Dog behavior

Dogs roughhousing

A drawing by Konrad Lorenz showing facial expressions of a dog - a communication behavior

Dog behavior is the internally coordinated responses (actions or inactions) of the domestic dog (individuals or groups) to internal and/or external stimuli. As the oldest domesticated animal species, with estimates ranging from 9,000–30,000 years BCE, the behavior of dogs has inevitably have been shaped by millennia of contact with humans. As a result of this physical and social evolution, dogs, more than any other species, have acquired the ability to understand and communicate with humans and they are uniquely attuned to our behaviors. Behavioral scientists have uncovered a surprising set of social-cognitive abilities in the domestic dog. These abilities are not expressed by the dog's closest canine relatives nor by other mammals such as great apes. Rather, these skills parallel some of the social-cognitive skills of human children.

Evolution/Domestication/Co-evolution with humans

Main article: Origin of the domestic dog

The origin of the domestic dog (Canis lupus familiaris or Canis familiaris) is not clear. Whole genome sequencing indicates that the dog, the gray wolf and the extinct Taymyr wolf diverged at around the same time 27,000-40,000 years ago. How dogs became domesticated is not clear, however the two main hypothesis are self-domestication or human domestication. There exists evidence of human-canine coevolution.

Intelligence

Further information: Dog intelligence

Dog intelligence is the ability of the dog to perceive information and retain it as knowledge for applying to solve problems. Dogs have been shown to learn by inference. A study with Rico showed that he knew the labels of over 200 different items. He inferred the names of novel items by exclusion learning and correctly retrieved those novel items immediately and also 4 weeks after the initial exposure. Dogs have advanced memory skills. A study documented the learning and memory capabilities of a border collie, "Chaser", who had learned the names and could associate by verbal command over 1,000 words. Dogs are able to read and react appropriately to human body language such as gesturing and pointing, and to understand human voice commands. After undergoing training to solve a simple manipulation task, dogs that are faced with an insoluble version of the same problem look at the human, while socialized wolves do not. Dogs demonstrate a theory of mind by engaging in deception.

Senses

Further information: Dog anatomy#Senses

The dog's senses include vision, hearing, sense of smell, taste, touch and sensitivity to the earth's magnetic field.

Communication behavior

Further information: Dog communication

Dog communication is about how dogs "speak" to each other, how they understand messages that humans send to them, and how humans can translate the ideas that dogs are trying to transmit. These communication behaviors include eye gaze, facial expression, vocalization, body posture (including movements of bodies and limbs) and gustatory communication (scents, pheromones and taste). Humans communicate with dogs by using vocalization, hand signals and body posture.

Social behavior

Play

Dog-dog

Dog playing with a guinea pig.

Play between dogs usually involves several behaviours that are often seen in aggressive encounters, for example, nipping, biting and growling. It is therefore important for the dogs to place these behaviours in the context of play, rather than aggression. Dogs signal their intent to play with a range of behaviours including a "play-bow", "face-paw" "open-mouthed play face" and postures inviting the other dog to chase the initiator. Similar signals are given throughout the play bout to maintain the context of the potentially aggressive activities.

From a young age, dogs engage in play with one another. Dog play is made up primarily of mock fights. It is believed that this behavior, which is most common in puppies, is training for important behaviors later in life. Play between puppies is not necessarily a 50:50 symmetry of dominant and submissive roles between the individuals; dogs who engage in greater rates of dominant behaviours (e.g. chasing, forcing partners down) at later ages also initiate play at higher rates. This could imply that winning during play becomes more important as puppies mature.

Dog-human

The motivation for a dog to play with another dog is distinct from that of a dog playing with a human. Dogs walked together with opportunities to play with one another, play with their owners with the same frequency as dogs being walked alone. Dogs in households with two or more dogs play more often with their owners than dogs in households with a single dog, indicating the motivation to play with other dogs does not substitute for the motivation to play with humans.

It is a common misconception that winning and losing games such as "tug-of-war" and "rough-and-tumble" can influence a dog's dominance relationship with humans. Rather, the way in which dogs play indicates their temperament and relationship with their owner. Dogs that play rough-and-tumble are more amenable and show lower separation anxiety than dogs which play other types of games, and dogs playing tug-of-war and "fetch" are more confident. Dogs which start the majority of games are less amenable and more likely to be aggressive.

