We are searching data for your request:
Upon completion, a link will appear to access the found materials.
In the following pictures, the dog seems to be smiling to the camera. People staring at these picture also tend to feel comfortable and relaxed, presumably because they think it's very happy playing with the swing.
However, my question is, is the dog really happy, or we are just (incorrectly) interpreting the dog's facial expression according to our experience used to read humans' facial expression?
I would say no, facial expressions in humans do not generally relate to facial expressions in other animals. Even though there are some cases (as described in the comments an previous answers) that refer to domesticated animals, I do not know of any convincing evidence that the facial expressions of humans are faithfully interpreted, or even mimicked, by other animals - at least outside the group of great apes. Further, the cases arguing that (domesticated) animals can do it are often anecdotal (I am not saying wrong!). Taking an evolutionary perspective, I would not even expect it to be happening (or rather by very close relatives only, i.e. other great apes) because facial expressions as behavioural signals are part of communication and therefore often rather species-specific.
But not only that… there is emerging evidence that facial expressions are not even interpreted uniformly in all human populations: in this article by Crivelli et al. (2016) in Front. Psychol. the authors argue to include anthropological data to cognitive studies. According to their findings, not including a human evolutionary perspective might result in strong biases. They strengthen their point by giving an example of differential interpretation of facial expressions in a Melanesian society which is described in more biological terms in PNAS [Crivelli et al. (2016)]. What they found is that adolescents of this society interpret a facial expression (gasping face) that in other societies conveys fear as a threatening and angry expression.
Generalising this means that if there is divergence in signaling by facial expressions even among human populations, I would consider it unlikely that there is a general homologous system of facial expressions among mammals. There might, however, be a trend in domesticated animals to understand human expressions and adapt behaviour according to them. It still is an extraordinary claim to infer from this that they can actually mimic these expressions, and I have not yet seen convincing evidence for that.
Our cousins in the primate world share the same base facial expressions as we do, happy, sad, disgust, etc; it would make sense that other mammals are capable of facially displaying emotional registers.
However, canines can't pass the mirror test for self awareness, but chimps can. However however, it is known that dogs' oxytocin level rises when they stare into our eyes (similar for female human into her baby's eyes). Thus, if the dog is experiencing elevated feel good neurotransmitters, then a smiling face would appear to make sense.
The question is, have you seen dogs smiling in abused situations?
My other thought on this is that the smile could just be a pavlovian manifestation: you become happy shen the dog smiles, so the dog smiles more--the dog has an association of you being happy to something good happening to it, so it wants to make you happy more.
Sorry I don't have a definite answer for you, but afaik the neuroscience / psychology of dogs keeps expanding in complexity, so I would say that yes, the dog is happy.
Get to know dogs' facial expressions and you will find that there are comparable facial expressions of a canine with that of humans.
Horses Use Complex Facial Expressions Nearly Identical To Humans
The ability to use complex facial expressions to convey emotion isn't unique to humans -- chimpanzees, dogs and cats also possess this ability. Scientists are finding that horses, too, show their feelings on their faces.
In a new study, psychologists from the U.K.'s University of Sussex found that horses use a range of muscular movements to form dynamic facial expressions that are sometimes nearly identical to those of humans.
The researchers compiled a directory of horse facial movements, published online this week in the journal PLOS One, which offers a glimpse into the complex socioemotional lives of horses.
"Horses are undoubtedly emotional animals," Jennifer Wathan, a doctoral researcher at the University of Sussex and one of the study's authors, told The Huffington Post. "But what they feel and how that is expressed is a question that we have yet to pin down."
In a variety of social situations, horses move the muscles in their faces -- largely the muscles around the nostrils, lips and eyes -- to create multiple different expressions that communicate information to other horses.
Wathan and her colleagues devised a comprehensive coding system to better understand common equine facial actions, which they named EquiFACS (Equine Facial Action Coding System). They identified 17 different facial actions -- including "ears forward," "eye white increase," "tongue show" and "lip presser" -- that horses combine to create their expressions.
"Facial expressions are made up of a number of different complicated movements that overlap in a dynamic way," Wathan said. "The Equine Facial Action Coding System gives us a way in which we can make sense of these dynamic and complex forms of communication."
The new research could be put to good use in veterinary settings or in horse training programs. An animator is even using the findings to help create more realistic horse faces, Wathan added.
