Male dogs are from Mars, female dogs are from … Pluto?
True, dogs aren't exactly a fertile market for self-help manuals. But a new study finds that the brains of male and female canines are not the same -- and in at least one task, the females have an edge.
The researchers aren't sure of the root cause of these doggie brain differences, but the study points to the need to take sex into account when trying to understand how animals think.
"When you start looking, you get some very interesting and instructive results," study researcher Corsin Müller, a cognitive biologist at the University of Vienna, told LiveScience.
Peering into the canine mind
Müller and his colleagues tested female and male dogs -- "completely normal family dogs," Muller said -- to see whether they understand a concept called "object permanence," which is the realization that objects don't disappear and don't change form just because they go out of sight. Children learn this physical law around the age of 1 or so. The question, Müller said, was whether dogs understand it too. [Read: 10 Things You Didn't Know About the Brain]
The researchers set up a wooden board and a system of blue tennis balls attached to strings. The dogs, 25 female and 25 male, watched one of four scenarios: A small ball disappearing behind the board and re-emerging; a large ball disappearing and re-emerging; a large ball disappearing and a small ball emerging; or a small ball disappearing and a large ball emerging. The first two experiments were the "expected" conditions, which didn't break any laws of nature. The second two events, in which a ball would seem to shrink or grow while out of sight, were the "unexpected" or impossible conditions.
The researchers measured the dogs' ability to understand that something impossible had just happened by measuring how long they stared at the emerging ball. The experiments are similar to those used to understand infant cognition.
"If something unexpected or, say, impossible is to happen, children and animals will look longer at the event," Müller said.
At first glance, dogs did seem to look longer at the event when the ball seemed to mysteriously shrink or grow. But when the researchers broke the results down by dogs' sex, they found that male dogs hadn't noticed anything odd at all. Female dogs, on the other hand, stared at the "unexpected" conditions for more than 30 seconds on average, more than three times longer than the 10 seconds or so they spent looking at the balls when they didn't change size.
The sex difference emerged across breeds, which ranged from large to small, purebred to mixed, Müller said.
There are three possible explanations for why male and female dogs -- or any animal -- might show sex-based brain differences. The first is that evolutionary pressures in the past might have subtly shifted male and female brains. If one sex hunts while the other builds nests, for example, the nest-builder might gradually become better at spatial reasoning, while the hunter might evolve to be better at navigating through unfamiliar territory. Another possibility is that brain differences arise because of childbearing duties; a female solely responsible for rearing her offspring might show greater nurturing skills than a male that has little to do with his offspring after mating.
Neither of these is a good explanation for dogs because their sex-specific differences seem very limited, Müller wrote. Instead, he suspects a third possibility: That the sex differences in the brain are a side effect of other biological sex differences.
"[Most likely,] this is just a byproduct of sex hormones working on the brain, without necessarily having a function," Müller said.
Although this experiment gave female dogs the cognitive edge, Müller said it's likely that future findings of sex differences would even the intelligence scale.
In humans, Müller said, "there's tons of differences you can find, but for everything where you find men are better than women, you can find something where women are better than men."
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.