Playing with humans can affect the cortisol levels of dogs. In one study, the cortisol responses of police dogs and border guard dogs was assessed after playing with their handlers. The cortisol concentrations of the police dogs increased, whereas the border guard dogs' hormone levels decreased. The researchers noted that during the play sessions, police officers were disciplining their dogs, whereas the border guards were truly playing with them, i.e. this included bonding and affectionate behaviours. They commented that several studies have shown that behaviours associated with control, authority or aggression increase cortisol, whereas play and affiliative behaviour decrease cortisol levels.

Empathy

In 2012, a study found that dogs oriented toward their owner or a stranger more often when the person was pretending to cry than when they were talking or humming. When the stranger pretended to cry, rather than approaching their usual source of comfort, their owner, dogs sniffed, nuzzled and licked the stranger instead. The dogs’ pattern of response was behaviorally consistent with an expression of empathic concern.

A study found a third of dogs suffered from anxiety when separated from others.

Personalities

The term personality has been applied to human research, whereas the term temperament has been mostly used for animal research. However, both terms have been used interchangeably in the literature, or purely to distinguished humans for animals and avoid anthropomorphism. Personality can be defined by “a set of behaviours that are consistent over context and time”. Human personality is often studied using models that look at broad dimensions of personality. For example, the Five Factor Model is one of the most commonly used model, and the most extensively studied. It is composed of five dimensions: openness, conscientiousness, extraversion, agreeableness, and neuroticism. Studies of dog personality have also tried to identify the presence of broad personality traits that are stable over time. Recently, dog’s personality dimension has been shown to be relatively consistent over time.

There are different approaches to assess dog personality:

• Ratings of individual dogs: either a caretaker or a dog expert who is familiar with the dog is asked to answer a questionnaire, for instance the Canine Behavioural Assessment and Research Questionnaire, concerning how often the dog show certain type of behaviour.
• Test batteries: the dog is submitted to a set of test and its reactions are evaluated on a behavioural scale. For instance, the dog is presented to a familiar and then an unfamiliar person :in order to measure sociability or aggression.
• Observational test: The dog’s behaviour is evaluated in a selected but not controlled environment. An observer focus on the dog’s reactions to naturally occurring stimuli. For example a :walk through the supermarket can allow the observer to see the dog in various types of conditions (crowd, loud noise …).

Several potential personality traits have been identified in dogs, for instance "Playfulness", "Curiosity/Fearlessness, "Chase-proneness", "Sociability and Aggressiveness" and "Shyness–Boldness". A meta-analysis of 51 published peered review articles identified seven dimension of canine personality:

1. Reactivity (approach or avoidance of new objects, increased activity in novel situations)
2. Fearfulness (shaking, avoiding novel situations)
3. Activity
4. Sociability (initiating friendly interactions with people and other dogs)
5. Responsiveness to Training (working with people, learning quickly)
6. Submissiveness
7. Aggression

Dog Breed plays an important role in the dog’s personality dimensions, while the effects of age and sex have not been clearly determined. Dogs personality models can be used for a range of tasks, including guide and working dog selection, finding appropriate families to re-home shelter dogs, or selecting breeding stock.

Leadership, dominance and social groups

Two dogs playing follow the leader.

Dominance is a descriptive term for the relationships between pairs of individuals. Among ethologists, dominance has been defined as ‘‘an attribute of the pattern of repeated, agonistic interactions between two individuals, characterized by a consistent outcome in favor of the same dyad member and a default yielding response of its opponent rather than escalation. The status of the consistent winner is dominant and that of the loser subordinate.’’ Another definition is that a dominant animal has priority of access to resources. Dominance is a relative attribute, not absolute; there is no reason to assume that a high-ranking individual in one group would also become high ranking if moved to another. Nor is there any good evidence that ‘‘dominance’’ is a lifelong character trait. Competitive behavior characterized by confident (e.g. growl, inhibited bite, stand over, stare at, chase, bark at) and submissive (e.g. crouch, avoid, displacement lick/yawn, run away) patterns exchanged.

