How long a dog can remember its owner's smell?

How long a dog can remember its owner's smell?

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Can dog remember multiple smells? and how long it can remember a smell?

The Amazing Science Behind Pets That Find Their Way Home

A pity you can’t ask a dog for the shortest route home when you’re lost&mdashor a cat or a seabird or a tortoise or a dung beetle, for that matter. Because if you could ask any of them how to get pretty much anywhere, odds are they’d know a lot more than you think.

Animal navigation has long been something of a black box for scientists. The mystery of how nonhumans&mdashwithout benefit of maps, language or GPS&mdashmanage to find their way from place to place, often over very great distances, presented itself anew recently when a dog walked 11 miles from its new home to return to a former foster owner. The feat was especially remarkable because the dog had been taken to its new location by car and had to find its way back on foot&mdashmeaning it hadn’t had a chance to learn the route. Even more impressive was the 2013 tale of the geolocating cat that had been lost and found its way home after a journey of two months and 200 miles. So how do animals manage such prodigious&mdashand precise&mdashfeats of travel?

The kind of natural map any animal follows depends largely on the species. As TIME has reported, seabirds are believed to steer mostly by the sun and the stars, since if the animals are ever going to get lost, it tends to happen when the skies are overcast. The same is true of the unglamorous dung beetle. While naturalists have not extensively tracked the species’ perambulations in the wild, they’ve studied them in&mdashyes&mdashplanetariums. As long as the artificial Milky Way was in view, the beetle and its dung ball rolled right along. Throw the switch and change the stars, however, and the little critter was completely flummoxed.

Many more animals navigate via magnetism&mdashorienting themselves along the north-south lines of Earth’s magnetic fields. In one study of baby sea sea turtles, which typically migrate east after hatching, changing the orientation of magnetic generators around a swimming pool changed the direction in which the hatchlings swam too. Pigeons were thought to navigate the same way, especially since they have cells in their beaks that are heavy in iron. Later studies, however, found that those cells were related to the immune system, not navigation.

Mammals&mdashand particularly two of the species of mammals that humans love best: dogs and cats&mdashhave a range of ways to get around. Dogs, no surprise, are very big on scent, and that can take them a very long way.

“An eleven-mile distance is actually not terribly long for a dog,” says Bonnie Beaver, the executive director of the American College of Veterinary Behaviorists and a professor at Texas A&M University. “If the dog had walked both from and back to his home he’d be following his own scent trail.” In this case, the dog was instead probably following an equally compelling smell: that of its owner, a type of navigation that is entirely possible over long distances as long as the wind is right.

Dogs extend their scent range by moving among overlapping circles of familiar scents&mdashmuch the way cell phone coverage relies on interconnected footprints from different cell towers. A dog that wanders out of its own immediate range might pick up the scent of, say, a familiar dog in the next circle. That might point it to a circle that contains a familiar person or tree or restaurant trash can, and so on.

Cats, like other animals, might rely more on magnetic fields&mdasha faculty that could turn out to be quite common in mammals. “There are some studies that show that the ears of most mammals contain iron,” Beaver says. “That may cue them into the magnetic direction in the ground. There’s work showing that cattle, deer and voles tend to orient in a north-south direction.”

The overall temperament of an animal&mdashor, more broadly, of the species&mdashcan play a role in navigation too. A dog that travels a great distance to get home is likely trying to return to its owner, since the dog-human bond is a powerful one. A cat that travels the same distance is&mdashsorry cat owners&mdashprobably just tying to return to its territory.

No matter how well animals navigate, scientists caution against an observation bias that may make them seem better than they are. A dog or cat that finds its way halfway across the state makes news the uncounted others that stay lost do not. What’s more, some cases of remarkable returns may turn out to be matters of mistaken identity, unless there’s a positive way to identify an animal like an implanted microchip that some owners use along with a collar.

“You hear these stories about a three-legged black cat that came home and jumped into its favorite chair,” says Beaver. “But it’s real hard to be sure because they’ve been gone a long time and they look scruffy. And heck, that chair would be a comfortable one for any cat.”

Still, we shouldn’t dismiss all the stories out of hand. That cat that traveled 200 miles in 2013? It did have an implanted microchip. So kudos to at least one kitty&mdashand probably a whole lot more.

Can Dogs Smell Family Members?

Dogs can sniff out even the faintest of smells. Whether it’s sniffing out illegal substances or simply a tasty treat that’s hidden away, it seems to be their superpower. But, can they use it for recognition?

This leads us to ask exactly what can dogs smell and why are their noses so powerful? In this article, we will take a look at if they are able to sniff out their own family members.

Signs Dogs Can Smell Family Members

Your dog’s wiggling nose shows you that they have a powerful nose for scents. Family members provide praise, attention, and food while your dog takes in the family members’ scents. In turn, this means these scents are associated with good things, and therefore your dog will have formed an attachment to your family’s scents.

Think about when you or another member of the family walk into a room, your dog will look up and wiggle their nose at you. This shows that they recognize who you are and usually even before they've even set their eyes on you. Occasionally, dogs look like they smile at their owners/families, and this is probably just them opening their mouth so they can smell more of what they like.

