Let’s say you are standing at a party, or in your office, or on your front lawn. Someone you vaguely know walks up to you. He walks up very close, face-to-face like the Seinfeld close-talker. Close enough that you can see up his nose and smell his breath. He starts a conversation. What do you do?
You will probably have a strong urge to step back. You may or may not do it, depending on the social situation and a host of other factors. But when someone we don’t know well enters our personal space bubble, it can be very uncomfortable.
Everyone has his or her own bubble. In addition to individual preferences, bubbles vary according to age, gender, and culture. And species. The German psychologist David Katz first coined the “bubble” term in 1937. For humans, one of the well-accepted definitions of personal space is from Leslie Hayduk of the University of Western Ontario.
We can define personal space as the area individual humans actively maintain around themselves into which others cannot intrude without arousing discomfort.Hayduk, 1987, p. 118
Dogs have space bubbles, too. As members of a domesticated species, they respond somewhat differently from wild animals. But they are still keenly aware of how close humans, dogs, and other animals are to them and respond accordingly. I am convinced that even when we are on our best behavior, dogs find us to be insensitive clods. Compared to us, they are hyper-alert to movement and body language, and they have been bred for centuries to pay attention to us. Their own language with each other, and to us, is extremely subtle. But we don’t always return the favor. If only we paid attention back!
I wrote the original version of this article in November 2016 for “BARKS in the Guild” after Susan Nilson suggested I expand on what I had written about my dog Zani and how she reacted to pressure. Little did I know the scope of the topic at that time and how much I would learn while investigating it.
In the article I investigate different types of personal space: for humans, dogs, and animals in general. I discuss the types of pressure we put on our dogs. The physical and the gestural. The accidental and deliberate. And the mismatch between the signals of our two species that can result in our being space invaders to dogs.
Animals and Space
I wasn’t stepping out on a limb when I said dogs have space bubbles. Personal space for individuals and groups of animals has been well studied. Different spaces have been defined depending on distance and what happens when the space is entered.
Some of the many terms used for an animal’s immediate personal space have been social force field, personal field, personal sphere, and personal area (McBride, 1971).
But ethologists have defined several other types of space for animals. It can be useful to think of them as concentric ellipses. Here they are from the largest to smallest.
Flight distance (or escape distance) is the distance at which the approach of another animal or human will cause the subject animal to flee. Here are what some eminent scientists have to say about that.
The primary duty of the individual, to ensure its own existence, and thus the preservation of its kind, lies in being prepared to escape. By far the chief occupation of the free wild animal, therefore, is constant watchfulness; eternal alertness for the purpose of avoiding enemies.Hediger, 1955, p. 39
An animal that hopes to keep alive among the dangers of freedom must be constantly on the alert… It is extremely hard to get near them, simply because all animals are so busy keeping an eye open for the possible approach of enemies. As soon as one gets too close, as often happens, they take to flight…. Only when this specific flight distance, which differs for each species, is overstepped by an observed enemy does flight reaction follow; i.e. the animal in a typical manner runs away from it, far enough to put at least its specific escape distance between itself and the enemy once again.Hediger, 1955, p. 40
Dog and wolf experts Raymond and Lorna Coppinger state:
Flight is a hazard avoidance behavior, an essential component of a wild animal’s survival. There are two measurable components to flight distance: 1) how close you can get to the animal before it attempts to flee, and 2) how far away it runs.Coppinger & Coppinger, 2002, p. 64
Fight distance (or critical distance) is the distance at which the subject animal will aggress toward a predator. It is generally closer to the body than flight distance. To most species, humans are responded to as predators.
When animals are cornered, they are unable to observe the flight distance from an approaching man… The animal cannot maintain its personal area free from intrusions by flight, so it must either submit or fight. Hediger named this distance the “fight distance.”McBride, 1971, p. 63
Social distance, on the other hand, is defined inward, toward a group of conspecifics or animals of similar species. It does not involve distance-seeking behavior.
Among animals in groups, social distance was defined by Hediger as “the maximum distance an animal will move away from the group.”McBride, 1971
Inside the social distance, each animal has its personal space, which is defined outwards.
