Exercising and Enhancing the Senses - Sight

We tend to think of humans as visual mammals and dogs as olfactory and auditory mammals, but science is challenging these stereotypes. The visual world we make available to our dogs is worth considering because it can impact their well-being. Let’s consider the canine visual cosmos.

Visual acuity in humans is often described using what’s called the Snellen fraction, which is the well-known ratio of “20/20” or “20/40” that represents the quality of one’s eyesight. Dogs have a Snellen fraction of 20/75. This means that what we can see at 75 feet, a dog can see only at 20 feet. Using this method of measuring acuity, dogs have worse vision than humans. But it would be wrong to claim that dogs don’t see as well as humans, since the Snellen fraction provides only one small window into the larger sense of sight. It would be more accurate to say that dogs and humans see the world differently. The visual acuity of dogs evolved to meet dogs’ unique needs, and different doesn’t necessarily mean better or worse.

Dogs are visual generalists, meaning that their eyes work well in a range of different light levels. They likely can see better at dusk and in the dark than humans. It’s been estimated that dogs can see in light about five times dimmer than humans can. Dogs are also better adapted than humans for identifying movement in their peripheral vision. However, dogs are not as good as humans at seeing things in detail. One reason for this may be that dogs can’t easily distinguish between the colors red and green.1 A red ball thrown in a field of green grass will be challenging to see even for a Labrador retriever. Other aspects of vision include depth perception, visual field of view, and sensitivity to motion. In each of these areas, dog vision is different from human vision as visual capacities have adapted to each species’ needs.

One of our mantras throughout this book is that there is no universal “dog.” Dogs come in a huge variety of shapes and sizes, and their sensory capacities may vary based on these differences. In the realm of sight, for instance, different breeds appear to have different visual strengths. Alexandra Horowitz suggests that variations in canine visual acuity may be related to the shape and size of the nose. Short-nosed dogs like pugs tend to have better up-close vision, while dogs with long noses have better panoramic and peripheral vision.2 This may help explain why short-nosed dogs are often less interested in chasing balls and Frisbees than their longer-nosed kin. It is more difficult for them to see a ball and track its movement, which makes it a lot less interesting to chase.

Many human companions report that their dog will bark at someone wearing a hat or sunglasses or walking on crutches. Dogs often get spooked by things they don’t visually recognize. Loss of visual acuity is common in older dogs, just as it is in people, and dogs who are visually impaired need a little extra help interacting with their world. Their behavior may change, too. At fifteen years of age, Jessica’s dog Maya has lost the use of one eye and has relatively poor vision in the other. She’s started to bark at people on walks, particularly people who stand about three feet away, right in what seems to be a blind spot. Loss of vision can lead to anxiety and social withdrawal, if we aren’t careful to help our canine companions adapt. That said, loss of sight, even complete blindness, does not mean that a dog has poor quality of life. Blind and visually impaired dogs can adapt quite well to their disability, though they need special care and consideration. Often these dogs adapt by relying more heavily on other sensory input, such as sound and smell, and they can be trained to follow olfactory cues or “smell hints,” such as a puff of citrus essential oil.

A challenge for future research with dogs is to learn not only how each sense works on its own but how dogs combine and use the input from multiple senses — how they use composite signals — to understand the world and to make decisions. For instance, one study by dog researcher Ludwig Huber showed that captive dogs could integrate information from sight and sound to identify other dog breeds correctly. In this study, dogs matched a projected visual image of dogs of different sizes with the vocalization that is usually made by dogs of each size.3 This kind of composite signal may help Maya determine, from quite far off, that she sees a poodle, so that she can get her hackles raised in anticipation. For whatever reason (and no offense intended), Maya is not too keen on poodles.

LET DOG-DOG INTERACTIONS FLOW

If you watch a group of dogs playing at a dog park, you will quickly notice how carefully they watch one another. Dogs will look over their shoulders as they run, or they will stop and turn around so they can see what the other dogs are doing. When they do this, they’re reading body postures, gaits, tail and ear positions, facial expressions, and even watching for subtle changes in the position of another dog’s fur, such as whether another dog is showing their hackles. “Hackles” refer to the hairs along a dog’s neck and backbone, and “raised hackles” are called piloerection, an involuntary neural response to arousal mediated by the sympathetic nervous system. Dogs may also gather information by looking in a dog’s eyes, though research in this area is limited. It may be that dilated or constricted pupils communicate something about a dog’s emotional state that other dogs can decipher. In addition to this kaleidoscope of visual signals, dogs are also absorbing olfactory and auditory information, all while on the run, which is quite a remarkable feat.

