6 min read


Can Dogs Smell Better Than Humans?



6 min read


Can Dogs Smell Better Than Humans?


We think of our dogs as having a sense of smell that is far superior to ours. We rely on dogs to detect scents for us in service to our needs in the military, police work, field work, pest detection and assisting persons with handicapping conditions. Recently, scientists revealed that humans have a better sense of smell than we previously understood.  

We may have different noses and olfactory organs but we both have a very good sense of smell. This surprising news that humans have strong scent detection abilities may give us all pause to appreciate our understanding of our own abilities and the relationship we have with our amazing dogs.


Signs a Dog Has Found a Scent

Handlers of dogs who are working on scent detection must spend time learning their dog's behavior when on and off the trail of the odor. It takes a lot of patience to develop your skills to be effective in interpreting the dog's behavior. 

Experts in the area of scent detection training alert handlers to pay special attention to the dog's search pattern, nose, and the timing of and direction of the dog's nose. Dogs will vary in their sensitivity to scents, depending on the breed, quality of training, and experience with the target odor. The well-trained team is one in which the dog has been trained to sit down or paw at the odor target site. Other dogs may not be as clear in their signaling and the handler will need to be a more astute observer of dog behaviors.

Experts recommend observing the dog's chain of behaviors when searching for the odor target. One sign is an indication the dog is on to a scent. If there are two or more signs, the handler may have more certainty the dog has located the target. 

The "Head Turn" is when the dog stops suddenly and turns the head as if someone pulled the nose in a new direction. There is the "Detailing Sniff" in which the dog has the nose close to the target area and sniffing intently. The "Odor Exhale" is another sign the dog has found a smell.  Some dogs will exhale very loudly when they locate the odor source.

Just as there are signs the dog is on the path to locating the target odor, there are also signs your dog is not tracking. The "Frozen Nose" is when the dog stops and holds the nose above the ground. This happens when the dog has detected the scent of a critter or perhaps the urine of another dog. The dog just found something that is interesting to the dog. 

The "Instant Alert" occurs when the dog stops and signals but the animal is nowhere near the target odor. When this occurs, this usually means the dog is confused. The "Wandering Sniffer" is the dog that goes back and forth, as if on a trail. 

The handler needs to observe if the dog is moving to the target or just engaged in a search pattern that is going nowhere. It usually only takes about 20 seconds to determine if the dog is onto a scent or just exploring. The human's behavior will play a role in the dog's scent detection ability. Humans can be signaling as well with subtle indications such as eye gaze, leash tightness and where the human stops to stand.

Body Language

If you are wondering if your dog has found a scent, watch for the following:

  • Sniffing
  • Body Freezing
  • Head Turning
  • Stiff Tail

Other Signs

Other signs that a dog is smelling something include:

  • Stopping To Sniff The Ground
  • Wandering Back And Forth
  • Displaying Trained Behavior Once They Have Found The Source

The History of Dogs' Smelling Power


Scientists report that dogs' olfactory senses are 10,000 to 100,000 times stronger than the sense of smell for humans. The olfactory system of the dog is their most powerful organ for taking in and understanding their world. 

Begin by thinking about the dog's nose. The wetness of the nose is due to a mucus that helps them capture smells. They will lick their noses to make them wet to help their ability to smell. The dog breeds with the longest noses, the hounds, are best suited for search and detection tasks - partially because their longer noses help them to take in more scent. They were bred to be the most powerful sniffers. 

Now, let us consider when the dog takes in a whiff of air. When a dog inhales, the air particles travel two distinct pathways. Some of the particles travel to the lungs, while the other particles flow into the olfactory area of the dog's nose. 

The dog has 300 million olfactory receptors in their noses. Humans have 3 million receptors. The proportion of the dog's brain dedicated to smell is 40 times greater than that of humans. Dogs can also wiggle each nostril independently which helps them to detect the direction and source of a smell. 