Gregarious animals normally move in a living space between the personal fields of neighbors and social distance.McBride, 1971
For animals and humans, one’s personal space area is larger in front than on the sides. Flight distances are similarly elliptical (McBride & James, 1963). In humans, there is evidence that not only do we respond at a greater distance to the front of a person than to her back, but we actually perceive the person as closer if she is facing us than if she is not (Jung et al., 2016).
Invasion of personal space doesn’t stop at our skin. The ultimate invasion of personal space is bodily harm. In general, a threat is much more dangerous once it has touched, then entered our body, through ingestion or a wound.
Dogs have a delicate sense of this that we appreciate. Mentally healthy dogs who are socialized to humans generally develop bite inhibition with us for play and even when aggressing.
Hediger pointed out that the reduction or elimination of the flight or escape reaction is essential for the successful domestication of a species. That gives us an operationalized definition of domestication.
The artificial removal of the flight distance between animals and man is the result of the process of taming, defined in animal psychology as the disappearance of flight tendency in the presence of man.Hediger, 1955, p. 41
Dogs, as a domesticated species, demonstrate this well. But dogs dwell in a variety of niches in our world. They can be house pets, livestock guardians or other working dogs, village dogs, or completely feral. Their flight distances vary greatly. Also, a dog can already be a tame and happy house pet, but we may work via behavior modification to alter his flight distance because he is overly fearful of various things.
Raymond Coppinger takes the definition of “domestication” one step further:
My argument is that what domesticated—or tame—means is to be able to eat in the presence of human beings. That is the thing that wild wolves can’t do.Public Broadcasting Service, 2007
Proxemics: Personal Space Dynamics for Humans
Space bubbles in humans have been well studied. Proxemics is a subdiscipline of the discipline of non-verbal communication in humans. The term was coined by anthropologist Edward Hall, and refers to the way humans arrange themselves in space in relation to others (when they have a choice). Other fields that involve personal space are cognitive spatial mapping and psychological distance.
Edward Hall (1968) wrote about interactions between humans of different cultures, in fact, observations of these are what prompted him to study proxemics.
Hall identified four zones for human interaction that can be visualized as concentric spheres. From the smallest to the largest, they are the intimate zone, the personal zone, the social/consultive zone, and the public zone. They are largely self-explanatory. Very approximate measurements could be that the intimate zone goes about 2 feet out from the body; the personal zone extends from 2–4 feet; the social/consultive zone extends from 4–12 feet; and the public zone is greater than 12 feet from the individual.
Interpersonal distance is a constellation of sensory inputs that is coded in a particular way. (Hall et al., 1968, p. 94)
Human senses help tell us what is acceptable and safe within each sphere. Kinesthesia helps determine what gestures and touch are permitted. Think of expressions such as “having enough elbow room.” What we hear can affect the zone and we also respond by adjusting our voice level. Olfaction can have strong effects on our desire to be near someone or get away. Can we smell the other person? Are we comfortable with that? Scented body products can modify our responses—in either direction. Our eyes determine whether we are near enough to see what we need to see, and also whether our orientation is appropriate. Movement is sometimes used for escape, and sometimes to approach or optimize.
Hall also identified whether features in space were fixed, semi-fixed, or dynamic. Walls and other structures are fixed. Your dog’s fancy bed in a wooden frame is fixed. But the mats I strew around my house for my dogs to get on are semi-fixed. I move them according to where I need the dogs to be, and the dogs move them, for instance, to pile several into a bed. Interpersonal space is usually dynamic. The space between a human and her dog is dynamic as well. That mutual space moves with us, and our comfort zones (ours and our dogs’) change according to the activity and for many other reasons.
