The Real Reason Dogs Stick Their Heads Out Of Car Windows
Though there will never be a consensus as to whether dogs are better than cats (nor could or should there be; both are great), canine and feline lovers alike would tend to agree on one thing: dogs are often regarded as freer and sillier than cats.
Our feline friends can seem to have an aloof, almost judgmental approach to the humans they share their lives with, but this often isn't a life dogs want any part of. They'll erupt into 15-minute sessions of "the zoomies" for no reason at all, happily play in muddy puddles on walks, and thrust their heads out of the open windows of cars seemingly for the pure, unbridled, and uninhibited joy of life.
The latter behavior, as anyone who's experienced the unpleasantness of heavy winds blowing in their faces will tell you, appears rather strange. However, it seems that dogs do this so that they can enjoy more of the greatest canine pastime of all: Sniffing absolutely everything.
A dog has an incredible sense of smell
According to PBS' Nova, a dog's nose is far, far more sensitive than a human's. James Walker, once the director of Florida State University's Sensory Research Institute, states that the ability of dogs to smell "10,000 times better" is a modest estimate, and a study Walker contributed to suggests that a dog's sense of smell may be 100,000 times more acurate.
As such, it's difficult to imagine the sensory extravaganza dogs experience during their regularly-scheduled sniff stops on walks. It's exactly the excitement they're seeking, though, it seems, when they seat themselves in the car with their heads out of the window, tongues blowing freely in the breeze.
Per Live Science, the science of smell is quite complicated. The olfactory membrane in the nose (of dogs and humans alike) reacts to air and molecules of smells. Receptors in this area, which are the size of a postage stamp in humans, react to the particles of odor and send them to the olfactory bulb in our heads. This is how smells are both detected and identified, from a total of about 10,000 that humans can discern. Dogs, needless to say, are far more smell sensitive, hence their eager post at the car window.
Air flows and the nose knows
Mental Floss states that, as it is airflow that permits the detection of different scents, more airflow equals more odors. This is the kind of math that our faithful dogs can get behind, and so it's believed that sticking their heads out of car windows with their mouths open gets them access to hitherto-unimagined levels of smell nirvana. Throw in the fact that the car is surely moving much of the time and so new smells are coming and going all the time, and it's easy to see the appeal of this practice. If you're a dog, that is.
The olfactory membrane of a dog is much larger than ours, Mental Floss goes on. It's around the size of a handkerchief, reportedly, and contains 225 million scent receptors to our meager 5 million. Getting the air flowing around that big sniffer is surely a treat.
A dog's sense of smell is truly remarkable. Per VCA Animal Hospitals, they can detect the adrenaline in humans and can manipulate their nostrils separately to determine the location of a smell (which does wonders for their sense of direction). They even have a unique organ, Jacobsen's organ, in their nasal cavities, which allows for the detection of various chemicals such as pheromones. In short, dogs are meant to sniff their way through life, which seems to be exactly what they're trying to do when they're out for a drive.