In most social interactions, an animal has to determine whether the other animal belongs to its own species. This perception may be visual and may involve several cognitive processes such as discrimination and categorization. Perceptual categorization is likely to be involved in species characterized by a great phenotypic diversity. As a consequence of intensive artificial selection, domestic dogs, Canis familiaris, present the largest phenotypic diversity among domestic mammals.
The goal of our study was to determine whether dogs can discriminate any type of dog from other species and can group all dogs whatever their phenotypes within the same category.
9 pet dogs were successfully trained through instrumental conditioning using a clicker and food rewards to choose a rewarded image, S+, out of two images displayed on computer screens.
The generalization step consisted in the presentation of a large sample of paired images of heads of dogs from different breeds and cross-breeds with those of other mammal species, included humans. A reversal phase followed the generalization step. Each of the 9 subjects was able to group all the images of dogs within the same category.
Thus, the dogs have the capacity of species discrimination despite their great phenotypic variability, based only on visual images of heads.
[Keywords: species discrimination, categorization, 2D images, dogs]
[They are all good dogs, just some are a bit sharper than others:]
…Progression across the tasks differed between individual dogs (Figure 5). One dog (“Vodka”) presented an extreme pattern. This dog took more time for the learning Task 0 (with 29 sessions), but then, it succeeded rapidly with all of the following tasks, needing only 5 sessions for Tasks 1 and 2, and after that, no more than 3 sessions for each task. This dog needed fewer and fewer sessions to meet the criterion for the subsequent tasks. Ultimately, this dog was among those which needed the lowest number of generalization sessions (ie. 12 sessions = 144 trials). On the contrary, “Bounty” needed increasing numbers of sessions to reach the criterion for the later tasks, with a peak at 39 sessions for the final generalization Task 10. Bounty was among those needing the greatest number of generalization sessions (ie. 56 sessions = 672 trials).
…Thus, our study may suggest that dogs can form a visual category of “dog pattern”…It may be that ultimately it was only in Task 5 that the subjects understood the “dog categorization” required by the experimenter. The “dog category” is an insight which has been especially explored in various species. For human babies, cats are treated as a kind of dog, but dogs are not treated as a kind of cat ( et al 1994; 1996). Experiments conducted on humans and pigeons confronted by pictures of dogs and cats showed that pigeons and humans do not form categories using the same features (Ghosh et al 200420ya; Goto et al 201113ya). We assume that such differences may exist between dogs and humans, and further investigations are needed to support the idea and the nature of “a dog species pattern” in dogs as 1979 suggested with the oak leaf pattern for pigeons. According to the 5 levels of categorization of 1990, from simple discrimination based on perceptual cues to categorization based on complex concepts, we cannot conclude more than that dogs based on their categorization of dog faces on perceptual cues.