One test to ascertain which in a group was the dominant dog used the following criteria: When a stranger comes to the house, which dog starts to bark first or if they start to bark together, which dog barks more or longer? Which dog licks more often the other dog’s mouth? If the dogs get food at the same time and at the same spot, which dog starts to eat first or eats the other dog’s food? If the dogs start to fight, which dog wins usually?

Domestic dogs appear to pay little attention to relative size, despite the large weight differences between the largest and smallest individuals; for example, size was not a predictor of the outcome of encounters between dogs meeting while being exercised by their owners nor was size correlated with neutered male dogs. Therefore, many dogs do not appear to pay much attention to the actual fighting ability of their opponent, presumably allowing differences in motivation (how much the dog values the resource) and perceived motivation (what the behavior of the other dog signifies about the likelihood that it will escalate) to play a much greater role.

Two dogs that are contesting possession of a highly valued resource for the first time, if one is in a state of emotional arousal, or if one is in pain, or if reactivity is influenced by recent endocrine changes or motivational states such as hunger, then the outcome of the interaction may be different than if none of these factors were present. Equally, the threshold at which aggression is shown may be influenced by a range of medical factors, or, in some cases, precipitated entirely by pathological disorders. Hence, the contextual and physiological factors present when 2 dogs first encounter each other may profoundly influence the long-term nature of the relationship between those dogs. The complexity of the factors involved in this type of learning means that dogs may develop different ‘‘expectations’’ about the likely response of another individual for each resource in a range of different situations. Puppies learn early not to challenge an older dog and this respect stays with them into adulthood. When adult animals meet for the first time, they have no expectations of the behavior of the other: they will both, therefore, be initially anxious and vigilant in this encounter (characterized by the tense body posture and sudden movements typically seen when 2 dogs first meet), until they start to be able to predict the responses of the other individual. The outcome of these early adult–adult interactions will be influenced by the specific factors present at the time of the initial encounters. As well as contextual and physiological factors, the previous experiences of each member of the dyad of other dogs will also influence their behavior.

Scent

Dogs have an olfactory sense 40 times more sensitive than a human's and they commence their lives operating almost exclusively on smell and touch. The special scents that dogs use for communication are called pheromones. Different hormones are secreted when a dog is angry, fearful or confident, and some chemical signatures identify the sex and age of the dog, and if a female is in the estrus cycle, pregnant or recently given birth. Many of the pheromone chemicals can be found dissolved in a dog's urine, and sniffing where another dog has urinated gives the dog a great deal of information about that dog. Male dogs prefer to mark vertical surfaces and having the scent higher allows the air to carry it further. The height of the marking tells other dogs about the size of the dog, as among canines size is an important factor in dominance.

Dogs (and wolves) not only use urine but also their stools to mark their territories. The anal gland of canines give a particular signature to fecal deposits and identifies the marker as well as the place where the dung is left. Dogs are very particular about these landmarks, and engage in what is to humans a meaningless and complex ritual before defecating. Most dogs start with a careful bout of sniffing of a location, perhaps to erect an exact line or boundary between their territory and another dog's territory. This behavior may also involve a small degree of elevation, such as a rock or fallen branch, to aid scent dispersal. Scratching the ground after defecating is a visual sign pointing to the scent marking. The freshness of the scent gives visitors some idea of the current status of a piece of territory and if it is used frequently. Regions under dispute, or used by different animals at different times, may lead to marking battles with every scent marked-over by a new competitor.

Further information: Dog communication

Feral dogs

Feral dogs are those dogs living in a wild state with no food and shelter intentionally provided by humans, and showing a continuous and strong avoidance of direct human contacts. In the developing world pet dogs are uncommon, but feral, village or community dogs are plentiful around humans. The distinction between feral, stray, and free ranging dogs is sometimes a matter of degree, and a dog may shift its status throughout its life. In some unlikely but observed cases, a feral dog that was not born wild but living with a feral group can become rehabilitated to a domestic dog with an owner. A dog can become a stray when it escapes human control, by abandonment or being born to a stray mother. A stray dog can become feral when forced out of the human environment or when co-opted or socially accepted by a nearby feral group. Feralization occurs through the development of a fear response to humans.

