Sex Differences in Dog Behavior and Cognition: What the Data Show

1. Why the Question Is Harder Than It Looks

1.1 What a "Sex Difference" Means

Few questions come up as often before a dog joins a household as this one: male or female? Behind it usually sit expectations. Males are said to be bolder, more independent and more likely to fight; females are said to be more attached, easier to train and more sensitive. Some of these expectations have a basis in data. Many do not, and almost none of them hold in the form in which they are usually expressed.

The first step is to be clear about what a sex difference in a study actually is. When researchers report that males scored higher than females on a trait, they mean that the average score of the male group was higher than the average score of the female group, and that this difference was unlikely to be produced by chance alone in a sample of that size. They do not mean that every male scored higher than every female, and they do not mean that the difference is large. In large samples, very small average differences become statistically significant. A study of thousands of dogs can detect a difference so small that, if you placed a randomly chosen male and a randomly chosen female side by side, the female would still score higher than the male in a large share of comparisons.

This is the central point of this article. The distributions of male and female dogs on almost every behavioral trait that has been studied overlap heavily. Knowing the sex of a dog tells you something about the average of a group the dog belongs to. It tells you very little about the dog in front of you.

1.2 Two Kinds of Difference

It helps to separate two kinds of behavioral difference between the sexes. The first kind consists of behaviors that are tied closely to reproduction and that differ in form, not only in frequency. Urine marking with a raised leg is the clearest example in dogs. Mounting and roaming in intact males belong in the same group. These behaviors are sexually dimorphic in the biological sense: their typical form differs between males and females, and they are sensitive to gonadal hormones.

The second kind concerns personality traits, emotional tendencies and cognitive performance: boldness, sociability, fearfulness, aggression, attention to social cues, problem solving and the like. Here the question is not whether the behavior exists in one sex and not in the other, but whether its average level differs. This is where most of the popular claims are located, and this is where the data are weakest and most confounded.

Mixing the two kinds is a common error. The fact that intact males mark more and in a different posture says nothing about whether males are more loyal, less trainable or harder to live with. The robustness of the first kind of difference does not transfer to the second.

1.3 Where the Data Come From

The evidence on sex differences in dogs comes from three main sources. Large owner questionnaires, often based on the Canine Behavioral Assessment and Research Questionnaire, a validated instrument developed for pet dogs (Hsu & Serpell, 2003), provide sample sizes in the thousands or tens of thousands. Standardized behavior tests, mainly from working-dog and service-dog programs, provide trained evaluators and consistent procedures, but usually concern only a few breeds. Experimental studies in cognition provide controlled procedures and direct observation, but usually involve a few dozen dogs.

Each source has a characteristic weakness: questionnaires depend on what owners notice and believe, test data on the population tested, and experiments on small samples and on the interpretation of measures such as looking time. A sex difference that appears in only one type of source deserves more caution than one that appears across several. How such measures are defined and what they can capture is a question of its own (how dog behavior is turned into measurable data).

2. The Confounds: Why Sex Rarely Acts Alone

2.1 Neuter Status

In most pet dog populations, sex cannot be separated cleanly from neuter status. Many dogs in the large questionnaire studies are neutered, the proportion differs between males and females, and the reasons and timing of neutering differ too. A comparison of "males" and "females" is therefore usually a comparison of mixed groups of intact and neutered males with mixed groups of intact and neutered females.

The neuter data themselves show that this matters, and that it matters differently for the two sexes. In a C-BARQ analysis of 6,235 male dogs, longer lifetime exposure to gonadal hormones was associated with reduced reporting of 26 mostly unwelcome behaviors, eight of them related to fearfulness and seven to aggression. Only indoor urine marking and howling when left alone were more likely with longer exposure (McGreevy et al., 2018). The same approach applied to 8,981 females found that ten unwelcome behaviors were reported less often with longer hormone exposure, of which one related to fearfulness and three to aggression (Starling et al., 2019). In other words, the relationship between hormones and behavior is not the same in males and females, and a sex comparison that ignores neuter status mixes several different relationships.