It’s important for dogs to be able to read one another accurately in order for social interactions to go well. The same is true in the human realm, which is one reason that highly successful people tend to be those with high levels of emotional intelligence and well-honed social skills. One of the reasons dogs can get into sticky situations with one another is when they misread visual or other signals, and some dogs are much better at reading signals than others. Spend any time at a dog park, and you will certainly notice a few dogs who are socially awkward and don’t seem very good at interacting with other dogs. Oftentimes, these dogs have trouble finding play partners. Marc has noted that there often seems to be a relationship between the social skills of a dog, or lack thereof, and those of their human, but that’s another story.4

One of the mysteries of a dog’s world is how they recognize other dogs as belonging to the category “dog.” Obviously, dogs recognize other dogs by smell, but they also seem able to recognize other dogs using only sight. A very interesting study conducted by Dominique Autier-Derian and her colleagues found that dogs can identify other dogs using facial features alone, in the absence of other cues such as movement, scent, and sound. Dogs were very good at picking out the faces of other dogs, among human and other domestic and wild animal faces. C. Claiborne Ray, discussing this study, remarked, “Ranging in size from a tiny Maltese to a giant St. Bernard, and showing myriad differences in coats, snouts, ears, tails and bone structure, dogs might not always appear to belong to one species. Yet other dogs recognize them easily.”5

We often hear dog owners say something like, “My vizsla loves other vizslas more than any other kind of dog, and she also knows they are vizslas.” Can dogs really recognize other dogs of the same breed? Nobody knows, but a lot of anecdotal evidence suggests that they might. If they do, it is likely that the cues lie in the dog’s olfactory sense, and perhaps in the identification of what’s called the major histocompatibility complex, or MHC. The MHC is a set of surface proteins found on the cells of all mammals, and it is involved in immune function. It’s thought to play a role in the selection of mates who are not too closely related genetically. The MHC may present as a kind of olfactory “signature” allowing dogs to determine genetic familiarity, but there hasn’t been any research in this area. Nonetheless, many people believe their dog shows a preference for others of their same breed.

Dogs need to be able to interact with other dogs. This is what dogs are “made” for, if you will. Many of their cognitive skills and the components of their behavioral repertoire have evolved to help them communicate more effectively with others of their own kind. It is sad to think that these amazing capacities could go unused, which is why giving our dogs ample opportunity to interact with other dogs and to practice their communication skills is one of the most important forms of social and cognitive enrichment we can and must provide.

TALES ABOUT TAILS

You may wonder why tails are included in a section on sight. Well, among other things, a dog’s tail is an important visual tool for communication. We can gather a lot of information about what a dog is feeling by observing their tail, and of course, tails are critical to dog-dog interactions. Looking at a tail in isolation, however, never tells the whole story; that would be like reading only part of a sentence. To fully understand what a tail is communicating, it needs to be seen in the context of a broader range of composite signals, including ear positions, facial expressions, body postures, vocalizations, odors, and gait. Tails may also be used to disperse odors, such as the scent from a dog’s lovely information-packed anal gland.

Some interesting research has been done into what different tail movements are trying to communicate. As you likely know, a wagging tail can mean different things, depending on the kind of wag and the context. A loose wag is probably friendly, whereas a stiff wag likely signals assertiveness or aggression. However, there are no hard-and-fast rules.