Much of this is unconscious behavior on our parts. For example, when we sit down to have a discussion with someone, we may adjust the position of our chairs. Some of this may have to do with optimizing communication, for instance, being able to see the other’s face better. But threaded through our movements is also a sense of personal space. I may behave differently if I am the host of a meeting, the guest, or if I am with peers in a neutral area. Hall noted large cultural differences not only about optimizing space but also in what situations it was even permissible to move one’s chair:
For example, a German subject (an immigrant to the United States), who treated furniture as fixed, had bolted to the floor the chair on which visitors sat in his office. This caused great consternation among American visitors. One of my Chinese subjects informed me that in China a visitor would not dream of adjusting the furniture to conform to his unwritten definition of an interaction distance unless specifically instructed to do so by his host. American students in my classes, who cover a wide spectrum of ethnic, class, and regional cultures within the United States, have been evenly divided between those who adjust the furniture to conform to an informal norm and those who do not.Hall et al., 1968, p. 91
The Size of Personal Space
Many factors have been identified that affect our arrangements in space vis-à-vis other individuals. Some factors are environmental, such as the space available and noise in the environment.
There is also evidence that modifying our sensory input can influence personal space. One study showed that persons wearing headphones enlarged their own space bubbles (Lloyd, Coates, Knopp, Oram, & Rowbotham, 2009). Conversely, seeing that others were wearing dark glasses or mirror glasses altered the personal space of some research subjects (Yoshida & Hori, 1989).
Fear and anxiety affect personal space. In a study of humans who were afraid of dogs, the auditory signal of a dog growling (as compared to the sound of a sheep bleating) extended the subjects’ personal space (Taffou & Viaud-Delmon, 2014).
For humans, there are countless other variables having to do with personal characteristics. Hayduk (1978) lists the following as potential factors:
- socioeconomic status
- various physical and psychological situations
- attitude similarity
- a history of cooperation
- a stigmatizing condition
- whether the subject is approaching or being approached
- eye contact
- social stimulus intensity
- whether the subject has had assertiveness training
- the intimacy of subjects being discussed
- whether the other person smiles
If we can do so when our personal space is at risk of being infringed, we erect temporary barriers with whatever furniture, possessions, and other objects are available (Fisher & Byrne, 1975).
There is a commonality among all these, and even though they are uniquely human, the common factor is one we share with other animals. Decisions we make regarding our personal space are connected to our safety.
The slightly uncomfortable feeling you get at a public gathering when someone gets too close; the downright creepy feeling you get when a man comes and sits next to you when the rest of the bus or subway car is empty; the fear and panic that floods over you if said guy pulls a knife: these are all on a continuum. The sympathetic nervous system is becoming engaged. Having our space bubbles invaded is not trivial.
There is a reason that humans, dogs, and other animals are wired to be keenly aware of the spaces between them and other individuals. It’s because it can be a matter of survival. Parts of the neurological responses involved in personal space awareness have been identified, and it’s not surprising that the amygdala is involved.
Most of the general public has heard by now that the amygdala is involved in fear responses. But neuroscientist Joseph LeDoux, who has been studying the amygdala for three decades, points out that the amygdala is not the fear center, as it is sometimes described. He considers the amygdala instead as a threat processing center. The brain circuits that control defense responses and those that give rise to feelings of fear interact, but this does not mean they are the same (LeDoux, 2015, p. vii).
LeDoux also points out that humans can be shown pictures of threats in such a way that fear is not triggered, but the amygdala is still activated, and bodily responses result.
It turns out that one of the threats the amygdala is tuned to is the approach of someone or something into our personal space. The amygdala involvement has been determined with a human study, followed by animal research. A woman with complete bilateral damage to her amygdala was found to have no sense of personal space. She reported to examiners that she felt perfectly comfortable at nose-to-nose proximity to one of the researchers with full eye contact. She understood the concept of personal space cognitively and sought to act within societal norms, but had no “sense” of it (Kennedy, Gläscher, Tyszka, & Adolphs, 2009).
Subsequent animal research showed that monkeys with bilateral amygdala lesions stayed closer to humans or other monkeys than monkeys with functional amygdalas. In addition, a preliminary fMRI test of eight healthy humans showed more amygdalar response when the subjects knew the experimenter was standing right next to the fMRI unit than when he was standing farther away (Kennedy, Gläscher, Tyszka, & Adolphs, 2009).
Our sense of personal space is part of our basic wiring.