No doubt you’ll have come across moments where your dog is snuggled up in the family’s dirty washing, and this is all related to the fact they are attached to the scent of the family and take comfort from it. After all, everyone feels secure and calmer when they are surrounded by what they love.

Signs that reveal that your dog knows the scent of your family are things such as head tilting, staring, smiling action, coming to you when you enter a room, and acting alert.

Body Language

  • Staring
  • Alert
  • Barking
  • Head tilting
  • Wag tail
  • Sniffing

Other Signs

  • Turning to look when a family member comes in the room
  • Laying in dirty laundry
  • Twitching their nose

History Behind Dogs Smelling Family Members

Evolution has enabled a dog’s sense of smell to develop, as it’s crucial for survival. Approximately 15,000 years ago, it was believed that evolution changed dogs. Wolf pups were taken by hunter-gatherers and raised for protection and hunting.

As time went on, dogs have become domesticated and fulfilled the roles given to them by humans. As evolution proceeded up until today, dogs continued to fulfill these roles and some of these roles are linked to relying on scents.

Many people believe that as dogs have become domesticated, they’ve also become more aware of human behavior and their social skills have improved. In turn, they are now less attuned to their instincts or survival strategies.

Dogs have learned to link human scents with positive outcomes. This association has created a strong bond between a dog and its family, and the smell of a dog’s family has become a pleasant scent for a dog, even though dogs don’t generally like the smell of humans. Studies have also highlighted that dogs do react favorably to the smell of their owner and their family. A dog is able to recognize the scent of their own family.

Science Behind Dogs Smelling Family Members

A dog’s sense of smell is a lot more powerful than ours. Unlike humans, a dog is able to smell in each individual nostril and therefore has the ability to perceive the world through their nose.

Studies have been conducted to see if a dog can remember the scent of its owner. One particular study looked at the emotional reactions of a dog when they were provided with the scent of their owner compared to the scent of someone else. Brain waves of 12 different breeds of dogs were collected as dogs were exposed to these scents. The results revealed that the response that the dogs displayed were the strongest when they smelled the scents of their owners or humans that were familiar to them.

This goes to show that dogs have a stronger connection with the humans that they know - their family. This is probably related to the fact that they associate the scents given off by their family with play, affection, safety, food, and praise.

Training a Dog to Smell Family Members

Trainers use a dog’s natural smelling instinct to concentrate on signals and commands. Through repetition, the scent for a reward becomes linked to a command given by a human. When you praise your dog, your dog takes in your scent and the fact that they are given a reward/treat, and this then creates a positive feeling that is consequently stamped on your dog’s brain.

Those that own sporting dogs use scent-related work to enhance their bond with them, as well as to teach a dog how to be an ally when it comes to hunting. In the beginning, training is related to understanding basic commands, and this then moves on to locating objects in return for a reward, such as food and praise.

Next, a dog needs to be taken to a place where there are no distractions so that they can begin training. Dogs need to be trained with games that enable them to distinguish between different scents. Here’s a game that you can teach your dog:

Start the game by holding an item in each hand.

Hold your hands near to the dog’s face.

Once your dog picks the hand that has the scent that you want them to detect, reward the dog.

This game can then move on to games that are related to scent discrimination. In these games, a scent needs to be detected but it is hidden among other scents. With time, your dog’s detection skills will improve, and these games will need to move on to a larger scale. Eventually, your dog should be able to locate a scent in a field as if they are part of a hunting team.

When your dog does something that shows you they recognize your smell and the smell of your family, praise them so that they positively associate with your smell and your family’s.

A Heartwarming Reunion

“Studies show that dogs display greater affection toward their owners if they've been separated for longer periods of time,” writes Animal Planet. “As the amount of time away increases, so does the dog’s excitement.” This is exactly why the soldier’s dog greets her with love and affection, even after years of deployment. It’s also a reason why some dogs suffer from separation anxiety when their masters are away. Ask your dog’s caretaker if he's been suffering from anxiety. If so, stage the reunion in a quiet, secluded place where your dog won’t be bombarded with people and attention. It’s a good idea to reunite at home or in a secluded park, separately from your reunions with friends and family. Your dog is going to be happy and relieved to see you, so it's important to give him your full and undivided attention.


Dogs have often been used in studies of cognition, including research on perception, awareness, memory, and learning, notably research on classical and operant conditioning. In the course of this research, behavioral scientists uncovered a surprising set of social-cognitive abilities in the domestic dog, abilities that are neither possessed by dogs' closest canine relatives nor by other highly intelligent mammals such as great apes. Rather, these skills resemble some of the social-cognitive skills of human children. [2] This may be an example of convergent evolution, which happens when distantly related species independently evolve similar solutions to the same problems. For example, fish, penguins and dolphins have each separately evolved flippers as solution to the problem of moving through the water. With dogs and humans, we may see psychological convergence that is, dogs have evolved to be cognitively more similar to humans than we are to our closest genetic relatives. [3] : 60 [4]

