Dogs use a similar part of their brain as humans to process numbers, they don't need to be trained for this, shows study
Dogs use a similar part of their brains to process numbers of objects as humans do, and they do not need to be trained to do it. The findings of a new study by Emory University shows that dogs spontaneously process basic numerical quantities, using a distinct part of their brains for the task that corresponds closely to “number-responsive neural regions” in humans.
The results, according to Gregory Berns, Emory professor of psychology and senior author of the study, suggests a common neural mechanism deeply conserved across evolution. Berns is the founder of the Dog Project, which is researching evolutionary questions surrounding dogs. The project was the first to train dogs to voluntarily enter an functional magnetic resonance imaging (fMRI) scanner and remain motionless during scanning, without restraint or sedation.
According to the study’s co-author Stella Lourenco, an associate professor of psychology at Emory, understanding neural mechanisms -- both in humans and across species -- gives insights into both how humans rains evolved and how they function now. Such insights, says Lourenco, could lead to practical applications such as treating brain abnormalities and improving artificial intelligence systems, one day.
Unlike dogs and other animals, humans can build on basic numerosity -- which refers to basic sensitivity to numerical information -- in order to do more complex math, drawing primarily on the prefrontal cortex. "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. I'm interested in learning how we evolved that higher math ability and how these skills develop over time in individuals, starting with basic numerosity in infancy,” says the first author of the study Lauren Aulet, a Ph.D. candidate in Lourenco's lab.
For the study, the research team used fMRI to scan dogs' brains. Eleven dogs of varying breeds were involved in the fMRI experiments. The dogs did not receive any training in number tasks. After entering the fMRI, the dogs passively viewed dot arrays -- flashed on a screen -- that varied in numerical value. The results showed that the dogs' parietotemporal cortex responded to differences in the number of dots.
“Eight of the 11 dogs showed greater activation in the parietotemporal cortex when the ratio between alternating dot arrays was more dissimilar than when the numerical values were constant,” says the study published in Biology Letters.
The researchers held the total area of the dots constant, demonstrating that it was the number of the dots, not the size, that generated the response. This, says the team, shows that dogs use a similar part of their brain as humans to process basic quantities, and do not need to be trained to do the task. “Humans and dogs are separated by 80 million years of evolution. Our results provide some of the strongest evidence yet that numerosity is a shared neural mechanism that goes back at least that far," says Berns.
According to the research team, the approximate number system supports the ability to rapidly estimate a quantity of objects in a scene, such as the amount of food available for foraging, or the number of predators approaching. Evidence suggests that humans primarily draw on their parietal cortex for this ability, which is present even in infancy, they add. The ability to estimate quantities of objects in a scene is widespread in the animal kingdom, precious research suggests.
"This basic sensitivity to numerical information does not rely on “symbolic thought or training” and appears to be widespread throughout the animal kingdom," says the study. Much of the research in non-humans, however, has involved intensive training of the subjects, say researchers.
Previous research, for example, has found that particular neurons in the parietal cortex of monkeys are attuned to numerical values. However, such studies, says the team, did not clarify whether numerosity is a spontaneous system in non-human primates because the subjects underwent many trials and were rewarded for selecting scenes with greater numbers of dots in preparation for the experiments.
"We went right to the source, observing the dogs' brains, to get a direct understanding of what their neurons were doing when the dogs viewed varying quantities of dots. That allowed us to bypass the weaknesses of previous behavioral studies of dogs and some other species," says Aulet.