Recall that the study of proxemics in humans has to do with how humans arrange themselves when they have a choice. But there are certain members of human society to whom we allow less choice. The respecting or entering of space tends to be hierarchical, as Hall (1968) quoted from his Chinese acquaintance. We grant children less space than adults; babies the least of all. Pregnant women are particularly vulnerable to space invasion, such as when perfect strangers touch their abdomens.
Most women have noted, and it has been documented, that men claim more space, even accounting for their larger size. (La France & Mayo, 1979). People with disabilities are often afforded less space (Kilbury, Bordieri, & Wong, 1996).
So this thing we sense so strongly—how close we will stand or sit next to another human—is largely unconscious but is also situational and hierarchical. But what we don’t seem to have is an unconscious respect for a dog’s space, unless the dog is giving out explicitly aggressive signals. If the dog is relaxing or otherwise minding its own business, we assume access.
From Humans to Dogs
In the United States, there is no law against simply entering another’s personal space. However, many crimes involve space invasion, including simple assault, menacing, harassment, battery, and sex crimes. Human rights declarations generally include rights to bodily integrity, individual self-determination, and rights to privacy.
Although considered property under historical law, pets and other animals are gradually gaining more protection and even explicit rights in some countries. But most can’t have complete bodily integrity, self-determination, and privacy because they don’t have the human-like cognition required to understand the consequences of their choices in human culture. We are accustomed to making decisions for them and it’s likely we will always have to do so to some extent. For instance, veterinary surgery and other intrusive procedures are “violations” of a dog’s bodily integrity. We don’t have ways to consult our dogs about their willingness for these.
But I’m arguing for giving them rights when we can. The right to personal space without thoughtless invasion. The right to bodily integrity to the extent possible. Most of us can do a much better job facilitating that for our dogs.
We humans typically don’t respect dogs’ space bubbles to the degree they would probably prefer. Instead, we assume access, taking for granted that they want our petting and touching. Even when we are respectful, our species’ different ways are hard on them. As primates, we express affection by frontal proximity and hugging. For many dogs, this constitutes restraint and invasion. Additionally, as their caregivers, we must sometimes do intrusive things to their bodies or take them to strangers who do so.
Many people even assume access to other people’s dogs. People with fearful and reactive dogs have to go to great measures to prevent intrusion from strangers who see a dog and are driven to pet and touch him. It is becoming more common to at least ask permission of the owner, but few think to check with the dog, or know how to do so.
There is still a common expectation that dogs should automatically like or at least get along with all people and all other dogs. Fearful, shy, or just plain introverted dogs really suffer from this. But even the most extroverted dog still has personal space. We need to learn to respect it.
The Types of Pressure We Put on Dogs
Here are some of the common human behaviors that can easily constitute space invasions. Most result from our differences in size and ways.
- Direct eye contact. (In human proxemics, eye contact is said to narrow the distance between two people and can make an approaching person feel suddenly closer. This appears to be true of dogs and other animals as well.)
- Standing still, facing them straight on.
- Standing tall or leaning over them, especially for small dogs.
- Reaching out with our hands.
- Walking into a dog’s space.
I have a dog who grew up without human contact and she responded with flight to every one of the actions listed above when they came from anyone but me. I worked hard with behavior modification (for her and for me!) to make her more comfortable.
Here are some human behaviors that are even more intrusive and difficult for dogs.
- Crowding too many animals/people in a space that’s not large enough.
- Using molding in training: physically pressing a dog into position.
- Using body pressure in training.
- Confining a dog to a crate or any small space without conditioning.
- Not allowing the dog to withdraw from human interaction.
- Not allowing the dog to hide.
- Keeping a dog who is trying to get away from us on a short leash.
- Holding a dog immobile, whether for management, punishment, or medical procedures.
Many of the above involve two space invasions: restraint, then another procedure. The following is also a twofold invasion.
- Removing an object the dog is guarding.
Resource guarding includes issues of personal space. It is a natural dog behavior that can quickly get a dog in trouble. The dog asserts possession of something, and the assertion typically becomes more aggressive as an intruder gets closer. Many humans are offended at a basic level when a dog takes possession of an item and guards it, even if the dog does not aggress. But whether we are offended or only trying to protect the dog from a dangerous object or situation, there are times we must take things away.