Research has also shown that tail wagging with a bias to the right indicates that a dog is happy and relaxed, whereas left-bias wagging may indicate anxiety. In one study, dogs seeing their owners were more likely to show high-amplitude wagging with a bias to the right side (showing left-brain activation), while dogs seeing dominant unfamiliar dogs tended to wag to the left (showing right-brain activation).6 These findings are consistent with the hypothesis that dogs have a left-hemisphere specialization for approach behavior and a right-hemisphere specialization for withdrawal behavior. More recent research by the same group of scientists found that dogs respond emotionally to the tail-wagging bias of other dogs. The scientists analyzed the behavior and cardiac activity (a rough measure of calmness or anxiety) of a group of dogs watching images of other dogs wagging. Dogs consistently showed more pronounced emotional reactions to and were stressed by left-wagging tails.7

What if a dog loses their tail? Stanley Coren tells a story about a dog whose tail had to be amputated after an unfortunate dog-motorcycle collision. Other dogs seemed unable to understand what she was trying to communicate.8 Marc’s friend, Marisa Ware, told him the story of her dog, Echo, who lost her tail in an accident. After the loss, Echo changed the way she communicated with dogs and people by using her body and ears to compensate for the loss of her tail. Tailless Echo now relies more heavily on her ears to express her feelings. When she is excited to see someone, she puts her ears very far back and will almost wiggle them. She also has developed a kind of “hop-wiggle,” taking a little hop and wiggling her butt very quickly if she is excited to see someone. Echo never did the “hop-wiggle” before losing her tail.

Even the shortening of a tail, such as through docking, seems to inhibit a dog’s ability to communicate with other dogs. To investigate the role of tail length in dog-dog encounters, a team of researchers built remote-controlled replicas of dogs with different lengths of tail, and they observed more behavioral nuance in the reactions of dogs to long-tailed versus short-tailed replicas. This suggests that more communicative information was gleaned from a long tail, which may mean that a longer tail is more effective at sending messages than a shorter tail.9

The long and short of it is that tails are important to dogs. Thus, tail docking is a freedom inhibitor (and a form of disfigurement) that limits a dog’s ability to communicate. We are in support of enlightened breed standards that don’t involve cutting off puppies’ tails.

DOGS “SPEAK” WITH THEIR EARS

Like a tail, a dog’s ears are an important visual signal in dog-dog and dog-human interactions. The next chapter discusses hearing, while this section considers what ears say by their movement and position. Take the time to watch your dog’s ears closely, since they can be a good indicator of how your dog is feeling. Ears are part of the group of composite signals — which include a dog’s face, body, tail, vocalizations, gait, and odors (some of which we are only partially privy to) — that complete the sentence of what a dog is feeling.

For example, if a dog twitches their ears, moving them back and then forward a bit, it may indicate indecision or ambivalence. Pricked ears signal that a dog is paying attention. If Maya pricks her ears, Bella will immediately respond by barking. Bella’s motto is “bark first, then ask why.” By watching the direction another dog is turning an ear, dogs can find out information about where to look. Ear position is important during dog social encounters, including play. For example, flattened ears can signal submission if combined with submissive body posture, and “up” ears can signal excitement and intention to continue play. Flattened ears might also be a way for a dog to avoid getting them nipped.

We have been asked whether dogs like basset hounds with long, floppy ears have a harder time communicating through ear positions. It’s possible that floppy ears don’t allow for quite as much expressiveness, but we really don’t know.10

As with tails, we support breed standards that don’t involve cropping or otherwise changing the natural shape of a dog’s ears. Doberman pinschers, Boston terriers, and Great Danes are a few of the breeds in which ear cropping is still common. During the ear-cropping procedure, the pinnae (earflaps) are altered. The pinna functions to funnel sound into the ear canal, and so dogs with cropped ears lose some acuity in their hearing; they also lose the ability to rotate the ear fully, and this makes it harder for them to communicate with their ears.

FACE THE FACTS: EXPRESSIONS MATTER

One of the composite signals dogs use to communicate includes facial expressions, and research has shown that dogs pay particularly close attention to human facial expressions — perhaps because we don’t have tails and our ears don’t move. In one study of dogs and human facial expressions, a team of scientists led by Corsin Muller demonstrated that dogs differentiate between happy and angry human faces and that dogs find angry faces to be aversive.11 In a related study, Natalia Albuquerque and colleagues examined the behavior of dogs in response to emotionally relevant visual cues from humans. The team compared the responses of dogs to happy

and angry human facial expressions and found that dogs engaged in mouth-licking in response to angry expressions. Dogs mouth-licked when they saw images of angry human faces, but not when they heard angry voices, emphasizing the importance of the visual cues. Mouth-licking can be an appeasement signal during dog-dog communications, and it may similarly serve as a way for a dog to respond to perceived negative emotion in a human companion. (An “appeasement behavior” inhibits or reduces aggressive behavior of a social partner.) In the study, dogs engaged in mouth-licking more often when looking at images of humans than of other dogs, suggesting that dogs may have evolved their sensitivity to human facial expression to facilitate interactions with us.12