However, it is questionable whether the cognitive evolution of humans and animals may be called "independent". The cognitive capacities of dogs have inevitably been shaped by millennia of contact with humans. [5] [6] As a result of this physical and social evolution, many dogs readily respond to social cues common to humans, [7] [8] [9] quickly learn the meaning of words, [10] show cognitive bias [11] and exhibit emotions that seem to reflect those of humans. [12]

Research suggests that domestic dogs may have lost some of their original cognitive abilities once they joined humans. For example, one study showed compelling evidence that dingoes (Canis dingo) can outperform domestic dogs in non-social problem-solving experiments. Another study indicated that after being trained to solve a simple manipulation task, dogs that are faced with an unsolvable version of the same problem look at a nearby human, while socialized wolves do not. Thus, modern domestic dogs seem to use humans to solve some of their problems for them. [3] [13]

In 2014, a whole genome study of the DNA differences between wolves and dogs found that dogs did not show a reduced fear response, they showed greater synaptic plasticity. Synaptic plasticity is widely believed to be the cellular correlate of learning and memory, and this change may have altered the learning and memory abilities of dogs. [14]

Most modern research on dog cognition has focused on pet dogs living in human homes in developed countries, which is only a small fraction of the dog population and dogs from other populations may show different cognitive behaviors. [15] Breed differences possibly could impact on spatial learning and memory abilities. [16]

The first intelligence test for dogs was developed in 1976. It included measurements of short-term memory, agility, and ability to solve problems such as detouring to a goal. It also assessed the ability of a dog to adapt to new conditions and cope with emotionally difficult situations. The test was administered to 100 dogs and standardized, and breed norms were developed. [17] Stanley Coren used surveys done by dog obedience judges to rank dog breeds by intelligence and published the results in his 1994 book The Intelligence of Dogs.

Perception refers to mental processes through which incoming sensory information is organized and interpreted in order to represent and understand the environment. [18] Perception includes such processes as the selection of information through attention, the organization of sensory information through grouping, and the identification of events and objects. In the dog, olfactory information (the sense of smell) is particularly salient (compared with humans) but the dogs senses also include vision, hearing, taste, touch and proprioception. There is also evidence that dogs sense the earth's magnetic field.

One researcher has proposed that dogs perceive the passing of time through the dissipation of smells. [19] [20]

The concept of "object permanence" refers to the ability of an animal to understand that objects continue to exist even when they have moved outside of their field of view. This ability is not present at birth, and developmental psychologist Jean Piaget described six stages in the development of object permanence in human infants. A similar approach has been used with dogs, and there is evidence that dogs go through similar stages and reach the advanced fifth stage by an age of 8 weeks. At this stage they can track "successive visible displacement" in which the experimenter moves the object behind multiple screens before leaving it behind the last one. It is unclear whether dogs reach Stage 6 of Piaget's object permanence development model. [21] [22]

A study in 2013 indicated that dogs appear to recognize other dogs regardless of breed, size, or shape, and distinguish them from other animals. [23]

In 2014, a study using magnetic resonance imaging demonstrated that voice-response areas exist in the brains of dogs and that they show a response pattern in the anterior temporal voice areas that is similar to that in humans. [24]

Social learning: observation and rank Edit

Dogs are capable of learning through simple reinforcement (e.g., classical or operant conditioning), but they also learn by watching humans and other dogs. [22] [25]

One study investigated whether dogs engaged in partnered play would adjust their behavior to the attention-state of their partner. The experimenters observed that play signals were only sent when the dog was holding the attention of its partner. If the partner was distracted, the dog instead engaged in attention-getting behavior before sending a play signal. [26]

Puppies learn behaviors quickly by following examples set by experienced dogs. [22] This form of intelligence is not particular to those tasks dogs have been bred to perform, but can be generalized to various abstract problems. For example, Dachshund puppies were set the problem of pulling a cart by tugging on an attached piece of ribbon in order to get a reward from inside the cart. Puppies that watched an experienced dog perform this task learned the task fifteen times faster than those left to solve the problem on their own. [22] [27]

The social rank of dogs affects their performance in social learning situations. In social groups with a clear hierarchy, dominant individuals are the more influential demonstrators and the knowledge transfer tends to be unidirectional, from higher rank to lower. In a problem-solving experiment, dominant dogs generally performed better than subordinates when they observed a human demonstrator's actions, a finding that reflects the dominance of the human in dog-human groups. Subordinate dogs learn best from the dominant dog that is adjacent in the hierarchy. [28]

Following human cues Edit

Dogs show human-like social cognition in various ways. [7] [8] [29] For example, dogs can react appropriately to human body language such as gesturing and pointing, and they also understand human voice commands. [30] In one study, puppies were presented with a box, and shown that, when a handler pressed a lever, a ball would roll out of the box. The handler then allowed the puppy to play with the ball, making it an intrinsic reward. The pups were then allowed to interact with the box. Roughly three quarters of the puppies subsequently touched the lever, and over half successfully released the ball, compared to only 6% in a control group that did not watch the human manipulate the lever. [31]

Similarly, dogs may be guided by cues indicating the direction of a human's attention. [22] In one task a reward was hidden under one of two buckets. The experimenter then indicated the location of the reward by tapping the bucket, pointing to the bucket, nodding at the bucket, or simply looking at the bucket. The dogs followed these signals, performing better than chimpanzees, wolves, and human infants at this task even puppies with limited exposure to humans performed well. [32] ( pp1634–6 )