Feral dogs are not reproductively self-sustaining, suffer from high rates of juvenile mortality, and depend indirectly on humans for their food, their space, and the supply of co-optable individuals.

See further: behavior compared to other canids.

Other behavior

Dogs have a general behavioral trait of strongly preferring novelty ("neophillia") compared to familiarity. The average sleep time of a dog in captivity in a 24-hour period is 10.1 hours.

Reproduction behavior

Further information: Canine reproduction

Estrous cycle and mating

Although puppies do not have the urge to procreate, males sometimes engage in sexual play in the form of mounting, as early as 5 weeks-of-age.

Dogs reach sexual maturity and can reproduce during their first year, in contrast to wolves at two years-of-age. Bitches have their first estrus ("heat") at 6 to 12 months-of-age; smaller dogs tend to come into heat earlier whereas larger dogs take longer to mature.

Dog bitches have an estrous cycle that is nonseasonal and monestrus, i.e. there is only one estrus per estrous cycle. The interval between one estrus and another is, on average, seven months, however, this may range between 4 to 12 months. This interestrous period is not influenced by the photoperiod or pregnancy. The average duration of estrus is 9 days with spontaneous ovulation usually about 3 days after the onset of estrus.

For several days before estrus, a phase called proestrus, the bitch may show greater interest in male dogs and "flirt" with them (proceptive behavior). There is progressive vulval swelling and some bleeding. If males try to mount a bitch during proestrus, she may avoid mating by sitting down or turning round and growling or snapping.

Estrous behavior in the bitch is usually indicated by her standing still with the tail held up, or to the side of the perineum, when the male sniffs the vulva and attempts to mount. This tail position is sometimes called “flagging”. The bitch may also turn, presenting the vulva to the male.

The male dog mounts the female and is able to achieve intromission with a non-erect penis, which contains a bone called the os penis. The dog's penis enlarges inside the vagina, thereby preventing its withdrawal; this is sometimes known as the “tie” or “copulatory lock”. The male dog rapidly thrust into the female for 1–2 minutes then dismounts with the erect penis still inside the vagina, and turns to stand rear-end to rear-end with the bitch for up to 30 to 40 minutes; the penis is twisted 180 degrees in a lateral plane. During this time, prostatic fluid is ejaculated.

The bitch can bear another litter within 8 months of the previous one. Dogs are polygamous in contrast to wolves that are generally monogamous. Therefore, dogs have no pair bonding and the protection of a single mate, but rather have multiple mates in a year. The consequence is that wolves put a lot of energy into producing a few pups in contrast to dogs that maximize the production of pups. This higher pup production rate enables dogs to maintain or even increase their population with a lower pup survival rate than wolves, and allows dogs a greater capacity than wolves to grow their population after a population crash or when entering a new habitat. It is proposed that these differences are an alternative breeding strategy, one adapted to a life of scavenging instead of hunting.

Parenting and early life

All of the wild members of the genus Canis display complex coordinated parental behaviors. Wolf pups are cared primarily by their mother for the first 3 months of their life when she remains in the den with them while they rely on her milk for sustenance and her presence for protection. The father brings her food. Once they leave the den and can chew, the parents and pups from previous years regurgitate food for them. Wolf pups become independent by 5 to 8 months, although they often stay with their parents for years. In contrast, dog pups are cared for by the mother and rely on her for milk and protection but she gets no help from the father nor other dogs. Once pups are weaned around 10 weeks they are independent and receive no further maternal care.

Behavior problems

A survey of 203 dog owners in Melbourne, Australia, found that the main behaviour problems reported by owners were overexcitement (63%) and jumping up on people (56%).

Separation anxiety

When dogs are separated from humans, usually the owner, they often display behaviours such as destructiveness, faecal or urinary elimination, hypersalivation or vocalisation. Dogs from single-owner homes are approximately 2.5 times more likely to have separation anxiety compared to dogs from multiple-owner homes. Furthermore, sexually intact dogs are only one third as likely to have separation anxiety as neutered dogs. The sex of dogs and whether there is another pet in the home do not have an effect on separation anxiety.