Inner brow raiser: Horses tend to raise the inner brow of the eye in negative emotional situations as an expression of sadness or fear.
Dogs and humans are known to use a similar action in expressions of surprise, sadness and fear, Wathan noted.
Upper lip raiser: This can be an expression of fear in horses and is often combined with a widening of the eyes, increasing the visibility of the whites of the eyes. Cows also have been shown to display this facial action in stressful situations.
Lip corner puller: This subtle movement is generally a gesture of submission in horses, otherwise known as "snapping." In humans, pulling the corners of the lips is a key component of the smile. The expression is also seen in primates, cats and dogs.
Watch the video below for a demonstration from the researchers:
Experience-based human perception of facial expressions in Barbary macaques ( Macaca sylvanus)
Background: Facial expressions convey key cues of human emotions, and may also be important for interspecies interactions. The universality hypothesis suggests that six basic emotions (anger, disgust, fear, happiness, sadness, and surprise) should be expressed by similar facial expressions in close phylogenetic species such as humans and nonhuman primates. However, some facial expressions have been shown to differ in meaning between humans and nonhuman primates like macaques. This ambiguity in signalling emotion can lead to an increased risk of aggression and injuries for both humans and animals. This raises serious concerns for activities such as wildlife tourism where humans closely interact with wild animals. Understanding what factors (i.e., experience and type of emotion) affect ability to recognise emotional state of nonhuman primates, based on their facial expressions, can enable us to test the validity of the universality hypothesis, as well as reduce the risk of aggression and potential injuries in wildlife tourism.
Methods: The present study investigated whether different levels of experience of Barbary macaques, Macaca sylvanus, affect the ability to correctly assess different facial expressions related to aggressive, distressed, friendly or neutral states, using an online questionnaire. Participants' level of experience was defined as either: (1) naïve: never worked with nonhuman primates and never or rarely encountered live Barbary macaques (2) exposed: shown pictures of the different Barbary macaques' facial expressions along with the description and the corresponding emotion prior to undertaking the questionnaire (3) expert: worked with Barbary macaques for at least two months.
Results: Experience with Barbary macaques was associated with better performance in judging their emotional state. Simple exposure to pictures of macaques' facial expressions improved the ability of inexperienced participants to better discriminate neutral and distressed faces, and a trend was found for aggressive faces. However, these participants, even when previously exposed to pictures, had difficulties in recognising aggressive, distressed and friendly faces above chance level.
Discussion: These results do not support the universality hypothesis as exposed and naïve participants had difficulties in correctly identifying aggressive, distressed and friendly faces. Exposure to facial expressions improved their correct recognition. In addition, the findings suggest that providing simple exposure to 2D pictures (for example, information signs explaining animals' facial signalling in zoos or animal parks) is not a sufficient educational tool to reduce tourists' misinterpretations of macaque emotion. Additional measures, such as keeping a safe distance between tourists and wild animals, as well as reinforcing learning via videos or supervised visits led by expert guides, could reduce such issues and improve both animal welfare and tourist experience.
Keywords: Ethnoprimatology Facial expressions Human-macaque interactions Primates Tourism Universal hypothesis.
You Won’t Believe What Animal Has More Facial Expressions Than Dogs And Chimpanzees
Humans lead the pack in the animal kingdom in terms of distinct facial expressions, while chimpanzees also display a variety of facial movements. Dog owners can attest to the emotional expressions of canines, but a study in Great Britain notes that one animal in particular has more facial expressions than previously thought.Horses Smile, Raise Inner Eyebrows
Horses have 17 separate facial expressions, as determined by a scientific program called Facial Action Coding Systems, the second-most of any animals studied to date. By comparison, humans have 27, chimps have 13 and dogs have 16. Surprisingly, horses and humans actually make similar facial gestures, including smiling and raising eyebrows, according to Time.
Horses raise their lips to expose teeth in a smile-like gesture. They also raise their inner eyebrows to make a horse's eyes appear bigger, in a “puppy-dog eyes” expression. Horses combine many elements on their upper faces, such as eyes and ears, to create facial expressions near the eyes, notes PLOS One. Muscles can twitch the ears and open the eyes wide enough to show the whites of their eyes. Horses don't have whites around the front parts of their eyes, but they do in the back. When a horse shows the whites in its eyes, that may indicate fear, in a manner similar to humans and other animals.
