Dogs pick out faces of other dogs, irrespective of breeds, among human and other domestic and wild animal faces and can group them into a category of their own. They do that using visual cues alone, according to new research by Dr. Dominique Autier-Dérian from the LEEC and National Veterinary School in Lyon in France and colleagues. Their work, the first to test dogs' ability to discriminate between species and form a "dog" category in spite of the huge variability within the dog species, is published online in Springer's journal Animal Cognition.

Individuals from the same species get together for social life. These gatherings require recognition of similarities between individuals who belong to the same species and to a certain group. Research to date has shown that in some species, individuals recognize more easily, or are more attracted by images of, individuals belonging to their own species than those belonging to another species.

Autier-Derian and team studied this phenomenon among domestic dogs, which have the largest morphological variety among all animal species. Indeed, more than 400 pure breeds of dogs have been registered. The authors explored whether this large morphological diversity presented a cognitive challenge to dogs trying to recognize their species, when confronted with other species, using visual cues alone.

On a computer screen, the researchers showed nine pet dogs pictures of faces from various dog breeds and cross-breeds, and simultaneously faces of other animal species, including human faces. They exposed the dogs to diverse stimuli: images of dog faces; images of non-dog species from 40 different species, including domestic and wild animals; and humans. Overall, the dogs were shown more than 144 pairs of pictures to select from. The authors observed whether the nine dogs could discriminate any type of dog from other species, and could group all dogs together, whatever their breed, into a single category.

The results suggest that dogs can form a visual category of dog faces and group pictures of very different dogs into a single category, despite the diversity in dog breeds. Indeed, all nine dogs were able to group all the images of dogs within the same category.

The authors conclude: "The fact that dogs are able to recognize their own species visually, and that they have great olfactory discriminative capacities, insures 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."

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Reference

Autier-Dérian D et al (2013). Visual discrimination of species in dogs. Animal Cognition; DOI 10.1007/s10071-013-0600-8

The full-text article is available to journalists on request. Illustrations of the experiment are also available.