Dogs can follow the direction of pointing by humans. New Guinea singing dogs are a half-wild proto-dog endemic to the remote alpine regions of New Guinea and these can follow human pointing as can Australian dingoes. These both demonstrate an ability to read human gestures that arose early in domestication without human selection. Dogs and wolves have also been shown to follow more complex pointing made with body parts other than the human arm and hand (e.g. elbow, knee, foot). [33] Dogs tend to follow hand/arm pointed directions more when combined with eye signaling as well. In general, dogs seem to use human cues as an indication on where to go and what to do. [34] Overall, dogs appear to have several cognitive skills necessary to understand communication as information however, findings on dogs' understanding of referentiality and others' mental states are controversial and it is not clear whether dog themselves communicate with informative motives. [35]

For canines to perform well on traditional human-guided tasks (e.g. following the human point) both relevant lifetime experiences with humans—including socialization to humans during the critical phase for social development—and opportunities to associate human body parts with certain outcomes (such as food being provided by humans, a human throwing or kicking a ball, etc.) are required. [36]

In 2016, a study of water rescue dogs that respond to words or gestures found that the dogs would respond to the gesture rather than the verbal command. [37]

Episodic memory Edit

Dogs have demonstrated episodic-like memory by recalling past events that included the complex actions of humans. [38] In a 2019 study, a correlation has been shown between the size of the dog and the functions of memory and self-control, with larger dogs performing significantly better than smaller dogs in these functions. However, in the study brain size did not predict a dog's ability to follow human pointing gestures, nor was it associated with their inferential and physical reasoning abilities. [39] A 2018 study on canine cognitive abilities found that various animals, including pigs, pigeons and chimpanzees, are able to remember the what, where and when of an event, which dogs cannot do. [40]

Learning and using words Edit

Various studies have shown that dogs readily learn the names of objects and can retrieve an item from among many others when given its name. For example, in 2008, Betsy, a Border Collie, knew over 345 words by the retrieval test, and she was also able to connect an object with a photographic image of the object, despite having seen neither before. [41] In another study, a dog watched as experimenters handed an object back and forth to each other while using the object's name in a sentence. The dog subsequently retrieved the item given its name. [42]

In humans, "fast mapping" is the ability to form quick and rough hypotheses about the meaning of a new word after only a single exposure. In 2004, a study with Rico, a Border Collie, showed he was able to fast map. Rico initially knew the labels of over 200 items. He inferred the names of novel items by exclusion, that is, by knowing that the novel item was the one that he did not already know. Rico correctly retrieved such novel items immediately and four weeks after the initial exposure. Rico was also able to interpret phrases such as "fetch the sock" by its component words (rather than considering its utterance to be a single word). Rico could also give the sock to a specified person. This performance is comparable to that of 3-year-old humans. [10]

In 2013, a study documented the learning and memory capabilities of a Border Collie, "Chaser", who had learned the names and could associate by verbal command over 1,000 words at the time of its publishing. Chaser was documented as capable of learning the names of new objects "by exclusion", and capable of linking nouns to verbs. It is argued that central to the understanding of the Border Collie's remarkable accomplishments is the dog's breeding background—collies bred for herding work are uniquely suited for intellectual tasks like word association which may require the dog to work "at a distance" from their human companions, and the study credits this dog's selective breeding in addition to rigorous training for her intellectual prowess. [43]

Some research has suggested that while dogs can easily make a distinction between familiar known words and nonsensical dissimilar words, they struggle to differentiate between known familiar words and nonsense words that differ by only a single sound, as measurements of the dogs' brain activity showed no difference in response between a known word and a similar but nonsensical word. This would give dogs the word processing capability equivalent to the average 14-month human infant. [44]

Studies suggest that dogs feel complex emotions, like jealousy and anticipation. [45] [46] However, behavioral evidence of seemingly human emotions must be interpreted with care. For example, in his 1996 book Good Natured, ethologist Frans de Waal discusses an experiment on guilt and reprimands conducted on a female Siberian Husky. The dog had the habit of shredding newspapers, and when her owner returned home to find the shredded papers and scold her she would act guilty. However, when the owner himself shredded the papers without the dog's knowledge, the dog "acted just as 'guilty' as when she herself had created the mess." De Waal concludes that the dog did not display true guilt as humans understand it, but rather simply the anticipation of reprimand. [47]

One limitation in the study of emotions in non-human animals, is that they cannot verbalise to express their feelings. However, dogs' emotions can be studied indirectly through cognitive tests, called cognitive bias test, which measure a cognitive bias and allow to make inference about the mood of the animal. Researchers have found that dogs suffering from separation anxiety have a more negative cognitive bias, compared to dogs without separation anxiety. [48] On the other hand, when dogs' separation anxiety is treated with medications and behaviour therapy, their cognitive bias becomes less negative than before treatment. [49] Also administration of oxytocin, rather than a placebo, induces a more positive cognitive bias and positive expectation in dogs. [50] It is therefore suggested that the cognitive bias test can be used to monitor positive emotional states and therefore welfare in dogs. [50] [51]