Another expression similar to humans is the upper lip curl that exposes the upper teeth. This movement also curls the nostrils in horses, much like it does in humans. In terms of an emotional expression, humans use this to show disdain. Horses have different levels of upper lip curls that may be either minor and quick, or major and longer in duration.
This video shows several facial expressions of horses. One of the first is when this huge animal looks behind as it's being groomed. Another expression is a yawn, which may indicate pain or confusion. A horse may nuzzle a brush with its nose and mouth to explore it, and some horse handlers allow horses to see and sense horse tack before the owner puts anything on the animal's back. In theory, this makes the horse more comfortable with any tools and equipment. Facial expressions in horses do more than just serve as sensory devices to explore the physical world around the animals.
Our Featured Programs
See how we’re making a difference for People, Pets, and the Planet and how you can get involved!
Why Horses Have Facial Expressions
Scientists already know that horses have complex social structures within a herd and among equine relatives. Discovery News states facial expressions help horses communicate with each other more effectively. As such, if humans can tie distinct facial expressions of a horse to a particular emotion within the animal's brain, reading their face can lead to a better understanding of horses in general.Horses and humans already understand each other to some extent, as they work closely together on ranches and farms. Notice how this horse feels after passing gas, similar to the way humans do after getting some intestinal relief.
Help Rescue Animals
Provide food and vital supplies to shelter pets at The Animal Rescue Site for free! &rarr
Help Rescue Animals
Provide food and vital supplies to shelter pets at The Animal Rescue Site for free! &rarr
Dogs know that smile on your face
Dogs can tell the difference between happy and angry human faces, according to a new study in the Cell Press journal Current Biology on February 12. The discovery represents the first solid evidence that an animal other than humans can discriminate between emotional expressions in another species, the researchers say.
"We think the dogs in our study could have solved the task only by applying their knowledge of emotional expressions in humans to the unfamiliar pictures we presented to them," says Corsin Müller of the University of Veterinary Medicine Vienna.
Previous attempts had been made to test whether dogs could discriminate between human emotional expressions, but none of them had been completely convincing. In the new study, the researchers trained dogs to discriminate between images of the same person making either a happy or an angry face. In every case, the dogs were shown only the upper or the lower half of the face. After training on 15 picture pairs, the dogs' discriminatory abilities were tested in four types of trials, including
(1) the same half of the faces as in the training but of novel faces,
(2) the other half of the faces used in training,
(3) the other half of novel faces, and
(4) the left half of the faces used in training.
The dogs were able to select the angry or happy face more often than would be expected by random chance in every case, the study found. The findings show that not only could the dogs learn to identify facial expressions, but they were also able to transfer what they learned in training to new cues.
"Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings, and they can do this not only for people they know well, but even for faces they have never seen before," says Ludwig Huber, senior author and head of the group at the University of Veterinary Medicine Vienna's Messerli Research Institute.
What exactly those different meanings are for the dogs is hard to say, he adds, "but it appears likely to us that the dogs associate a smiling face with a positive meaning and an angry facial expression with a negative meaning." Müller and Huber report that the dogs were slower to learn to associate an angry face with a reward, suggesting that they already had an idea based on prior experience that it's best to stay away from people when they look angry.
The researchers will continue to explore the role of experience in the dogs' abilities to recognize human emotions. They also plan to study how dogs themselves express emotions and how their emotions are influenced by the emotions of their owners or other humans.
"We expect to gain important insights into the extraordinary bond between humans and one of their favorite pets, and into the emotional lives of animals in general," Müller says.
Horses Smile and Pout Just Like Humans, Study Says
H orse faces share some surprising similarities to human faces, shows a curious new study published in the journal PLOS ONE.
After dissecting a horse head, analyzing its musculature, and scrutinizing 15 hours of horse video footage, a group of researchers managed to map out every possible facial expression a horse could make. It turns out our faces are a lot more similar than we think.
&ldquoHorses and humans are distantly related and have such differently shaped faces that I personally thought there would be really no similarities,&rdquo says study author Jennifer Wathan, a PhD candidate in social cognition and communication in horses at the University of Sussex in the U.K. &ldquoBut there was a surprising amount of similarities.&rdquo
For the first time, Wathan and her colleagues created a full map of a horse face using a technique called the Facial Action Coding Systems (FACS). It&rsquos a tool for objectively measuring facial movement, without letting subjective interpretations of facial expressions get in the way.
