When it comes to testing Fido's IQ, science is saying that size might actually matter. According to to a new study published in the journal Animal Cognition, larger dog breeds outperformed their smaller counterparts in several tests of cognitive intelligence. Led by the University of Arizona, the study examined data from 7,000 purebred dogs from across 74 different breeds, alongside user data from the site, dognition.com, which allows dog-owners to test their dog's cognitive abilities through a variety of activities and submit results for research.
After accounting for any previous canine training, researchers found that larger sized dogs did better overall than smaller ones in the areas of short-term memory (finding a hidden treat after various waiting periods) and self-control (refraining from eating a treat per owner's orders even when owner left the room). However, when tested for other types of intelligence, like social intelligence (response to certain human gestures), neither larger nor smaller breeds appeared to outperform the other.
While there have been previous studies on brain size and related signs of intelligence, this particular study was especially notable because of the wide variation in brain sizes among dogs. "Previous studies have been composed mostly or entirely of primates, so we weren't sure whether the result was an artifact of unique aspects of primate brain evolution," said Daniel Horschler, a UA anthropology doctoral student, member of the UA's Arizona Canine Cognition Center, and study author. "We think dogs are a really great test case for this because there's huge variation in brain size, to a degree you don't see in pretty much any other terrestrial mammals. You have chihuahuas versus Great Danes and everything in between."
As for the exact reason why brain sized affected certain cognitive functions? Horschler says there’s still more studying to be done. "We think of it as probably a proxy for something else going on, whether it's the number of neurons that matters or differences in connectivity between neurons. Nobody's really sure yet, but we're interested in figuring out what those deeper things are."
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