Tail chasing

Tail chasing can be classified as a stereotypy. In one clinical study on the behaval problem, 18 tail-chasing terriers were given clomipramine orally at a dosage of 1 to 2 mg/kg (0.5 to 0.9 mg/lb) of body weight, every 12 hours. Three of the dogs required treatment at a slightly higher dosage range to control tail chasing, however, after 1 to 12 weeks of treatment, 9 of 12 dogs were reported to have a 75% or greater reduction in tail chasing.

Behavior compared to other canids

Comparisons made within the wolf-like canids allows the identification of those behaviors that may have been inherited from common ancestry and those that may have been the result of domestication or other relatively recent environmental changes. Studies of free-ranging African Basenjis and New Guinea Singing Dogs indicate that their behavioral and ecological traits were the result of environmental selection pressures or selective breeding choices and not the result of artificial selection imposed by humans.

Social structure

Among canids, packs are the social units that hunt, rear young and protect a communal territory as a stable group and their members are usually related. Members of the feral dog group are usually not related. Feral dog groups are composed of a stable 2-6 members compared to the 2-15 member wolf pack whose size fluctuates with the availability of prey and reaches a maximum in winter time. The feral dog group consists of monogamous breeding pairs compared to the one breeding pair of the wolf pack. Agonistic behavior does not extend to the individual level and does not support a higher social structure compared to the ritualized agonistic behavior of the wolf pack that upholds its social structure. Feral pups have a very high mortality rate that adds little to the group size, with studies showing that adults are usually killed through accidents with humans, therefore other dogs need to be co-opted from villages to maintain stable group size.

Socialization

The critical period for socialization begins with walking and exploring the environment. Dog and wolf pups both develop the ability to see, hear and smell at 4 weeks of age. Dogs begin to explore the world around them at 4 weeks of age with these senses available to them, while wolves begin to explore at 2 weeks of age when they have the sense of smell but are functionally blind and deaf. The consequences of this is that more things are novel and frightening to wolf pups. The critical period for socialization closes with the avoidance of novelty, when the animal runs away from - rather than approaching and exploring - novel objects. For dogs this develops between 4 and 8 weeks of age. Wolves reach the end of the critical period after 6 weeks, after which it is not possible to socialize a wolf.

Dog puppies require as little as 90 minutes of contact with humans during their critical period of socialization to form a social attachment. This will not create a highly social pet but a dog that will solicit human attention. Wolves require 24 hours contact a day starting before 3 weeks of age. To create a socialized wolf the pups are removed from the den at 10 days of age, kept in constant human contact until they are 4 weeks old when they begin to bite their sleeping human companions, then spend only their waking hours in the presence of humans. This socialization process continues until age 4 months, when the pups can join other captive wolves but will require daily human contact to remain socialized. Despite this intensive socialization process, a well-socialized wolf will behave differently to a well-socialized dog and will display species-typical hunting and reproductive behaviors, only closer to humans than a wild wolf. These wolves do not generalize their socialization to all humans in the same manner as a socialized dog and they remain more fearful of novelty compared to socialized dogs.

In 1982, a study to observe the differences between dogs and wolves raised in similar conditions took place. The dog puppies preferred larger amounts of sleep at the beginning of their lives, while the wolf puppies were much more active. The dog puppies also preferred the company of humans, rather than their canine foster mother, though the wolf puppies were the exact opposite, spending more time with their foster mother. The dogs also showed a greater interest in the food given to them and paid little attention to their surroundings, while the wolf puppies found their surroundings to be much more intriguing than their food or food bowl. The wolf puppies were observed taking part in antagonistic play at a younger age, while the dog puppies did not display dominant/submissive roles until they were much older. The wolf puppies were rarely seen as being aggressive to each other or towards the other canines. On the other hand, the dog puppies were much more aggressive to each other and other canines, often seen full-on attacking their foster mother or one another.

Cognition

Despite claims that dogs show more human-like social cognition than wolves, several recent studies have demonstrated that if wolves are properly socialized to humans and have the opportunity to interact with humans regularly, then they too can succeed on some human-guided cognitive tasks, in some cases out-performing dogs at an individual level. Similar to dogs, wolves can also follow more complex point types made with body parts other than the human arm and hand (e.g. elbow, knee, foot). Both dogs and wolves have the cognitive capacity for prosocial behavior toward humans; however it is not guaranteed. For canids to perform well on traditional human-guided tasks (e.g. following the human point) both relevant lifetime experiences with humans - including socialization to humans during the critical period for social development - and opportunities to associate human body parts with certain outcomes (such as food being provided by human hands, a human throwing or kicking a ball, etc.) are required.