Humans have a FACS (we make 27 separate facial movements), and so do chimpanzees (they make 13) and dogs (16 for them). But horses had even more: 17 facial movements in total. &ldquoMost people who have horses know they are expressive and use their ears a lot, but I&rsquove got to admit, I was really surprised by the extent to which they use their face,&rdquo Wathan says. &ldquoThey&rsquove got a huge facial repertoire.&rdquo
It&rsquos not yet clear why there are similarities between humans and horses. &ldquoWhether animals communicate intentionally is still a huge and fairly contested issue,&rdquo she says. But three of our shared expressions particularly captivated Wathan. &ldquoOne is raising the inner eyebrows,&rdquo she says&mdashsomething humans do when we&rsquore scared, surprised or sad. &ldquoYou know, puppy-dog eyes,&rdquoshe says. (Dogs really do this, by the way: one study of shelter dogs, by Bridget Waller and Juliane Kaminski at the University of Portsmouth, found that dogs who raised their brows were adopted faster than dogs who didn&rsquot. You can see what it looks like by watching this video that the researchers made to go with their study:)
&ldquoThey think that&rsquos potentially because it enhances the proportions of the dog&rsquos face to make them look more like human babies,&rdquo Wathan says. &ldquoIt taps into our sensory biases to provide care for human babies.&rdquo Horses also do this expression, she says, &ldquoand it seems that they do it in negative emotional situations, too.&rdquo
Humans also pull the corners of their lips back&mdashalso known as smiling&mdashsort of like horses do. &ldquoIt seems to be part of the submissive gesture,&rdquo she says, and younger horses tend to do it to older horses.
Finally, both humans and horses widen their eyes in fear.
Findings like these can help us understand the evolution of complex communication between species&mdashand they may suggest that using complex facial expressions to communicate is an ancient ability we shared with our last common ancestor with horses, or that the ability has evolved under the social pressure to communicate with important social partners, Wathan says.” Horses, like us, have a rich social life where effective communication would be to their advantage, she says.
“The ability to use complex facial expressions was one of these things that was kind of touted as being uniquely human,” Wathan says. “But other species are doing it, and we share these abilities with all the other species around us.”
Horses understand human facial expressions
Like fearful humans, horses raise the inner brow of their eyes when threatened or surprised. Altogether their faces can convey 17 emotions (ours express 27), and they readily recognize the expressions on their fellow equines. But can they read our facial cues? To find out, researchers tested 28 horses, including 21 geldings and seven mares, from stables in the United Kingdom. Each horse was led by his/her halter rope to a position in the stable, and then presented with a life-size color photograph of the face of a man. The man was either smiling or frowning angrily. The scientists recorded the animals’ reactions, and measured their heart rates. Other studies have shown that stressed horses’ heart rates fluctuate, and when the horses looked at the angry man, their hearts reached a maximum heart rate more quickly than when they viewed the smiling image. When shown the angry face, 20 of the horses also turned their heads so that they could look at it with their left eye—a response that suggests they understood the expression, the scientists report online today in Biology Letters, because the right hemisphere of the brain is specialized for processing negative emotions. Dogs, too, have this “left-gaze bias” when confronting angry faces. Also, like dogs, the horses showed no such bias, such as moving their heads to look with the right eye, when viewing the happy faces—perhaps because the animals don’t need to respond to nonthreatening cues. But an angry expression carries a warning—the person may be about to strike. The discovery that horses as well as dogs—the only two animals this has been tested in—can read our facial expressions spontaneously and without training suggests one of two things: Either these domesticated species devote a lot of time to learning our facial cues, or the ability is innate and more widespread in the animal kingdom than previously thought.
Dogs have pet facial expressions to use on humans, study finds
Dogs really do turn on the puppy eyes when humans look at them, according to researchers studying canine facial expressions.
Scientists have discovered that dogs produce more facial movements when a human is paying attention to them – including raising their eyebrows, making their eyes appear bigger – than when they are being ignored or presented with a tasty morsel.
The research pushes back against the belief that animal facial expressions are largely unconscious movements, that reflect internal sentiments, rather than a way to communicate.
