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A new study by University of New South Whales neuroscientist Michael Valenzuela and colleagues looked at the brains of a variety of breeds with snouts of different lengths. The researchers found that specimens of Canis familiaris with shorter snouts had brains that were rotated forwards by 15 degrees. They also found that the olfactory lobe in the frontal portion of the brain, which is involved in processing smells, has been moved downward.
 

“As a dog’s head or skull shape becomes flatter—more pug-like—the brain rotates forward and the smell center of the brain drifts further down to the lowest position in the skull,” Valenzuela told New Scientist, whose web site published this article about the study. “It’s something that hasn’t been documented in other species.”

The study is the first evidence showing that selective breeding of dogs to create physical characteristics, which has been going on for thousands of years, influences brain organization as well. 

Lisa Collins of the UK’s Royal Veterinary College told New Scientist  that the brain changes may explain why long-snouted dogs are better at scent work, such as searching for drugs and bombs, than short-snouted breeds.

Valenzuela told the Australian newspaper The Age that brain rotation in short-snouted breeds may have been an evolutionary trade-off because the length of their skulls decreased due to selective breeding.

“We speculate that one of the reasons the brain may be rotating in pug-like dogs is that if it hadn’t rotated, then there would be no space for the frontal lobe to develop,” he said.