Then we have procedures that actually cause pain. Some are the temporary, sometimes necessary discomfort of veterinary procedures. Note once more that invasion doesn’t always stop at the skin.
- Ear, eye, mouth, and anal exams and treatment.
- Wound dressing.
- Surgical procedures.
Finally, there is the deliberate use of discomfort, pain, or fear in training.
- Training using startling.
- Training using intimidation.
- Training using body pressure.
- Training using pain.
- Training using loud noises.
- Training using flooding: the deliberate restraint of a dog and exposure to something frightening or painful.
Veterinary Visits: A Potential Triple Whammy
As the owner of a formerly feral dog, I have gotten a firsthand look at how a simple veterinary visit can terrify an unsocialized dog. First, she is trapped in a small, enclosed space: the exam room. Second, one or often two strangers enter the room and interact with her. Even experienced vet staff can have a very hard time not making unnecessary intrusions that raise her fear. Attempts at “making friends” that include leaning in, lots of direct eye contact, etc., are scary.
Third, add to that whatever handling of her body is necessary, including intrusive or painful procedures. With my dog, the biggest challenge is the proximity of other humans—it seems to my observation that the handling, even painful types, is less bothersome. Although she is far out from the center of the bell curve, these threats she feels so keenly are potential, albeit milder threats, to a more normally raised dog.
But vet visits are changing, and are becoming so much easier for many dogs. The same year that this article was originally published, the Fear Free Certification for veterinary and other animal professionals was launched. Fear Free Certified professional dog trainer Kate LaSala of Rescued By Training explains, “The Fear Free approach focuses on letting the pet go at their own pace and including the owner in the process as much as possible. This can be the owner feeding while the dog gets examined or other ways of keeping the dog comfortable, sometimes including pre-visit anti-anxiety medications. They also recommend happy visits and only doing what the dog can handle, and have excellent teaching materials on reading dog body language.”
As a dog guardian and a hobby trainer, I have seen the effect of the Fear Free movement, even in some vet practices that aren’t yet certified! More animal professionals in all fields are learning to read body language, and more pet owners are learning how to introduce their young animals to the vet clinic with visits where nothing intrusive happens and nothing goes too fast. There will be little space invasion beyond the minimum of some physical procedures, and even those can be made to be as non-threatening as possible.
Recall Hediger’s definition of domestication as the artificial removal of an animal’s flight response. This gives us a new way to think about what we do in desensitization protocols. As a domesticated species, dogs have a truncated flight response to humans, which results from selective breeding. Even some dogs born feral can quickly gain a positive response to humans (Zimen, 1987). But anyone who works with fearful dogs is still dealing with flight distance; we are seeking to humanely reduce or eliminate their flight distance for specific triggers.
We proceed by getting a trigger within sight and incrementally adjusting distances for exposures accordingly. But keep in mind the different things that can affect flight distance. Angle of approach, speed, and auditory and olfactory information all come into play. My formerly feral dog can walk among pedestrians with a flight distance of virtually zero to her sides and a couple of feet directly in front of her. But she will get alarmed if a person 15 feet away stops, turns, and looks at her for two seconds. The pause, the squared up line of sight, and eye contact instantly enlarge her flight distance. Even if they are 15 feet away, her response is as if the human teleported right up into her face.
Having a dog on leash interferes with the distinction that might otherwise exist between a flight distance and a fight distance. Recall that the fight distance exists when an animal is cornered or restrained, and dogs learn quickly just how much a leash restrains them. So we can’t imagine nice neat concentric ellipses for flight and fight under these circumstances.
We make invasions of dogs’ space that we will never even notice. Dogs, with their keen senses of smell, have a world of sensation we lack. Just as sights and sounds can expand their needed personal space, odors that carry a threat likely can as well. A friend who works with fearful dogs reports that the lingering odor of cigarette smoke brought into the house on a garment triggered escape behavior in one client dog.