“Facial expression is often seen as something that is very emotionally driven and is very fixed, and so it isn’t something that animals can change depending on their circumstances,” said Bridget Waller, professor of evolutionary psychology at the University of Portsmouth, and an author of the study.
The research joins a number of studies probing the extraordinary relationship between humans and their canine companions, including work suggesting dogs understand both the words and the tone of human speech.
Published in the journal Scientific Reports, the study involved researchers using a video camera to record the facial movements of 24 dogs over a series of experiments in which a human either faced the animal, or faced away, and presented the dog with a tidbit, or did not.
The recordings were then examined by the team frame by frame to determine changes in the facial muscles of the canines.
The results reveal that the pooches produced far more facial expressions when the human was facing the dog, than when they turned away – in particular, the animals were more likely to show their tongues and raise their inner eyebrows.
In 1872 Charles Darwin published a book titled The Expression of the Emotions in Man and Animals in which he declared that humans evolved facial and emotional expression from animal ancestors. Darwin believed not only that facial expressions are similar between man and beast, but also that they convey similar emotions. Yet while animals in general are capable of some basic expressions, such as fear and aggression, none (including apes and monkeys) show anything comparable to the range and nuance of human facial expression. For example, it is often quite easy to tell from facial expressions if a human is lying, cheating, embarrassed or insincere, but these subtleties of expression are entirely lacking in animals.
Humans are capable of expressing about 20 different facial expressions. These expressions convey specific meanings to other people much like a spoken language. But just as in verbal languages, we can lie or deceive with our facial expression. Consider an insincere smile—it’s a smile but something isn’t right. What is it that tips us off?
Fake smiles use only certain muscles going to the corners of the mouth, while real smiles involve many facial muscles, including those around our eyes. One can even be trained to discern if someone is hiding their real emotions by masking facial expression. Studies have shown that trained observers can recognize concealed emotions by detecting “micro expressions” lasting for about only a quarter second.
Published by the Royal Society. All rights reserved.
. 2001 Human expressions as adaptations: evolutionary questions in facial expression research . Am. J. Phys. Anthropol . 33, 3–24. (doi:10.1002/ajpa.20001) Crossref, PubMed, ISI, Google Scholar
Parr LA, Winslow JT, Hopkins WD, de Waal FBM
. 2000 Recognizing facial cues: individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta) . J. Comp. Psychol . 114, 47–60. (doi:10.1037/0735-7036.114.1.47) Crossref, PubMed, ISI, Google Scholar
. 2007 Integrating face and voice in person perception . Trends Cogn. Sci . 11, 535–543. (doi:10.1016/j.tics.2007.10.001) Crossref, PubMed, ISI, Google Scholar
Yuval-Greenberg S, Deouell LY
. 2009 The dog's meow: asymmetrical interaction in cross-modal object recognition . Exp. Brain Res . 193, 603–614. (doi:10.1007/s00221-008-1664-6) Crossref, PubMed, ISI, Google Scholar
Ghazanfar AA, Logothetis NK
. 2003 Facial expressions linked to monkey calls . Nature 423, 937–938. (doi:10.1038/423937a) Crossref, PubMed, ISI, Google Scholar
. 2004 Matching vocalizations to vocalizing faces in a chimpanzee (Pan troglodytes) . Anim. Cogn . 7, 179–184. (doi:10.1007/s10071-004-0212-4) Crossref, PubMed, ISI, Google Scholar
. 2013 Crossmodal integration of conspecific vocalizations in rhesus macaques . PLoS ONE 8, e81825. (doi:10.1371/journal.pone.0081825) Crossref, PubMed, ISI, Google Scholar