This article does not discuss neutering decisions. The point here is narrower: neuter status is a confounder of sex comparisons, and any reported sex difference in a population with many neutered dogs may partly reflect differences in neutering rather than differences between the sexes as such. The evidence on neutering itself is reviewed separately (what neutering does and does not change in behavior).

2.2 Size and Breed

In most breeds, males are larger and heavier than females. Size is associated with behavior in its own right, through how people handle and react to a dog, how other dogs respond to it, and possibly through physiology. Any sex comparison that does not account for size may partly be a size comparison.

Breed is a second, larger confound. Breeds differ in many traits, and breeds also differ in their composition. In a C-BARQ study of breed differences in aggression, breeds differed in their ratio of intact to neutered dogs in both samples examined, and in the online sample they also differed in sex ratio (Duffy, Hsu & Serpell, 2008). If one breed contributes more males and is also bolder on average, a pooled analysis can produce a sex difference that is partly a breed difference. In an Australian owner survey, boldness differed among breeds and breed groups (Starling, Branson, Thomson & McGreevy, 2013b), which illustrates how strongly breed composition can shape the trait itself. The relationship between breed and behavior is examined in more detail elsewhere (what breed does and does not predict).

The same breed study adds a further point that applies equally to sex. Because of the substantial variation within breeds, the authors concluded that "it is inappropriate to make predictions about a given dog's propensity for aggressive behavior based solely on its breed" (Duffy et al., 2008). The logic is identical for sex: a group average does not predict the individual when variation within the group is large.

2.3 How Owners Keep and Treat Their Dogs

Male and female dogs are not necessarily kept in the same way. They may be acquired at different ages, used for different purposes, trained differently and exercised differently. Owners may choose a sex because of expectations and then treat the dog in line with those expectations.

Management factors are clearly associated with personality. In a survey of 1,978 Labrador Retrievers, the working status of the dog was more commonly associated with differences in personality than the other factors analyzed, and dogs that were exercised for longer showed less aggression, less fear of people and objects and lower separation anxiety (Lofgren et al., 2014). In a very large German-language online sample, calmness was associated with age, neuter status, the number of types of professional training and the age at which the dog was acquired, and boldness was associated with the age at acquisition as well as with sex (Kubinyi, Turcsán & Miklósi, 2009).

Owner characteristics can matter too. In a C-BARQ regression analysis, higher owner-directed aggression scores were associated with male dogs, older dogs, being neutered or spayed, having female owners, fewer other dogs in the household and being kept outside the house (Hsu & Sun, 2010). The list itself shows the problem: sex of the dog appears alongside sex of the owner, neuter status and housing. These variables are correlated with one another in real households, and a cross-sectional analysis cannot fully separate them.

2.4 Reporting Bias and Expectations

Most large data sets on dog personality are owner reports. Owners report what they notice, and what they notice depends partly on what they expect. If owners believe that males are bolder, they may interpret ambiguous behavior in males as boldness and the same behavior in females as something else. In owner surveys of breed differences, such as the Australian boldness study (Starling et al., 2013b), actual behavior cannot be fully separated from expectations based on breed stereotypes, and the same limitation applies to sex stereotypes.

Validated instruments reduce some sources of error but cannot remove expectation effects completely. The breed aggression study noted that questionnaire reports "inevitably involve a degree of subjectivity" (Duffy et al., 2008). For sex differences, this means that small average differences in owner reports should not be read as direct measures of behavior.

3. Sexually Dimorphic Behavior: Elimination and Marking

3.1 The Raised-Leg Posture

The most visible behavioral difference between male and female dogs is the posture used during urination. Adult males typically urinate with one hind leg raised, and urination in males functions to a large extent as scent marking. A study of shelter dogs summarized previous findings that the raised-leg posture is used in a very high proportion of urinations by mature males: 94 to 97 percent under conditions outside the shelter, compared with 73 percent of urinations by adult males in their own shelter sample (McGuire, Fry, Orantes, Underkofler & Parry, 2020). The same authors noted that adult males that normally used the raised-leg posture "temporarily reverted in fearful situations to using the juvenile lean-forward posture" in which all four feet stay on the ground.