There is evidence that dogs can discriminate the emotional expressions of human faces. [52] In addition, they seem to respond to faces in somewhat the same way as humans. For example, humans tend to gaze at the right side of a person's face, which may be related to the use of right brain hemisphere for facial recognition. Research indicates that dogs also fixate the right side of a human face, but not that of other dogs or other animals. Dogs are the only non-primate species known to do so. [53]

Sex-specific dynamics are an important contributor to individual differences in cognitive performance of pet dogs in repeated problem-solving tasks. [54]

Captive-raised dingoes (Canis dingo) can outperform domestic dogs in non-social problem-solving. [55] Another study indicated that after undergoing training to solve a simple manipulation task, dogs faced with an unsolvable version of the same problem look at the human, whereas socialized wolves do not. [29] [56] Modern domestic dogs use humans to solve their problems for them. [3] [57]

Dogs have been shown to learn by making inferences in a similar way to children. [58] [3] : 170–180

Dogs have the ability to train themselves and learn behaviors through interacting and watching other dogs. [59]

"Theory of mind" is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires, intentions, and perspectives that are different from one's own. [60] There is some evidence that dogs demonstrate a theory of mind by engaging in deception. For example, one observer reported that a dog hid a stolen treat by sitting on it until the rightful owner of the treat left the room. [22] Although this could have been accidental, it suggests that the thief understood that the treat's owner would be unable to find the treat if it were out of view. [22] [26] A study found that dogs are able to discriminate an object that a human partner is looking for based on its relevance for the partner and they are more keen on indicating an object that is relevant to the partner compared to an irrelevant one this suggests that dogs might have a rudimental version of some of the skills necessary for theory of mind. [61]

Studies Show Dogs Recognize by the Smell

A new study, which was published in Pacific Standard earlier this year [1], demonstrated that when a dog smells a familiar human, there is a specific area of their brain that is being triggered.

Dogs use the smells, sights, sounds, and other sensations that are provided by humans to distinguish one person from another. When the sensations of a certain person are activated, a dog will behave in the way they usually do around that human. It may be shown as a special greeting, sniffing the person’s pockets if they usually bring treats, or barking a welcome.

Typically, when a dog’s owner leaves, they go through a grieving period and, much like people, it can last anywhere from a few days to a few months.

Because we cannot communicate with our pets and let them know when we will be back, a lengthy separation becomes an unpredictable loss to them, and a true anxiety problem.

7 Amazing Facts About Your Dog’s Sense of Smell

People have known for millennia that a dog&rsquos sense of smell is very different than ours. But science has recently learned all kinds of wow-worthy info about our dogs&rsquo olfaction. Check out seven of latest, greatest findings about a dog&rsquos sense of smell.

A dog&rsquos sense of smell is much stronger than a human&rsquos sense of smell. Photography ©BiMKA | Thinkstock.

1. A dog&rsquos sense of smell is way stronger than ours

Yeah, you can read that two ways, but think back to what your dog smells like when wet, and you&rsquoll figure out the right meaning. When it comes to nose sensitivity, dogs are the paws-down winners over humans. Numbers abound about how much better a dog&rsquos sense of smell is than ours. There are so many variables that it&rsquos almost impossible to quantify. I&rsquove seen figures indicating that a dog&rsquos sense of smell is from 10 to 100 to 1,000 to 1,000,000 times better. Scientists I&rsquove spoken with say that dogs can detect some, if not most, odors at concentrations of parts per trillion.

Psychologist and prolific dog book author Stanley Coren gave me an example of what that huge sniffer sensitivity looks like. Let&rsquos say you have a gram of a component of human sweat known as butyric acid. Surprisingly, humans are quite good at smelling this. If you let it evaporate in the space of a 10-story building, many of us would still be able to detect a faint scent upon entering the building. Not bad, for a human nose. But consider this: If you put the 135-square-mile city of Philadelphia under a 300-foot-high enclosure, evaporated the gram of butyric acid and let a dog in, the average dog would still be able to detect the odor.

2. To a dog, you stink

As clean as you are, and as much soap and perfume and deodorant you wear, you are still splendidly stinky to your dog. Every human has a unique scent fingerprint, and that&rsquos pretty much everything a dog needs to tell one person from another. &ldquoTo our dogs, we are our scent,&rdquo says canine cognition expert Alexandra Horowitz, author of the enlightening book, Inside of a Dog: What Dogs See, Smell, and Know. In that book, she writes this wonderful description about a dog&rsquos sense of smell:

&ldquoHumans stink. The human armpit is one of the most profound sources of odor produced by any animal our breath is a confusing melody of smells our genitals reek. The organ that covers our body &mdash our skin &mdash is itself covered in sweat and sebaceous glands, which are regularly churning out fluid and oils holding our particular brand of scent. When we touch objects, we leave a bit of ourselves on them a slough of skin, with its clutch of bacteria steadily munching and excreting away. This is our smell, our signature odor.&rdquo

3. A dog&rsquos sense of smell picks up all sorts of invisible things

With every step you take, you shed loads of skin flakes &mdash kind of like the Peanuts character Pigpen and his ubiquitous dirt cloud. Real people have the same billow, only it&rsquos made up of skin cells, which, when in this flake form, are known as rafts, or scurf.

