A dog's sense of smell is a marvel of biology, thousands of times more sensitive than what any human nose could muster. And one scent that sticks the strongest in a dog's mind, according to researchers from Emory University in Atlanta, is the whiff of a familiar human.
Twelve dogs, trained to sit still in an MRI scanner, sniffed swabs from human armpits and canine nether regions. Of the different scents -- including a strange dog's aroma and the dog's own odor -- the smell of a familiar human sparked the most neural activity. And in every dog, the area that lit up the brightest on the MRI scans was the same part of the brain that processes rewards like food and play.
"While we might expect that dogs should be highly tuned to the smell of other dogs, it seems that the ‘reward response' is reserved for their humans," says Gregory Berns, a biologist whose team published this research in the journal Behavioural Processes. Berns hopes to use these brain-imaging techniques to shed light on which dogs make the best companion animals.