Even the clearest sex difference in dog behavior is not fixed. Its expression depends on context and on the dog's emotional state. A male that squats in an unfamiliar or stressful place is not behaving abnormally for a male; he is behaving in a way that has been described in stressed males.

3.2 Females Mark, Too

The common idea that only males mark is not supported. In a study of female Jack Russell Terriers, females used several urination postures, including the squat, a squat with one leg raised, an arched posture with one leg raised and even a handstand, with the squat-raise being the most common. Raised postures were used more often when the dogs were away from their home area than when they were on it (Wirant & McGuire, 2004). This pattern fits scent marking: depositing urine at a height and in places where it will be detected by other dogs.

The difference between the sexes in marking is therefore a difference in frequency, posture and context sensitivity, not a strict yes-or-no difference. Smell is the channel through which this information is exchanged, and how dogs process odors is discussed elsewhere (how olfaction shapes dog behavior).

3.3 Context Shapes Marking

Marking also responds to social context, and here the sexes differed in an unexpected way. In 100 shelter dogs aged at least one year (57 males and 43 females), males urinated at higher rates when walked by unfamiliar women than when walked by unfamiliar men, whereas females urinated at similar rates with both (McGuire et al., 2020). The study does not explain why, and the shelter setting limits transfer, but it shows that a sexually dimorphic behavior can be modulated by social factors that have nothing to do with other dogs.

3.4 Hormones and Marking

Marking in males is sensitive to gonadal hormones. In 57 adult male dogs castrated for problem behaviors, urine marking, mounting and roaming improved by at least 50 percent in at least 60 percent of dogs, whereas for aggression an improvement of that size was seen in fewer than a third (Neilson, Eckstein & Hart, 1997). In the large C-BARQ data set on males, indoor urine marking was one of only two behaviors that were more likely with longer hormone exposure (McGreevy et al., 2018).

These results support the distinction made in section 1.2. Behaviors linked to reproduction respond to hormones in a relatively consistent way. Emotional and personality traits do not, or not in the same direction. The broader picture of how testosterone relates to behavior, and where popular claims go beyond the data, is covered in detail elsewhere (what testosterone does and does not explain).

In practice: Marking in the house or on walks is one of the few areas where the sex of the dog is genuinely informative, but it is not decisive. In training practice, we regularly meet females that mark intensively and males that hardly mark at all. Marking that appears suddenly or increases is a reason to look at the situation, including stress and medical causes, not at the dog's sex.

4. Personality and Temperament

4.1 Boldness

Boldness is the trait for which a sex difference has been reported most consistently. In an Australian owner survey, boldness decreased with age, males were bolder than females, and intact dogs were bolder than neutered dogs (Starling, Branson, Thomson & McGreevy, 2013a). The statistical tests were significant for all three factors, but the published summary does not translate them into an effect size that would show how large the sex difference is.

The large German-language online study of 14,004 dogs found the same direction. Boldness was associated with sex, age and age at acquisition. The boldest dogs were males acquired before the age of 12 weeks and younger than two years; the least bold were females acquired after the age of one year or bred by the owner (Kubinyi et al., 2009). This result is often quoted as "males are bolder", but the regression trees show something more interesting: sex appears together with age at acquisition and with the dog's age, and the combination matters more than sex alone. A female acquired early is not represented by the "least bold" group, and a male acquired late is not represented by the "boldest" group.

A review of sex differences in dogs concluded that boldness and aggressiveness, described as a behavioral syndrome, were reported as higher in males than in females in several studies (Scandurra, Alterisio, Di Cosmo & D'Aniello, 2018). The same review was cautious about how robust these conclusions are, as discussed in section 5.4. Boldness itself, and how it relates to coping styles and temperament, is discussed in more detail elsewhere (how temperament and personality are studied in dogs).