Husbandry procedures such as trimming nails, grooming, checking eyes, ears, nose, and mouth can be thought of as exposure protocols as well. Most of these actions are not intrinsically enjoyable for a dog and many are actively unpleasant. Using desensitization and counterconditioning to create positive associations, or at least change the association from unpleasant to neutral, can help a dog cope with these often necessary invasions.
Although dogs seem to comprehend very well that humans are a separate species, they also appear to appreciate any efforts we make to “bridge the gap” and be more sensitive to their personal space.
One of the best instructions I have seen regarding requests to touch dogs in public comes from Madeline Clark Gabriel in her 2011 video, “Dogs Like Kids They Feel Safe With.”
Parents and children need a whole new way to approach dogs. Asking the owner isn’t nearly enough. Children barely wait for an answer before they’re moving in on the dog, and owners often feel pressured to say yes. And nobody is asking the dog.Gabriel, 2011
She suggests that children follow three steps if they want to visit with a dog who is strange to them:
- Step 1: Stop and stand still before asking.
- Step 2: Ask the owner if you can ask the dog: “May I ask your dog if it would like to be petted?”
- Step 3: Invite the dog over with welcoming body language. Do not come towards the dog (Gabriel, 2011).
Although I’m sure there are many dog owners who would be nonplussed by such a request, this is the right direction. Think of how many dogs’ lives would be improved if children and adults asked the dog if he or she wanted to interact—and respected the answer. Also, think of the dog bites it could prevent.
My video, “Does Your Dog REALLY Want To Be Petted” (Anderson, 2012) shows one dog enjoying petting and another one enduring it but not happy about it. It discusses using a consent test—another way to ask the dog—to see if the dog is interested in being touched. In short, the human pets the dog for a few seconds and then stops. If the dog leans in with relaxed body language, and especially if she nudges the human’s hand for more petting, she is probably happy with the touch. The person can continue petting. But if the dog exhibits stress, turns or moves away, or even if she stays in position but is neutral, we can conclude that the petting was not pleasurable to her. In that case, the human should stop the contact.
Many husbandry and medical tasks that must be performed are unpleasant. We and the dogs have no choice about it. Desensitization and counterconditioning and lots of preparation at home can help a dog build resilience for many procedures and for handling in general. And although in our training the dog should always have the right to leave or to say, “wait a minute,” I believe those moments are best used as litmus tests. Repeated and formalized use of escape shouldn’t be a substitute for doing all possible work to create a situation the dog doesn’t want to leave to begin with.
Taking Things Away
We need to practice creating pleasant associations for the dog to our approach when she has food or another object. This will prepare us for the day when we must take something away from the dog for her safety or the safety of another.
We also need to condition any gear we use that is potentially restraining. It is humane for the dog and helpful for the owner if the dog is happy about collars, harnesses, leashes, muzzles, coats, boots, seatbelts, crates, autos, and other enclosures.
Dog Body Language
Most people misunderstand or disregard dogs’ body language. There are thousands of videos on the Internet of dogs who are desperately saying they would prefer that the humans back off, while the humans talk about how happy the dogs are.
If we don’t learn all we can about dog body language, our efforts to not intrude on our dogs’ space and preferences will be in vain. We won’t be able to tell if we are distressing them. So ongoing observation and learning about the dogs we share our lives with, and dogs in general, is crucial.
Perhaps the biggest differences we can make are not the dramatic ones. They may be in the ways we can change our everyday interactions with our dogs. I got interested in this subject because I have a dog, Zani, who is unusually pressure sensitive. She is fairly resilient, but is still very sensitive about her space. To her I am that “looming guy” who stands too close, reaches toward her too abruptly, and makes too much noise.
Whatever I do, I will probably always be “that guy.” But I am learning. I have several strategies. I am proactive about helping my presence be a positive thing for her. I play games with her where she enters my space. I also condition a “happy zone” close around my body.
But I am also learning better doggie manners. I give Zani space in whatever ways I can. I don’t walk straight at her. I use a curved path. In some situations, she prefers not to be looked at, so I don’t. I don’t thrust my hands in her face. I don’t come plop down right beside her. I try to let her initiate necessary approaches at close quarters.
I dedicate this article to Zani.