In another study, researchers found that the hormone oxytocin (which is associated with feelings of trust and affection) made dogs interested in smiling human faces and less threatened by an angry face. The researchers gave half of a group of dogs a nasal spray containing oxytocin and half a placebo nasal spray. Those dogs with increased levels of oxytocin spent more time gazing at images of happy human faces than dogs in the placebo group. The researchers also found that in the placebo group, the pupils of the dogs were more dilated when gazing at angry faces, a sign that they found the angry faces aversive. In the oxytocin group this negative emotional response was less pronounced. They concluded, “Oxytocin has the potential to decrease vigilance toward threatening social stimuli and increase the salience of positive social stimuli thus making eye gaze of friendly human faces more salient for dogs.”13 In other words, oxytocin likely plays a key role in the development of the human-canine bond.

Some of the most exciting research into canine cognition has involved the use of functional Magnetic Resonance Imaging (fMRI) to study how dogs’ brains process social information. This research is noninvasive, and the dogs participate voluntarily. Neurobiologist Gregory Berns, working at Emory University, has been interested in facial recognition and whether, like humans and nonhuman primates, dogs have a special region in their brain dedicated to processing faces. It would make sense that dogs evolved the neural machinery to process facial information of other dogs because dogs (and wolves) are highly social mammals. But have dogs also evolved the neural machinery to process human faces, based on their history of domestication and coevolution with humans? Berns and his colleagues found that dogs do, indeed, have a dedicated region of the brain for processing human faces, which helps explain their exquisite sensitivity to human social cues.14

It seems that dogs not only read our facial expressions, they also, in turn, communicate with us using their own facial expressions. Scientists at Portsmouth University’s Dog Cognition Centre in the United Kingdom found that dogs produced far more facial expressions when a human was watching than when a human was not. The expression most commonly used by dogs was one in which they raise their inner brow, making the eyes appear wider and sadder, a look all dog owners will immediately recognize as “puppy dog eyes.”15 Dogs know when we’re watching. And they also know when we’re not. Dogs are more likely to steal food when a person’s eyes are closed or their back is turned.16

YOUR DOG IS WATCHING: NONVERBAL COMMUNICATION AND EMOTIONAL INTELLIGENCE

When we are engaged with our dogs in a training or agility session, they’re watching us very closely to see what it is we are asking them to do. But even when we are not actively working with our dogs, they’re still watching us closely. They may be scanning for clues about what we are going to do next, and research suggests they’re also paying close attention to our emotional state and in some cases modulating their own behavior in response to how we’re feeling.

When we think about training or teaching a dog to live effectively in human environments, we may think that most of our cues are verbal: “Come,” “Sit,” “Stay.” But verbal signals are only one small crucial component of how we communicate with dogs and of how dogs understand us. It is often said that in a human conversation as much as 60 to 90 percent or more of the interaction is nonverbal, depending on the individuals and the context.17 We exchange information through facial expression, body posture, hand gesture, and possibly odors. The same is true for dog-human communication. We may not even be aware of all the nonverbal signals we are giving! On occasion, a dog might tell us what we’re “saying” — for example, that we’re angry — when we don’t even realize what we’re doing.18

How dogs read human nonverbal signals is an area of intense research, and there is much that we still don’t understand well. Some of the questions under investigation include how dogs use human gestures, such as pointing, and whether and why they follow the direction of our gaze.

Following another dog’s gaze is something that some dogs do quite well. Dogs can learn a good deal about what another dog is thinking when they do this, and this simple act may help demonstrate that dogs have a theory of mind — that is, that they know what another dog is thinking and feeling. Research has found that dogs also can follow human gaze, but it isn’t yet clear how consistently they do this. So far, all we can safely say is that some dogs follow human gaze some of the time. Some dogs seem better at following gazes than others, or perhaps they are not “better” but more highly motivated, for whatever reason. But we don’t know why. And we also don’t know what other factors may be at play and what might explain the variation in experimental results. Of course, different dogs are studied in different projects with a variety of researchers, and these variables might underlie differences in research results. Expecting that all dogs will do the same things in the same or similar situations is unrealistic.