Get this: We shed 50 million skin cells each minute. Wow! &ldquoThey fall like microscopic snowflakes,&rdquo Coren says. I am sitting here only moving my fingers on my keyboard because I really don&rsquot want to shed, but no matter what I do, I&rsquom just a snowstorm. Thankfully, we can&rsquot see this winter wonderland ourselves. But these rafts and scurf, with their biological richness, including the bacteria that sheds with them, are very &ldquovisible&rdquo to dogs&rsquo noses.

4. You can&rsquot fool your dog&rsquos sense of smell

Research indicates that it&rsquos quite likely that a dog&rsquos sense of smell can pick up fear, anxiety and even sadness. The flight-or-fight hormone, adrenaline, is undetectable by our noses, but dogs can apparently smell it. In addition, fear or anxiety is often accompanied by increased heart rate and blood flow, which sends telltale body chemicals more quickly to the skin surface. Trying to mask your strong feelings with a casual smile may fool your friends, but it&rsquos not going to fool a dog&rsquos sense of smell.

5. Dogs use their smell to send messages through peeing

I love this description of dog communiques from Coren: &ldquoDogs read about the world through their noses, and they write their messages, at least to other dogs, in their urine.&rdquo It&rsquos tempting to drag your dog along on a walk when he&rsquos sniffing everything annoyingly slowly, but give him chance to read the neighborhood gossip column, and let him do a little writing while he&rsquos at it.

6. This is what&rsquos happening when dogs smell each other&rsquos nether regions

When dogs start sniffing each other&rsquos nether regions, chances are they&rsquore learning far more about each other than you and the other dog&rsquos owner are learning through idle chitchat. Exactly what the dogs are learning, and what they do with that information, has yet to be figured out by science. But it&rsquos very likely far beyond &ldquoNice weather we&rsquore having, eh?&rdquo It&rsquos probably more along the lines of, &ldquoOh, you&rsquore a nice dog, and you had chicken recently, and you&rsquore about, um, 10 years old?&rdquo

7. Scientists are studying dogs&rsquo noses as never before

Maybe it&rsquos because of dogs&rsquo role in the military as incomparable IED detectors. (See my book Soldier Dogs for lots more on how dogs do their job in the military.) Or maybe it&rsquos that dog noses and a dog&rsquos sense of smell are just so amazing, and the more we know, the more we want to know. A dog&rsquos sense of smell is being studied more than ever at universities around the world. But to get to some of the more interesting research, you have to read through papers with titles like, The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of macrosmia. (Does Google offer a translation programs for scientific lingo?)

I look forward to sniffing out what they come up with next in regard to a dog&rsquos sense of smell.

This piece was originally published in 2017.

Thumbnail: Photography ©Kira-Yan | iStock / Getty Images Plus.

Do Dogs Forget Their People?

Let’s say your long-term relationship totally implodes. Browsing for a new apartment, or a therapist that takes your insurance, you hear your dog bark in the other room—and realize, with a start, that it’s not actually your dog. Once you’re all moved out, the dog will be out of your life, too. Stewing in self-pity you think—and subsequently become convinced—that this dog, who you’ve fed and bathed who knows how many times, and coined several adorable nicknames for, will forget you ever existed by the start of next spring.

Probably, for your own health, you should just avoid those kinds of thoughts. Still, the question remains: Are you correct? Can a dog forget one of the people in its life, if that person suddenly leaves it for a long (or long-ish) period of time? To find out, for this week’s Giz Asks we reached out to a number of experts in canine behavior, psychology and medicine. As it turns out, this facet of dog-memory is difficult to study: systematic research on the subject is close to non-existent. But a vast body of anecdotal evidence suggests that, barring a neurodegenerative illness, your dog will probably never fail to recognize you.

Sarah-Elizabeth Byosiere

Lecturer and Coordinator, Companion Animal Cognition Center, Animal Behavior and Conservation Program, Hunter College

Most pet owners will agree that their pets can remember things. One example: a dog getting excited to head out for a walk after seeing or hearing a leash. Or a dog learning to associate commands with actions—sitting when told to sit. These reflect semantic memory, a type of explicit memory, where previously learned information is recalled.

Evidence for semantic memory in animals has been observed across a variety of species. In dog cognition studies, many experimental paradigms utilize a dog’s semantic memory to assess other aspects of their cognitive abilities. However, the question of “can dogs forget their owners?” employs another type of explicit memory called episodic memory.

Episodic memory refers to memories of autobiographical events—in other words, recalling personal experiences. Endel Tulving, who defined episodic and semantic memory, proposed that conscious recollection was required to demonstrate episodic memory. Given that we have no good way of evaluating consciousness, also known as self-awareness, in animals, it is incredibly challenging to suggest that dogs, or other animals, have episodic memory.

To get around this definitional constraint, researchers have separated the behavioral criteria required for episodic memory from the conscious component and termed this “episodic-like” memory. Using this definition, animal behavior researchers can now evaluate whether or not animals behaviorally demonstrate the recalling of autobiographical events.