Nagasawa M, Mitsui S, En S, Ohtani N, Ohta M, Sakuma Y, Onaka T, Mogi K, Kikusui T
. 2015 Oxytocin-gaze positive loop and the coevolution of human-dog bonds . Science 348, 333–336. (doi:10.1126/science.1261022) Crossref, PubMed, ISI, Google Scholar
Faragó T, Pongrácz P, Range F, Virányi Z, Miklósi A
. 2010 ‘The bone is mine’: affective and referential aspects of dog growls . Anim. Behav . 79, 917–925. (doi:10.1016/j.anbehav.2010.01.005) Crossref, ISI, Google Scholar
Taylor AM, Reby D, McComb K
. 2011 Cross modal perception of body size in domestic dogs (Canis familiaris) . PLoS ONE 6, e0017069. (doi:10.1371/journal.pone.0017069) Crossref, ISI, Google Scholar
Nagasawa M, Murai K, Mogi K, Kikusui T
. 2011 Dogs can discriminate human smiling faces from blank expressions . Anim. Cogn . 14, 525–533. (doi:10.1007/s10071-011-0386-5) Crossref, PubMed, ISI, Google Scholar
Racca A, Guo K, Meints K, Mills DS
. 2012 Reading faces: differential lateral gaze bias in processing canine and human facial expressions in dogs and 4-year-old children . PLoS ONE 7, e36076. (doi:10.1371/journal.pone.0036076) Crossref, PubMed, ISI, Google Scholar
Müller CA, Schmitt K, Barber ALA, Huber L
. 2015 Dogs can discriminate emotional expressions of human faces . Curr. Biol . 25, 601–605. (doi:10.1016/j.cub.2014.12.055) Crossref, PubMed, ISI, Google Scholar
. 2013 Can domestic dogs (Canis familiaris) use referential emotional expressions to locate hidden food? Anim. Cogn . 16, 137–145. (doi:10.1007/s10071-012-0560-4) Crossref, PubMed, ISI, Google Scholar
. In press. Does affective information influence domestic dogs’ (Canis lupus familiaris) point-following behavior? Anim . Cogn. (doi:10.1007/s10071-015-0934-5) ISI, Google Scholar
Fukuzawa M, Mills DS, Cooper JJ
. 2005 The effect of human command phonetic characteristics on auditory cognition in dogs (Canis familiaris) . J. Comp. Psychol . 119, 117–120. (doi:10.1037/0735-7036.119.1.117) Crossref, PubMed, ISI, Google Scholar
. 2012 Empathic-like responding by domestic dogs (Canis familiaris) to distress in humans: an exploratory study . Anim. Cogn . 15, 851–859. (doi:10.1007/s10071-012-0510-1) Crossref, PubMed, ISI, Google Scholar
Andics A, Gácsi M, Faragó T, Kis A, Miklósi A
. 2014 Voice-sensitive regions in the dog and human brain are revealed by comparative fMRI . Curr. Biol . 24, 574–578. (doi:10.1016/j.cub.2014.01.058) Crossref, PubMed, ISI, Google Scholar
Kondo N, Izawa E-I, Watanabe S
. 2012 Crows cross-modally recognize group member but not non-group members . Proc. R. Soc. B 279, 1937–1942. (doi:10.1098/rspb.2011.2419) Link, ISI, Google Scholar
Silwa J, Duhamel J, Pascalis O, Wirth S
. 2011 Spontaneous voice–face identity matching by rhesus monkeys for familiar conspecifics and humans . Proc. Natl Acad. Sci. USA 108, 1735–1740. (doi:10.1073/pnas.1008169108) Crossref, PubMed, ISI, Google Scholar
. 2009 Cross-modal individual recognition in domestic horses (Equus caballus) . Proc. Natl Acad. Sci. USA 106, 947–951. (doi:10.1073/pnas.0809127105) Crossref, PubMed, ISI, Google Scholar
. 2012 Cross-modal individual recognition in domestic horses (Equus caballus) extends to familiar humans . Proc. R. Soc. B 282, 3131–3138. (doi:10.1098/rspb.2012.0626) Link, ISI, Google Scholar
Somppi S, Törnqvist H, Hänninen L, Krause C, Vainio O
. 2014 How dogs scan familiar and inverted faces: an eye movement study . Anim. Cogn . 17, 793–803. (doi:10.1007/s10071-013-0713-0) Crossref, PubMed, ISI, Google Scholar
Guo K, Meints K, Hall C, Hall S, Mills D
. 2009 Left gaze bias in humans, rhesus monkeys and domestic dogs . Anim. Cogn . 12, 409–418. (doi:10.1007/s10071-008-0199-3) Crossref, PubMed, ISI, Google Scholar
Holden E, Calvo G, Collins M, Bell A, Reid J, Scot EM, Nolan AM
. 2014 Evaluation of facial expression in acute pain in cats . J. Small Anim. Pract . 55, 615–621. (doi:10.1111/jsap.12283) Crossref, PubMed, ISI, Google Scholar