4.2 Sociability Toward Other Dogs

In the same online sample, males were less sociable toward other dogs than females. Sociability toward conspecifics was mainly associated with age, sex, training experience and the time owners spent with their dogs, and the least sociable dogs were older than 4.8 years and spent less than three hours a day with their owners (Kubinyi et al., 2009). Once again, sex is one factor among several, and age and lifestyle appear at least as prominently.

The authors themselves pointed out that the characteristics were reported by owners and that the associations "do not necessarily represent a causal relationship" (Kubinyi et al., 2009). That caution is worth keeping. An owner who expects males to be less tolerant of other dogs may keep a male away from other dogs more often, which would in turn affect his social experience.

4.3 Standardized Tests in Working Dogs

Data from standardized testing programs are less dependent on owner perception. In a Swedish service-dog program, test results of 1,310 German Shepherds and 797 Labrador Retrievers aged 450 to 600 days showed marked differences between breeds and between the sexes (Wilsson & Sundgren, 1997). In both breeds, males scored higher than females on traits labeled courage, prey drive and defence drive. For the trait labeled cooperation, the direction differed between breeds: it was higher in males among German Shepherds and higher in females among Labradors.

Three points limit the transfer of these results. First, the dogs were young adults from a selective breeding program, not a cross-section of pet dogs. Second, the traits were scored by evaluators on a test designed for selecting service dogs, so the labels describe test behavior, not everyday behavior. Third, the reversal of the sex difference for cooperation between the two breeds shows that a sex difference in one breed cannot simply be assumed in another. How well such tests predict later behavior is a separate question (what behavior tests can and cannot predict).

4.4 Anxiety-Related Traits

The largest data set on anxiety-related traits comes from a Finnish questionnaire study of about 13,700 pet dogs (Salonen et al., 2020). Male dogs were more often reported as aggressive, inattentive and hyperactive or impulsive, and separation-related behavior was slightly more common in males. Female dogs were more often reported as fearful. Noise sensitivity, fear of surfaces and compulsive behavior occurred independently of sex.

This pattern is informative for two reasons. First, it is mixed: neither sex is generally more "problematic", and the differences run in both directions depending on the trait. Second, the most common anxiety-related trait in many populations, noise sensitivity, showed no sex difference at all in this sample. Breed differences in the same study were much more prominent than sex differences and were the focus of the paper. The neurobiology of fear and anxiety is discussed elsewhere (how anxiety works in the dog's brain).

For fearfulness in females, the neuter data are relevant again. In females, longer hormone exposure was associated with fewer reports of only one fear-related behavior (Starling et al., 2019), whereas in males it was associated with fewer reports of eight (McGreevy et al., 2018). Whether the higher fearfulness reported for females in pooled samples reflects sex, neutering patterns, or both, cannot be answered from the available cross-sectional data.

5. Aggression

5.1 What the Large Surveys Show

Aggression is the trait that most strongly shapes popular ideas about male and female dogs. The data are more mixed than the ideas. In the Finnish sample, males were more often reported as aggressive (Salonen et al., 2020). In a C-BARQ regression analysis, higher scores on owner-directed aggression were associated with male dogs, but also with older dogs, neutered or spayed dogs, female owners, fewer other dogs in the household and keeping the dog outside (Hsu & Sun, 2010).

A large UK survey of owner-reported human-directed aggression, based on roughly four thousand returned questionnaires, found that aggression toward unfamiliar people entering the house was reported in about seven percent of dogs and toward family members in about three percent (Casey, Loftus, Bolster, Richards & Blackwell, 2014). Neutered females had a reduced risk of aggression in all three contexts examined. At the same time, the variables measured explained a relatively small amount of the variance, less than ten percent, between aggressive and non-aggressive dogs (Casey et al., 2014).

That last figure deserves emphasis. Even when sex, neuter status and other demographic factors are associated with aggression in a statistically significant way, together they explain only a small part of the difference between dogs that show aggression and dogs that do not. Most of the variation lies elsewhere: in experience, context, learning history, health and the individual dog.