To date, there is evidence that some non-human animals, such as great apes, dolphins and scrub jays may possess some form of episodic-like memory. But how about our dogs? Are they capable of episodic-like memory? Can they remember us—or forget us? In a 2016 study, Claudia Fugazza and colleagues evaluated episodic-like memory in dogs. The results suggest that dogs can recall their owner’s actions, even in instances in which they were not explicitly commanded to do so. These findings indicate that dogs may have episodic-like memory in which memories are linked to specific times and places.

While we may not yet know the answer to “can dogs forget their owners?”, it seems plausible that the evidence for episodic-like memory, in the form of memories related to time and space, may extend to remembering things like “who”. We need more research to uncover the answer to this question, but for now, it’s nice to come home to a dog, that in our mind, appears happy to see us.

Stefano Ghirlanda

Professor, Psychology, Brooklyn College and the CUNY Graduate Center, and Guest Professor at Stockholm University, whose research focuses on animal learning and memory

Many animals have excellent long-term memory. A long-term memory, as the name suggests, can remain intact without significant degradation for years. Anecdotes about pets recognizing their first owner, or another significant person in their life, after many years are supported by experiments on animal memory, in which animals have been trained to identify images and then had their memory tested months or even years later. In fact, even pigeons, who are not considered overly intelligent by lay people, can remember hundreds of images for many months.

The question is more whether the memory is formed in the first place than whether it will be remembered, once formed. For the most part, animals form long-term memories of events and situations that they deem meaningful. If a person is particularly mean to the animal, they might form right away a very strong aversive memory, and thereafter react with fear or aggression. If a person forges a long term bond through daily, positive interactions, that person will likewise be remembered for many years. I am not positive that casual acquaintances will be remembered as well.

Memories of other beings (animal or human) are more easily formed in social animals, such as dogs, horses, or parrots. Cats are more solitary and therefore they do not feel strongly about the mere presence of other beings. At the same time, it’s hard to imagine that extensive positive interaction will not form a memory at all. Moreover, because they are less social, cats are also less expressive of their emotions, so they might still remember someone but not be very vocal about it. I’m afraid this will be another point of argument between dog people and cat people.

Rachelle Yankelevitz

Assistant Professor, Psychology, Rollins College, with research interests in human and non-human decision making, impulsivity, risk taking, and animal behavior

Forgetting, remembering, love, and attachment. These words describe the human experience of finding pleasure in another. Sometimes when we are away from the other person, we think about them, and then we experience joy at seeing them once again. For people, these processes involve language, which enables us to handle abstract concepts and talk about events that happened in the past. For dogs, there is no evidence that they have this internal monologue. Fortunately, learning can also involve non-language associations between events, such as when we associate a smell with a pleasant occurrence, or when we start spending more time with someone because they make us feel good. These associations can happen without our being able to describe what is happening, and they can last our entire lives with only a few initial experiences. These associative processes (respondent and operant conditioning) are how dogs learn.

Sometimes these associations do not serve us well in our daily lives we seek to forget painful or irrelevant associations. One way to forget is to undergo counterconditioning, or systematic desensitization. Associations can also break over the passage of time, if we go without exposure to relevant cues.

For all of us, the durable nature of associations with others is a double-edged sword. For example, a dog might respond to a previous caregiver they haven’t seen in years with exuberant butt-wiggling, and a dog’s fear of men in baseball caps might also endure for years. Animal shelter staff and volunteers are familiar with the counterconditioning process in which they overcome a dog’s negative experiences with people in the past by creating a new association: people equal treats/toys/good times. For a dog with a lot of negative past experiences, this process is slow and deliberate, and the trainer minimizes threatening stimuli by introducing new things carefully. Dogs, like people, learn best when they’re calm. In time, and with the trainer’s skill, the past is less influential on the dog’s behavior, and the dog learns that people are fun. For dogs with positive past experiences, these associations with their previous owner also fade over time as new sources of treats and cuddles arise.

So, yes, dogs can forget. While the idea that our pet could forget about us may be disappointing, this ability to forget is actually something that we admire most about dogs: they don’t hold grudges, and they are remarkably adaptable to their current settings. Without the internal language processes of pondering, rumination, obsession, and analysis, they live in a simpler world of forgiveness and new beginnings.

Lynette Hart

Professor, Human-Animal Interactions and Behavior, UC Davis School of Veterinary Medicine

There are no controlled studies of this that come to mind. However, the greeting behavior of dogs is consistent, and a feature viewed by owners as a characteristic of a perfect dog—and dog owners rate their dogs as excellent on this trait. It’s an example of built-in compatibility and shows that dogs recognize their people. However, as dogs age some have cognitive deficits and no longer recognize their owners, which can be very distressing. Long term caregivers of elephants sometimes have not seen the elephant for even decades and then been fully recognized by the elephant.