After undergoing training to solve a simple manipulation task, dogs that are faced with an insoluble version of the same problem look at the human, while socialized wolves do not.

Reproduction

Dogs reach sexual maturity and can reproduce during their first year in contrast to a wolf at two years. The dog female can bear another litter within 8 months of the last one. The canid genus is influenced by the photoperiod and generally reproduces in the springtime. Domestic dogs are not reliant on seasonality for reproduction in contrast to the wolf, coyote, Australian dingo and African basenji that may have only one, seasonal, estrus each year. Feral dogs are influenced by the photoperiod with around half of the breeding females mating in the springtime, which is thought to indicate an ancestral reproductive trait not overcome by domestication, as can be inferred from wolves and Cape hunting dogs.

Domestic dogs are polygamous in contrast to wolves that are generally monogamous. Therefore, domestic dogs have no pair bonding and the protection of a single mate, but rather have multiple mates in a year. There is no paternal care in dogs as opposed to wolves where all pack members assist the mother with the pups. The consequence is that wolves put a lot of energy into producing a few pups in contrast to dogs that maximize the production of pups. This higher pup production rate enables dogs to maintain or even increase their population with a lower pup survival rate than wolves, and allows dogs a greater capacity than wolves to grow their population after a population crash or when entering a new habitat. It is proposed that these differences are an alternative breeding strategy adapted to a life of scavenging instead of hunting. In contrast to domestic dogs, feral dogs are monogamous. Domestic dogs tend to have a litter size of 10, wolves 3, and feral dogs 5-8. Feral pups have a very high mortality rate with only 5% surviving at the age of one year, and sometimes the pups are left unattended making them vulnerable to predators. Domestic dogs stand alone among all canids for a total lack of paternal care.

Dogs differ from wolves and most other large canid species as they generally do not regurgitate food for their young, nor the young of other dogs in the same territory. However, this difference was not observed in all domestic dogs. Regurgitating of food by the females for the young, as well as care for the young by the males, has been observed in domestic dogs, dingos and in feral or semi-feral dogs. In one study of a group of free-ranging dogs, for the first 2 weeks immediately after parturition the lactating females were observed to be more aggressive to protect the pups. The male parents were in contact with the litters as ‘guard’ dogs for the first 6–8 weeks of the litters’ life. In absence of the mothers, they were observed to prevent the approach of strangers by vocalizations or even by physical attacks. Moreover, one male fed the litter by regurgitation showing the existence of paternal care in some free-roaming dogs

Space

Space used by feral dogs is not dissimilar from most other canids in that they use defined traditional areas (home ranges) that tend to be defended against intruders, and have core areas where most of their activities are undertaken. Urban domestic dogs have a home range of 2-61 hectares in contrast to a feral dogs home range of 58 square kilometers. Wolf home ranges vary from 78 square kilometers where prey is deer to 2.5 square kilometers at higher latitudes where prey is moose and caribou. Wolves will defend their territory based on prey abundance and pack density, however feral dogs will defend their home ranges all year. Where wolf ranges and feral dog ranges overlap, the feral dogs will site their core areas closer to human settlement.

Predation

Despite claims in the popular press, studies could not find evidence of a single predation on cattle by feral dogs. However, domestic dogs were responsible for the death of 3 calves over one 5-year study. Other studies in Europe and North America indicate only limited success in the consumption of wild boar, deer and other ungulates, however it could not be determined if this was predation or scavenging on carcasses. Studies have observed feral dogs conducting brief, uncoordinated chases of small game with constant barking - a technique without success.

In 2004, a study reviewed 5 other studies of feral dogs published between 1975 and 1995 and concluded that their pack structure is very loose and rarely involves any cooperative behavior, either in raising young or in obtaining food. Feral dogs are primarily scavengers, with studies showing that unlike their wild cousins, they are poor ungulate hunters, having little impact on wildlife populations where they are sympatric. However, several garbage dumps located within the feral dog's home range are important for their survival.