5.2 Context Matters More Than Category

The same UK survey found that aggression in different contexts did not broadly co-occur: a dog aggressive toward visitors was often not aggressive toward family members, and the reverse (Casey et al., 2014). This finding cuts against the idea of an "aggressive sex". If aggression is largely tied to specific situations, then a sex difference in an overall aggression score says little about which situations a particular male or female dog will find difficult. The broader research on aggression is reviewed elsewhere (what the research on aggression in dogs shows).

5.3 Neuter Status and Aggression

Aggression is also where the neuter confound is most entangled with sex. In the largest C-BARQ analysis of gonadectomy and aggression, with dogs neutered because of behavior problems excluded, neutering showed no association with aggression toward familiar people or other dogs and only a small increase toward strangers in one of two models (Farhoody et al., 2018). In males, longer hormone exposure was associated with fewer reports of seven aggression-related behaviors (McGreevy et al., 2018), and in females with fewer reports of three (Starling et al., 2019).

Taken together, these data do not support the simple idea that males are more aggressive because of testosterone and that removing testosterone removes aggression. The relationship between hormones, sex and aggression is more complex, and the hormone side of it is discussed elsewhere (how hormones and neurochemistry shape behavior).

5.4 What the Review Concluded

The review of sex differences in dogs is notably careful on aggression. It noted that several studies reported higher aggressiveness in males, but pointed to small and non-representative samples, owner surveys of limited reliability and the limited range of contexts tested. Its conclusion was that "the conclusion that male dogs are more aggressive would seem not robust" (Scandurra et al., 2018). The review also pointed to the neuter confound in the opposite direction: because ovariectomy has been associated with increased aggressive behavior in females in some studies, neutered females may have biased the results of studies that compared the sexes.

In practice: In behavior consultations, the sex of a dog with an aggression problem is rarely the most useful piece of information. What helps is a precise description of the situations, the warning signals that precede the behavior, the dog's health and what the behavior achieves for the dog. This is an observation from our work, not a study finding, but it fits the survey data showing that demographic variables explain little of the variation.

6. Play and Social Behavior

6.1 Play Between Littermates

One of the few longitudinal observational studies relevant to sex differences followed play in four litters of puppies from 3 to 40 weeks of age (Ward, Bauer & Smuts, 2008). In mixed-sex pairs, males initiated play more often than females, showed more offensive play behavior toward females, and also self-handicapped more, that is, they more often adopted the weaker role or restrained themselves in play. In same-sex pairs, females initiated play with females across all periods, whereas males initiated play with males more only in the latest period. Play bows did not differ between the sexes.

Males were both more offensive and more self-handicapping toward females, which suggests that the asymmetry is about how play is structured between the sexes rather than about one sex being "rougher" overall. The study is small, involved four litters only and observed puppies under particular household conditions, so the results describe patterns in these litters rather than general rules. How play develops and what it does for the dog is discussed elsewhere (how play develops and what it does).

6.2 Human-Directed Social Behavior

A large standardized study tested 498 laboratory-bred beagles in an unsolvable problem task, in which dogs that cannot obtain a reward on their own often turn to a human. Females scored significantly higher on social interaction with the human and on physical contact, and heritability estimates for the two largest behavioral components ranged from 0.23 to 0.32. Eye-contact seeking increased with age and experience (Persson, Roth, Johnsson, Wright & Jensen, 2015).

This study has strengths that most sex comparisons lack: a large sample, one breed, standardized rearing and housing, and a standardized test. It also has a clear limit: laboratory beagles kept under identical conditions are not family dogs, and the unsolvable task measures one specific situation. The review summarized this and similar findings as a tendency of females to be more socially oriented toward humans in cooperative or problem-solving contexts, while males in some data showed more inclination to social play with humans (Scandurra et al., 2018). The direction of the difference therefore depends on what kind of social behavior is measured.