The same can be said about variations in the ability of dogs to follow human pointing gestures: Dogs are clearly able to do this, but not all dogs do it all or even some of the time, and the experimental results aren’t straightforward. More research will be needed to really flesh out the details of canine communicative skills.

The one thing we do know for sure is that dogs clearly possess some level of emotional intelligence: They watch us for nonverbal cues, pay attention to our eyes and our hands, and listen to our voices, and from these things they can at times understand us quite well. Emotional intelligence is the capacity to effectively recognize and understand one’s own emotions and the emotions of others and to use this information to guide one’s behavior. This is important as we consider how to interact with our canine companions so as to reduce frustration on both sides. Sometimes we get frustrated when our dogs don’t “listen,” and they likely get frustrated with us when we don’t “speak” clearly or listen to them.

When it comes to dogs following a person’s gaze, we need to pay close attention to the relationship between the dog and the human. In an interesting paper called “DogTube: An Examination of Dogmanship Online,” researchers suggest that “reciprocal attention in the dog-human dyad” is important in gaining a dog’s attention and in handling and training them.19 Further, they write that dogs who “are perceived as difficult to train may be in the hands of people who lack the timing and awareness that characterize good  ogmanship.” The researchers suggest that “dogmanship is reflected in the timeliness of rewards and the ability to acquire and retain a dog’s attention when handling or training them.”

It’s astonishing how skilled dogs are at untangling the complicated signals we send. We expect our dogs to understand us, but our communications are garbled. Most dog owners are “messy” signalers, in that they may give a verbal command without realizing that they are also giving visual signals. We tend to blame it on the dog when they don’t respond in the way we want; we think they are being stupid or stubborn. More likely, we are simply not being clear. One thing we can do to help our dogs is to approach training or teaching with an understanding of how closely dogs pay attention to all our signals, and we can try to align our verbal and nonverbal cues into a consistent and clear message.

Paying closer attention to the nonverbal aspects of training could help many people and dogs work better together. Research conducted by Anna Scandurra and colleagues suggests that gestures are more salient to dogs than verbal cues. For their study, the team trained dogs to identify one of three objects by name and retrieve the object when asked by their owner. Dogs could retrieve each object by a verbal command (“ball”) or by a gesture (owner clearly pointing at ball). When verbal and gestural commands agreed, the dogs moved even more quickly to perform the task. The researchers then had owners give contradictory cues, asking for one object while pointing a finger at another. When verbal and gestural cues were different, most of the dogs followed the gesture.20

Thus, when it comes to our communication with dogs, visual signals, facial expressions, and nonverbal cues may be equally or even more important for dogs than verbal signals.

by Marc Bekoff and Jessica Pierce.

Note

1. Marcello Siniscalchi et al., “Are Dogs Red–Green Colour Blind?” Royal Society Open Science 4 (November 2017), doi: 10.1098/rsos.170869.

2. Horowitz, Being a Dog, 204–5.

3. Ludwig Huber, “How Dogs Perceive and Understand Us,” Current Directions in Psychological Science 25, no. 5 (2016), http://journals.sagepub.com/doi/abs/10.1177/0963721416656329.

4. Bekoff, Canine Confidential. Marc has also noted a relationship between the personality of humans and how permissive they are in allowing their dog to interact with unfamiliar dogs. Namely, outgoing people seem more permissive than introverted people. Of course, these are only informal observations that require more formal study. However, when he has talked with other people at dog parks, they have agreed with this trend.

5. Dominique Autier-Derian et al., “Visual Discrimination of Species in Dogs (Canis familiaris)” Animal Cognition 16, no. 4 (July 2013), https://www.ncbi.nlm.nih.gov/pubmed/23404258.

6. A. Quaranta, M. Siniscalchi, and G. Vallortigara, “Asymmetric Tail-Wagging Responses by Dogs to Different Emotive Stimuli,” Current Biology 17 (2007): R199–R201.