Dogs in human society

Further information: Human-canine bond

Dogs likely were the first animals to be domesticated and as such have shared a common environment with humans for over ten thousand years. Only recently, however, has this species' behavior been subject to scientific scrutiny. Most of this work has been inspired by research in human cognitive psychology and suggests that in many ways dogs are more human-like than any other species, including nonhuman primates.

Studies using an operant framework have indicated that humans can influence the behavior of dogs through food, petting and voice. Food and 20–30 seconds of petting maintained operant responding in dogs. Some dogs will show a preference for petting once food is readily available, and dogs will remain in close proximity to a person providing petting and show no satiation to that stimulus. Petting alone was sufficient to maintain the operant response of military dogs to voice commands, and responses to basic obedience commands in all dogs increased when only vocal praise was provided for correct responses.

A study using dogs that were trained to remain motionless while unsedated and unrestrained in an MRI scanner exhibited caudate activation to a hand signal associated with reward. Further work found that the magnitude of the canine caudate response is similar to that of humans, while the between-subject variability in dogs may be less than humans. In a further study, 5 scents were presented (self, familiar human, strange human, familiar dog, strange dog). While the olfactory bulb/peduncle was activated to a similar degree by all the scents, the caudate was activated maximally to the familiar human. Importantly, the scent of the familiar human was not the handler, meaning that the caudate response differentiated the scent in the absence of the person being present. The caudate activation suggested that not only did the dogs discriminate that scent from the others, they had a positive association with it. Although these signals came from two different people, the humans lived in the same household as the dog and therefore represented the dog's primary social circle. And while dogs should be highly tuned to the smell of items that are not comparable, it seems that the “reward response” is reserved for their humans.

Research has shown that there are individual differences in the interactions between dogs and their human masters that have significant effects on dog behavior. In 1997, a study showed that the type of relationship between dog and master, characterized as either companionship or working relationship, significantly affected the dog's performance on a cognitive problem-solving task. They speculate that companion dogs have a more dependent relationship with their owners, and look to them to solve problems. In contrast, working dogs are more independent.

Dogs in the family

Further information: Companion dog

Dogs at work

Service dogs are those that are trained to help people with disabilities. Detection dogs are trained to using their sense of smell to detect substances such as explosives, illegal drugs, wildlife scat, or blood. In science, dogs have helped humans understand about the conditioned reflex. Attack dogs, dogs that have been trained to attack on command, are employed in security, police, and military roles.

Attacks

Main article: Dog attack

A dog's teeth can inflict serious injuries

The human-dog relationship is based on unconditional trust, however if this trust is lost it will be difficult to reinstate. As a last resort, humans will use a slap but a dog will use a bite. A dog's thick fur protects it from the bite of another dog but humans are furless and are not so protected.

In the UK between 2005 and 2013, there were 17 fatal dog attacks. In 2007-08 there were 4,611 hospital admissions due to dog attacks, which increased to 5,221 in 2008-09. It has been estimated that more than 200,000 people a year are bitten by dogs in England, with the annual cost to the National Health Service of treating injuries about £3 million. A report published in 2014 stated there were 6,743 hospital admissions specifically caused by dog bites, a 5.8% increase from the 6,372 admissions in the previous 12 months.

In the US between 1979 and 1996, there were more than 300 human dog bite-related fatalities. In the US in 2013, there were 31 dog-bite related deaths. Each year, more than 4.5 million people in the US are bitten by dogs and almost 1 in 5 require medical attention.

Attack training is condemned by some as promoting ferocity in dogs; a 1975 American study showed that 10% of dogs that have bitten a person received attack dog training at some point.

See also

• Gray wolf#Behavior
• Alpha roll
• Dog communication
• Dog intelligence
• Pack (canine)
• Pack hunter
• Separation anxiety disorder (humans)

Further reading

• Hare, Brian & Woods, Venessa. The Genius of Dogs (2013 Penguin Publishing Group) Reveals research findings about how dogs think and how we humans can have deeper relationships with them.
• Miklosi, Adam. Dog Behaviour, Evolution, and Cognition (2007 Oxford University Press) Provides a basis for a complete dog behavioural biology based on concepts derived from contemporary ethology.
• Pet Behavior articles from the ASPCA