Ruth Colwill

Professor, Psychology, Brown University, specializing in animal learning and behavior, particularly in dogs

College students going home for winter break will undoubtedly be greeted ecstatically by the canine sibling they left behind and feel re-assured that they were not forgotten. Such were the experiences described by the Nobel prizewinning ethologist Konrad Lorenz in his insightful book Man Meets Dog. For example, returning home after nine months, Lorenz describes how Stasi first catches his scent, then howls deliriously for more than a minute before bounding and leaping towards him in frenzied excitement. The intensity of her welcome is hard to explain in any way other than that she recognized her owner.

But might a dog forget her absentee pack member after a longer separation? It seems unlikely for a number of reasons. Odor memories appear to be extremely robust and long-lasting. The French writer Marcel Proust famously describes the evocative power of the scent of a Madeleine biscuit soaked in tea to transport him back in time to his aunt’s kitchen. With a nose and brain built to process olfactory stimuli, a dog is not likely to forget what scents mean, especially when they belong to members of their family and have strong emotional connections. Additionally, contextual cues are known to aid memory retrieval, which would facilitate the dog’s ability to recognize the odor walking through the front door. But there may be an exception. Like humans, dogs are living longer and, like humans, they can develop symptoms of dementia. A dog with canine cognitive dysfunction might forget his owner but how would we really know? The lack of a response can be very difficult to interpret.

Nicholas Dodman

Professor Emeritus, Clinical Sciences, Tufts University, founder of the Animal Behavior Clinic and author of many books, most recently Pets on the Couch: Neurotic Dogs, Compulsive Cats, Anxious Birds, and the New Science of Animal Psychiatry

Canine Alzheimer’s is definitely a real condition. I do call it Canine Alzheimer’s—the purists will say, “well, it’s not exactly the same,” but it kind of is exactly the same, right down to the changes that occur in the brain. In humans with Alzheimer’s, there’s a build-up in the brain of a protein called amyloid. (There’s another protein involved, but amyloid is the main culprit.) The degree to which the brain is affected correlates precisely with the degree of psychomotor impairment in the person, and the same is true in dogs. One of the cardinal signs of Alzheimer’s is disorientation, and disorientation involves not recognizing familiar people. So disease can cause it, and I imagine there are other neurological conditions that could as well.

But you look at all the videos on YouTube of soldiers who’ve been away in various theaters of war for long periods of time—they return and the pet goes absolutely ballistic. Or think of the famous story of Greyfriars Bobby in Edinburgh, Scotland—this was a dog whose owner died and was interred in a church graveyard, and apparently the dog spent the next nine or ten years just sitting on the grave, waiting for his master to come back. And there was a Japanese dog who always met his owner off the train at a certain time, and who still went down to meet the train for years after the owner died of a heart attack, hoping he would get off.

These stories sort of confirm that dogs have incredibly long memories for people they’re fond of. And with people they’re fond of, they remember everything about them—every nuance, from appearance to smell. All their sense are acutely tuned to that person.

Clive Wynne

Professor and Area Head, Behavioral Neuroscience, Arizona State University and head of the Canine Science Collaboratory

Darwin, when he went around the world on the Beagle, was very impressed by the fact that when he got home four years later his dog clearly recognized him. And plenty of less famous people than Darwin have had the same experience.

But as for the reverse—cases where people were away from their dog for some period of time, and the dog did not recognize them when they returns—I cannot think of any instance where that happened. It’s one of those things that might have happened, but nobody would want to boast about it.

But just because dogs remember their people for years doesn’t mean it’s cruel to rehome a dog. I feel very strongly that more people should be adopting older dogs, or dogs from shelters, as opposed to thinking you have to have a puppy—thinking that you wont really have a loving animal if you didn’t know the dog when it was a puppy. And that’s just not true. Dogs can form strong emotional bonds with people even if they don’t meet those people until considerably later in their lives.


A dog’s sense of touch is the very first sense to develop and, for the first few weeks of their life, the one they rely on and learn the most from. Your dog’s sense of touch is involves both him touching other objects and also how he is touched. A dog’s entire body is covered in touch-sensitive nerve endings that “feel” the world around him, the wind blowing or a fly landing on his back, for example. And, dog’s have touch-sensitive hairs called vibrissae – better known as their whiskers – on their muzzle and above their eyes.

Dogs continually use their sense of touch to communicate with other dogs and with you. Physical affection, petting, scratching, and massage are all positive and important ways to communicate to your dog through touch. Another great way to show affection through touch that your dog will absolutely love (and he’ll benefit from, too) is brushing! Using a massaging dog brush, gently stroke your dog’s body, activating those nerve-endings, loosening hair, and giving his coat a great shine.

Acknowledging Your Voice

Some experts have speculated that human faces just aren’t as important to cats. Unlike dogs, cats joined human society on their own terms. Rodents came to human villages to eat grain stored there, and cats came to hunt the rodents. Cats never needed to read human gestures and expressions in the same way that dogs did and, as a result, they may not have developed the same understanding of human faces.

It’s more likely that cats recognize us in other ways, like scent, touch, and sound. A 2013 study by scientists at the University of Tokyo found that cats can tell recordings of their owners’ voices apart from strangers’ voices. The cats in the study mostly ignored the recordings of strangers calling their names but twitched their ears to listen more closely to their owners’ voices. Of course, none of the cats in the study actually got up to look for their absent owners, because cats know better than to give up a good napping spot.