Located in the back of the dog's mouth at the nasal cavity, is a second olfactory system that is called Jacobson's organ. This secondary organ picks up pheromones or the odor of hormones that indicate a readiness for mating. The sense of smell is linked to the primitive areas of the brain. The dog's sense of smell is stronger than the sense of sight, which makes scent critical for their survival.

Science of Dogs Smelling Better than Humans


While the human's sense of smell is not as powerful as that of the dog and other animals, the human's sense of smell is known to be accurate. The human nose has two small odor-detecting patches located high up in the nose. 

The human nose can actually detect certain substances in dilutions of less than one part in several billion parts of air. The human nose is also the main organ for detecting taste. Our tongues can detect 4 tastes - sweet, sour, salt, and bitter. All other tastes are detected by the nose. The human sense of smell is developed by the age of 8 years and can decline in old age. Humans can also be trained to detect scents. 

A recent study on the scent detection of humans demonstrated that humans can be accurate. A research team led by Jess Porter and Noam Sobel at the University of California, Berkeley demonstrated human scent-tracking abilities with chocolate. They dipped 10 meters of twine in chocolate that was distributed in an open field. 

Thirty-two undergraduates were blindfolded and wore thick rubber gloves and knee pads to prevent them from using other sensory cues. Two-thirds of them were accurate on the scent of chocolate. The students reported that it was challenging. A few of them were able to improve their performance with practice. 

The researchers learned that the sniff strategies used by the students included comparing the odor intensity between subsequent sniffs and comparing the odor intensity at the two nostrils during single sniffs. If we had to get on all fours to track scents, we have the capacity to track scents and improve. Some of us just might be willing to do anything for chocolate!

A neuroscientist, John McGann, of Rutgers University-New Brunswick, conducted a meta-analysis of studies on human and dog sense of smell. The olfactory bulb in the human brain is larger than thought in past studies. Humans have an accurate sense of smell. It is proposed that, because of adaptation, humans do not rely as heavily on their noses as other species. This scientist believes that humans are as good as dogs, but not the same. It has been posited that it is still an open ended question as to whether dogs have a better sense of smell than humans. 

Training Your Dog with Scent


Dogs are born with a fully developed sense of smell. It can be fun to work with your dog to play scent games. When you have fun with your dog with these games, you are also practicing skills that will make your dog better at scent detection. 

Find the Food: Start by placing one or two pieces of food in an open area when the dog is out of the room. The dog will find it when they re-enter. Then, hide pieces of food in various places. The dog will learn to look for a reward.

Pick the Hand: Begin by having your dog sniff your hand. Then, place a small bite of a treat into a palm, and holding your palms down, say "Find it". When the dog locates it, then turn the hand up and give the dog the treat saying "Good, find it". Make sure the dog's nose is clearly pointed to the hand with the treat before the reward. This game is teaching the dog that location can vary and the dog must locate it by scent.

Shell Game: It is like the "Pick the Hand" game but instead of the hand, you will be placing the treat under objects. The same as in the shell game, the treat is placed under a cup and the cups are moved about. The dog must find the cup with the scent to get the treat. 

Scent Trails: Take a favorite toy, like a ball, and saturate it with a scent. It does not have to be a food scent. It can be any non-toxic smell. Play with your dog with the scented toy and follow the activity with a reward. Then, hide the toy. Take small pieces of paper with the scent and place them about the house, as a trail. Reward the dog when the trail is followed to the scented toy. Gradually reduce the trail until the dog is able to search and find the scented toy.

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Safety Tips if Your Dog is Bothered by a Scent:

  1. Sprinkle baking soda on the carpet, floors, and furniture and let it sit overnight, then vacuum it up.
  2. Wash whatever you can in the washing machine with a mixture of oxy-powered laundry detergent and a ¼ cup of apple cider vinegar.
  3. Use a carpet cleaning machine and products with non-toxic shampoos.
  4. Avoid air fresheners that can be toxic to animals.
  5. Your pH balance is different from your dog's - do not use human shampoos on your dog.

By a Cavalier King Charles Spaniel lover Pat Drake

Published: 04/03/2018, edited: 04/06/2020

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