Canine companions are capable of processing numerical information using a similar part of their brains as their human counterparts, new research suggests.
When faced with numerical data, brain scans indicate that the parietotemporal cortex activates in both dogs and humans. The similarity between the two species suggests that common neural mechanisms for counting have been retained throughout the evolution of mammals, write Emory University researchers in the journal Biology Letters.
In human and non-human primates, the parietal cortex is most commonly linked to spatial cognition, multisensory integration, and attention. The intraparietal sulcus, a subregion of the parietal cortex, is the primary locus of numerical processing, while the temporal cortex is most commonly associated with object recognition and auditory/language processing, study author Lauren Aulet explained to IFLScience. In dogs, far less is known about the functions of these brain regions.
"Our work not only shows that dogs use a similar part of their brain to process numbers of objects as humans do – it shows that they don't need to be trained to do it," said Gregory Berns, professor of psychology and senior author of the study, in a statement. Berns is the founder of The Dog Project, an organization that became the first to train dogs to enter functional magnetic resonance imaging (fMRI) scanners and remain motionless without restraint or sedation.
To come to their conclusions, researchers placed 11 specially trained dogs of varying breeds in fMRI machines. None of the dogs received training in numerosity, or the concept of quantifying objects. These dogs were then shown differing numbers of dots on a flashing screen, the size of which were kept consistent. Eight of the dogs showed greater activation in the parietotemporal cortex, presenting some of the “strongest evidence yet that numerosity is a shared neural mechanism” dating back millions of years.
"In dogs, we found that the parietotemporal cortex responded to the differences in the number of items shown on the screen, suggesting that dogs, like humans, have the ability to perceive numerosity. We believe this evidence suggests that the ability to perceive numerosity has been conserved over evolution, perhaps playing a role in avoiding predators or foraging for food," said Aulet.
Research shows that humans in Eurasia began to domesticate wolves sometime between 10,000 and 40,000 years ago, and the dynamic human-dog duo has continued to evolve alongside each other ever since. Studies suggest dogs have evolved to mimic human facial expressions and may even share unique learning abilities with their human best friends.
"Understanding neural mechanisms – both in humans and across species – gives us insights into both how our brains evolved over time and how they function now," said co-author Stella Lourenco, an associate professor of psychology at Emory.
The concept of numerosity does not rely on symbolic thought or training and is widespread throughout the kingdom. Wild baboons have been shown to make decisions based on numerical data in much the same way as humans do. A 2018 New York Times feature described the many animals that have evolved a “keen sense of quantity”, from orb-weaving spiders and small fish to the male túngara frog of Central America. In the animal kingdom, numerosity may be used to estimate objects in a particular scene, such as the number of predators or the amount of food. But humans build on the concept of numerosity to make it applicable to the immediate world around them and beyond.
"Part of the reason that we are able to do calculus and algebra is because we have this fundamental ability for numerosity that we share with other animals," said Aulet, who added she is interested in learning how humans evolved higher cognitive abilities and how these skills develop over time in individuals.
Understanding numerosity across species could someday help inform how to treat brain abnormalities or improve artificial intelligence systems, the researchers conclude.