I’m really glad I did.”

Bella is active, playing and running around the examination room. Rowe-Varone tells us that Bella is also obsessed with balls, and she has to limit what kinds of toys she is exposed to. I wonder where the vets draw the line? All dogs have a favourite toy, one they love to play with. When can they call it an obsession? (When did I go from being a person who liked to be clean, to becoming obsessed with cleanliness?) Rowe-Varone says that she has to keep balls hidden in the garage, and if Bella sees them, she will sit outside the garage door for hours.

The debate about whether dogs can truly obsess doesn’t enter this room. The consensus here is that Bella knew her balls were in the garage and couldn’t get them off her mind. I’m struck by how accepting dogs as an animal model for human OCD required two shifts in thinking: not only did we have to become more animal, but we had to grant them a bit more humanity as well.