7. Marcello Siniscalchi, Rita Lusito, Giorgio Vallortigara, and Angelo Quaranta, “Seeing Left- or Right-Asymmetric Tail Wagging Produces Different Emotional Responses in Dogs,” Current Biology 23 (2013): 2279–82.

8. Stanley Coren, “Long Tails Versus Short Tails and Canine Communication,” Canine Corner (blog), Psychology Today, February 1, 2012, https://www.psychologytoday.com/blog/canine-corner/201202/long-tails-versus-short-tails-and-canine-communication.

9. See S. D. A. Leaver and T. E. Reimchen, “Behavioural Responses of Canis familiaris to Different Tail Lengths of a Remotely-Controlled Life-Size Dog Replica,” Behaviour 145 (2007): 377–90, http://web.uvic.ca/~reimlab/robodog.pdf.

10. People often wonder why some dogs have floppy ears in the first place, since none of their wild canid relatives do. Here is one interesting hypothesis for why floppy ears may have developed in dogs and other domesticated animals: Adam Cole, “Why Dogs Have Floppy Ears: An Animated Tale,” NPR, January 30, 2018, https://www.npr.org/2018/01/30/580806947/why-dogs-have-floppy-ears-an-animated-tale. The NPR story is based on this study: Adam S. Wilkins, Richard W. Wrangham, and W. Tecumseh Fitch, “The ‘Domestication Syndrome’ in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics,” Genetics 197 (2014): 795–808, http://www.genetics.org/content/197/3/795.

11. Corsin A. Muller et al., “Dogs Can Discriminate Emotional Expressions of Human Faces,” Current Biology 25, no. 5 (February 2015), http://www.cell.com/current-biology/abstract/s0960-9822(14)01693-5.

12. Natalia Albuquerque et al., “Mouth-Licking by Dogs as a Response to Emotional Stimuli,” Behavioural Processes 146 (January 2018), https://www.ncbi.nlm.nih.gov/pubmed/29129727. See also Angelika Firnkes et al., “Appeasement Signals Used by Dogs During Dog-Human Communication,” Journal of Veterinary Behavior 19 (2017): 35–44.

13. Sanni Somppi et al., “Nasal Oxytocin Treatment Biases Dogs’ Visual Attention and Emotional Response toward Positive Human Facial Expressions,” Frontiers in Psychology 8 (2017), https://www.ncbi.nlm.nih.gov/pubmed/29089919.

14. Daniel D. Dilks et al., “Awake fMRI Reveals a Specialized Region in Dog Temporal Cortex for Face Processing,” PeerJ (August 4, 2015), https://peerj.com/articles/1115.

15. Juliane Kaminski et al., “Human Attention Affects Facial Expressions in Domestic Dogs,” Scientific Reports 7 (October 2017): 12914, https://www.ncbi.nlm.nih.gov/pubmed/29051517.

16. J. Call et al., “Domestic Dogs (Canis familiaris) Are Sensitive to the Attentional State of Humans,” Journal of Comparative Psychology 117 (2003): 257–63.

17. Blake Eastman, “How Much of Communication Is Really Nonverbal?” The Nonverbal Group, accessed September 8, 2018, http://www.nonverbalgroup.com/2011/08/how-much-of-communication-is-really-nonverbal. Our point here simply is to note that a good deal of information can be transmitted without words.

18. Marc Bekoff, “Can Dogs Tell Us We’re Angry When We Don’t Know We Are?” Animal Emotions (blog), Psychology Today, November 30, 2017, https://www.psychologytoday.com/blog/animal-emotions/201711/can-dogs-tell-us-were-angry-when-we-dont-know-we-are.

19. Elyssa Payne, Pauleen Bennett, and Paul McGreevy, “DogTube: An Examination of Dogmanship Online,” Journal of Veterinary Behavior 17 (2017): 50–61, http://www.journalvetbehavior.com/article/s1558-7878(16)30167-8/abstract.

20. Anna Scandurra et al., “Should I Fetch One or the Other?: A Study on Dogs on the Object Choice in the Bimodal Contrasting Paradigm,” Animal Cognition 21, no. 1 (November 2017), https://link.springer.com/article/10.1007%2fs10071-017-1145-z.