Louise’s daughter asked her an interesting question one day while they were walking their dog. The friendly golden retriever had just stopped to say hello to a passing pug. “How does Kiefer know that’s another dog?” the little girl asked.
It’s a good question, especially when you consider the huge physical diversity of different breeds. According to veterinarian Dr. Dominique Autier-Derian of the National Veterinary School in Lyons, France, dog breeds show the largest morphological variety of any animal species, which means visual recognition represents a true cognitive challenge for individual canines.
For example, compare a great Dane, mastiff, Chihuahua and an Irish wolfhound. Given the huge differences between these breeds in size and shape, not to mention coat type, color and muzzle length, they don’t look like they’re even from the same species. Unlike wolves, foxes or other wild canines, domestic dogs present a huge phenotypic diversity. With so much variation in size, shape and appearance, how do dogs know when they’re interacting with other dogs?
In any social interaction, dogs need to first determine whether the other animal belongs to his own species. This can be done by smell, sight and hearing, but it can also involve cognitive processes such as discrimination and categorization. In a recent innovative study, Dr. Autier-Derian found that, using visual cues alone, dogs are able to pick out the faces of other dogs (regardless of breed) from other animal species, and group them into a category of their own.
Nine adult dogs (five females and four males owned by students at the National Veterinary School) took part in this study. Two of the nine dogs were purebred (one a Labrador, one a border collie), and seven were cross breeds. None had the same morphotype in terms of form, color, marking, hair length and ear type, whether upright or drooping. All the dogs were between two and five years of age, had extensive prior experience of visual interspecific and intraspecific interactions, and basic obedience training. They also underwent ophthalmological and behavioral examinations.
How the study worked
Dr. Autier-Derian and her fellow researchers wanted to observe whether the nine dogs could discriminate any breed of dog from other species of animal, including humans, and whether they could group all dogs together, regardless of breed, into a single category.
The dogs were shown 144 pairs of colored digital head pictures depicting various dogs, animals and humans. The images were displayed on a pair of computer screens at the dogs’ own eye level. Each image pair included the face of an unfamiliar dog, and the face of an animal of a different species, including humans. The dog images encompassed many purebreds and mixed breeds and were picked to illustrate the wide variability of canine morphotypes, with different head shapes, hair length, color, and ear positions. The non-dog photos included people as well as 40 different species of both domestic and wild cats, rabbits and birds.
The dogs were trained to sit in front of an experimenter, on a line between the two screens. Upon hearing a command, each dog would make a selection between the two images in front of him by going to one of the screens and putting his paw in front of the chosen image.
All nine dogs in the study were able to group all the dog images, regardless of breed, into into a single category despite the diversity of breeds.
“Dogs display a very efficient visual communication system toward conspecifics [same species], and also to human beings,” she says.
“The fact that they are able to recognize their own species visually, and that they have great olfactory discriminative capacities, ensures that social behavior and mating between different breeds is still potentially possible. Although humans have stretched the canis familiaris species to its morphological limits, its biological entity has been preserved.”
We already know that dogs are smarter than most people think, but this study demonstrates they’re even more intelligent when it comes to knowing how to recognize their own species, whether it’s a toy poodle or a great Pyrenees.