Dogs image via Shutterstock

Dogs seem to stick their heads out of moving cars almost any chance they get. What’s so great about a wind-whipped snout?

While I wasn’t able to find any scientific research on the phenomenon, a number of dog behaviorists agree that the window’s main draw isn’t the scenery or the breeze. What dogs are after are smells.

A few months ago, in a post about bloodhounds, I explained that dogs are basically walking noses. While our human olfactory membranes (a lump of tissue tucked up in the nose) are only about the size of a postage stamp and hold some 5 million olfactory receptors, or “scent cells,” a large dog has an olfactory membrane closer in size to a handkerchief and more than 225 million receptors.

As air moves over the olfactory membrane, odor molecules settle on the scent receptors and get recognized. The more air there is flowing over the membrane, the more scents the dogs can detect. So when a dog sticks its head out the window, it’s like pigging out at a hi-definition all-you-can-smell scent buffet.