7. Cognition and Perception

7.1 A Size Constancy Experiment

The cognitive study most often quoted on sex differences in dogs used a violation-of-expectation design. Fifty dogs, 25 males and 25 females aged one to ten years, watched a ball roll behind a screen and reappear either at the same size or at a different size. Female dogs looked significantly longer at the reappearing ball when its size had changed than when it had stayed the same; male dogs showed no such difference. The interaction between sex and condition was significant, and neuter status did not affect the results (Müller, Mayer, Dörrenberg, Huber & Range, 2011).

The finding is often summarized as "female dogs are smarter". That summary is not supported. The study tested one specific expectation, with a single trial per dog, using looking time as the measure. Looking time indicates that something attracted attention; whether it reflects an expectation in the cognitive sense is an interpretation, and males that did not look longer may have noticed the change without lingering on it. The authors' own result is narrower and more precise: in this setup, females responded to a size violation and males did not.

The review placed this result in a broader pattern: females were described as focusing more on single social and physical stimuli and as relying more on visual cues, whereas males in some spatial tasks were described as more flexible in switching navigation strategies (Scandurra et al., 2018). These are interpretive syntheses across few and small studies, and the review itself noted that data on problem solving were limited. The wider research on what dogs can do cognitively is discussed elsewhere (what is known about cognitive abilities in dogs).

7.2 Gestures and Words

A study of water rescue dogs trained to respond to both gestural and verbal commands presented the dogs with incongruent information, a gesture pointing one way and a verbal command meaning another. Overall, dogs tended to follow the gesture. Females were more responsive to gestures, while males performed better with verbal commands (D'Aniello, Scandurra, Alterisio, Valsecchi & Prato-Previde, 2016). The dogs were a specialized working population, and the result describes behavior in a particular training system. How dogs read human gestures more generally is discussed elsewhere (how dogs understand human gestures).

Taken together with the size constancy study and the beagle data, a pattern appears that is consistent with greater attention to visual and social cues in females in some tasks. A much larger study of 1,032 pet dogs adds an important data point: females were more successful in the cylinder test, a measure of inhibitory control, and showed more human-directed behavior in an unsolvable task, while males spent more time working independently. Neuter status did not explain these differences in the subset for which reproductive status was known (Junttila, Huohvanainen & Tiira, 2021). Even these findings do not mean that females are generally "smarter" or more cooperative: the study measured two specific tasks, and group differences cannot reliably predict an individual dog.

8. Laterality: Paw Preference and Sex

8.1 Opposite Directions in a Small Sample

Lateralized behavior, such as a preferred paw, has been examined for sex differences more often than most other traits. In 80 intact mixed-breed and purebred dogs, a task requiring the dog to remove a piece of adhesive paper from its snout showed population-level lateralization in opposite directions: males preferentially used the left paw and females the right paw (Quaranta, Siniscalchi, Frate & Vallortigara, 2004). Earlier work on lateralized behavior in dogs is listed by later reviews among the studies reporting a sex-related difference in paw use (Wells, 2003).

8.2 A Very Large Sample

A much larger data set on 17,901 dogs gave a more nuanced picture. Among dogs that showed a paw preference, there was a population-level right-paw preference in both sexes, with 60.7 percent of females and 56.1 percent of males right-pawed, and the proportion of right-pawed dogs was significantly higher in females (Laverack, Pike, Cooper & Frasnelli, 2021). Older dogs tended to show a stronger right-paw bias than younger dogs.

Compared with the small study, the direction of the sex difference is the same (females more right-pawed), but the size is modest and males are not on average left-pawed. The difference in right-pawedness between the sexes amounts to less than five percentage points.

8.3 Age Complicates the Picture

A study on owner handedness and paw preference found that females showed a right-paw bias more than males and that older males showed a right-paw bias more than younger males (Charlton & Frasnelli, 2022). The authors summarized the earlier literature as showing a higher percentage of right-pawedness in females than in males. If the age pattern in males is confirmed, part of the sex difference reported in samples with many young dogs may be an age-by-sex interaction rather than a stable difference.

