It's a familiar sight - a car cruising along the road with a dog's head sticking out of the open window, mouth agape like some sort of canine grin and ears flapping wildly in the breeze.
Any dog owning motorist will know that as soon as a window goes down their pooch will most likely thrust its snout right out of it.
But just why do dogs do this?
Although to date there has still not been an in-depth scientific study into the subject many dog behaviourists think they have the answer to the mystery.
Dog experts believe the reason dogs stick their heads out of car windows is to sniff the air.
Canine noses are many more times more sensitive than those of humans with some larger dogs having more than 40 times more smell sensors than we do.
As air moves across a dog's smell sensors it can detect different odours and the faster the the air moves the more odours the dog can detect.
Experts believe by sticking their heads out of a moving car dogs are indulging themselves in a glorious smelling binge.
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