For several years, scientists have known that many animal species are capable of estimating quantities. This ability is not based on calculation, but on an intuitive system that allows you to quickly assess whether one group is more numerous than another.
In humans as in primates, this faculty is associated with a specific region of the brain, called the parietal cortex. The researchers therefore wanted to know if dogs used a comparable mechanism.
To answer this question, they recruited 11 pet dogs, trained to remain perfectly still during functional magnetic resonance imaging (fMRI) scans. This technique makes it possible to observe the areas of the brain which are activated depending on the tasks performed.
During the experiment, the doggies looked at series of images composed of black dots on a white background. The number of dots varied regularly, but their size and arrangement also changed to prevent the canids from relying on other visual cues, such as surface area or density.
The scientists then compared the brain activity recorded when the quantities remained the same and when they changed. They were also interested in the importance of these variations. Indeed, it is generally easier to distinguish 2 very different quantities than 2 almost identical sets.
An intuitive quantity estimation system
The results of this study* show that the parieto-temporal cortex of dogs clearly reacts to changes in quantity. The greater the difference between the sets presented, the more the activity observed in this region of the brain increases.
As scientists explain, the brain distinguishes 2 quantities more easily when the gap is marked, for example between 4 and 12 elements, than when the numbers are close, such as 8 and 10. This phenomenon corresponds to what researchers already observe in humans, monkeys and several other animal species.
This discovery reinforces the idea that the sense of quantities is an ancient ability during evolution. It would therefore not be specific to primates nor linked to the learning of mathematics, but would constitute a cognitive tool shared by many mammals.
For dogs, this ability can be of practical interest. It could help them quickly compare the sizes of 2 groups of animals, locate a more abundant food source or even evaluate certain social situations without needing to count precisely.
The scientists emphasize, however, that their work does not prove that our faithful companions know how to count in the strict sense that humans understand. The study instead highlights an intuitive system for estimating quantities, present directly in their brain.
* “Canine sense of quantity: evidence for numerical ratio-dependent activation in parietotemporal cortex”, Lauren S. Aulet & al, Biology Letters, December 2019.