Copyright 2016 Eileen Anderson
This article was first published in the Pet Professional Guild’s Barks from the Guild in November 2016.
Anderson, E.B. [eileenanddogs]. (2012, August 29). Does Your Dog REALLY Want To Be Petted? [Video file]. Retrieved from https://www.youtube.com/watch?v=-cGDYI-s-cQ.
Coppinger, R., & Coppinger, L. (2002). Dogs: a new understanding of canine origin, behavior and evolution. University of Chicago Press.
Fisher, J.D.; Byrne, D. (1975) “Too close for comfort: Sex differences in response to invasions of personal space.” Journal of Personality and Social Psychology, Vol 32(1), Jul 1975, 15-21.
Gabriel, M.C. [madness2001]. (2011, May 16). Dogs Like Kids They Feel Safe With. [Video file]. Retrieved from https://www.youtube.com/watch?v=vwg9NT_DLZA.
Hall, E. T., Birdwhistell, R. L., Bock, B., Bohannan, P., Diebold Jr, A.R., Durbin, M., Edmonson, M., Fischer, J.L., Hymes, D., Kimball, S., La Barre, W., Lynch, F., McClellan, J.E., Marshall, D.S., Milner, G.B., Sarles, H.B., Trager, G.L., & Vayda, A.P. (1968). Proxemics [and comments and replies]. Current anthropology, 83-108.
Hayduk, L. A. (1978). Personal space: An evaluative and orienting overview. Psychological Bulletin, 85(1), 117-134.
Hediger, H. (1955). Studies of the Psychology and Behavior of Animals in Zoos and Circuses. New York: Criterion.
Hediger, H. (1950). Wild Animals in Captivity. London: Butterworths Scientific Publications.
Jung, E., Takahashi, K., Watanabe, K., de la Rosa, S., Butz, M. V., Bülthoff, H. H., & Meilinger, T. (2016). The Influence of Human Body Orientation on Distance Judgments. Frontiers in psychology, 7. Retrieved from http://journal.frontiersin.org/article/10.3389/fpsyg.2016.00217/full.
Katz, D. (1937). Animals and Men. New York: Longman, Green.
Kennedy, D. P., Gläscher, J., Tyszka, J. M., & Adolphs, R. (2009). Personal space regulation by the human amygdala. Nature neuroscience, 12(10), 1226-1227.
Kilbury, R., Bordieri, J., & Wong, H. (1996). Impact of physical disability and gender on personal space. Journal of Rehabilitation, 62(2), 59-61.
La France, M., & Mayo, C. (1979). A review of nonverbal behaviors of women and men. Western Journal of Communication (includes Communication Reports), 43(2), 96-107.
LeDoux, J. (2015). Anxious: Using the brain to understand and treat fear and anxiety. New York: Penguin.
Lloyd, D. M., Coates, A., Knopp, J., Oram, S., & Rowbotham, S. (2009). Don’t stand so close to me: The effect of auditory input on interpersonal space. Perception, 38(4), 617-620.
McBride, G. (1971). Theories of animal spacing: the role of flight, fight and social distance. Behavior and environment, Springer US, 53-68.
McBride, G., & James, J. W. (1963). Social forces determining spacing and head orientation in a flock of domestic hens. Nature, 197, 1272-1273.
Public Broadcasting Service. (2007) Dogs That Changed the World: What Caused the Domestication of Wolves? Commentary retrieved from http://www.pbs.org/wnet/nature/dogs-that-changed-the-world-what-caused-the-domestication-of-wolves/1276/.[EA2]
Taffou, M., & Viaud-Delmon, I. (2014). Cynophobic fear adaptively extends peri-personal space. Frontiers in psychiatry, 5, 3-9.
Yoshida, F., & Hori, H. (1989). Personal space as a function of eye-contact and spatial arrangements of a group. Shinrigaku kenkyu: The Japanese journal of psychology, 60(1), 53-56.
Zimen, E. (1987). 13. Ontogeny of approach and flight behavior towards humans in wolves, poodles and wolf-poodle hybrids. Man and Wolf: Advances, Issues, and Problems in Captive Wolf Research, 4, 275-292.