8.4 Inconsistency Across Tasks

The review noted that most studies supported a male left, female right pattern, but that results with a food toy task were contradictory and that at least one study failed to replicate consistent sex differences (Scandurra et al., 2018). Paw preference depends on the task, and different tasks do not always produce the same classification for the same dog. The broader topic of lateralization in dogs, including sensory asymmetries, is discussed elsewhere (what laterality research shows about the dog's brain).

9. Biology, Development and Selection

9.1 Where Sex Differences Might Come From

The review concluded that sex differences in dogs are largely in line with life-history theory and appear to be rooted mainly in the species' biological and evolutionary heritage, remaining in place despite artificial selection. At the same time, one pattern known from wild canids, a higher intraspecific sociability of males, was not replicated in dogs (Scandurra et al., 2018). In the large online sample, males were in fact less sociable toward other dogs than females (Kubinyi et al., 2009).

Biological explanations are plausible for the reproductive behaviors described in section 3. For personality and cognitive traits, they are hypotheses. Hormone exposure, size, growth rate and age at maturation all differ between the sexes, and none of the studies reviewed here was designed to separate them.

9.2 Genetic Variation Within the Sexes

The beagle study is a reminder that much of the variation in social behavior lies within each sex. Heritability estimates of 0.23 to 0.32 for human-directed social behavior were obtained in a population in which females also scored higher on average (Persson et al., 2015). The two findings are compatible: a trait can show both a modest average sex difference and substantial genetic variation between individuals of the same sex. For the individual dog, the latter is usually more informative. The broader research on genes and behavior is reviewed elsewhere (what behavioral genetics shows about dogs).

10. Male or Female? Choosing Without Stereotypes

10.1 What the Data Allow

If the data are taken seriously, they support a few cautious statements. Intact males mark more, with a raised-leg posture, and this behavior is sensitive to hormones and context. In several large owner samples, males were reported on average as somewhat bolder and less sociable toward other dogs, and females as somewhat more fearful. In a few experimental studies, females were more oriented toward visual and social cues. In aggression, the data are mixed and strongly confounded, and the variables measured explain little of the variation.

What the data do not allow is a prediction for an individual dog. None of the studies reviewed here reports effect sizes that would make the sex of a dog a strong predictor of its personality. Breed, age, early experience, management and the individual all appear at least as prominently, and often more prominently, in the same analyses.

10.2 Better Questions to Ask

For someone choosing a dog, the more useful questions concern the individual and the situation. How does this dog respond to strangers, to other dogs and to new environments? What is known about its parents and its early experience? How old is it, and how will age change things over the coming years?

In practice: When families ask whether they should choose a male or a female, we usually turn the question around: what kind of everyday life will the dog have, and which individual dog fits it? In our experience from training practice, this question leads to better decisions than any rule about sex. A calm, socially easy male and a bold, independent female are both common.

10.3 Multi-Dog Households

Many owners have heard that mixed-sex pairs get along better than same-sex pairs. The studies reviewed here do not test this directly. The littermate study shows that play between males and females was structured differently than play within each sex (Ward et al., 2008), but it does not show which combinations of adult dogs live together more peacefully.

In practice: Whether two dogs get along depends in our experience far more on their individual temperaments, ages, social skills and the management of resources and space than on their sex. We see harmonious same-sex pairs and conflict-ridden mixed pairs regularly. This is a practical observation, not a research finding, and a well-designed study of this question in family dogs is still missing.

11. Summary at a Glance

The clearest sex differences in dogs concern reproductive behaviors such as urine marking. Adult males use the raised-leg posture in most urinations under ordinary conditions, revert to a lower posture in fearful situations, and mark at different rates depending on social context (McGuire et al., 2020). Females also mark and use raised postures, especially away from home (Wirant & McGuire, 2004). Castration reduces marking in many but not all males (Neilson et al., 1997).

For personality traits, large owner samples reported males as bolder on average (Starling et al., 2013a; Kubinyi et al., 2009) and less sociable toward other dogs (Kubinyi et al., 2009). A Finnish sample found more aggression, inattention and hyperactivity reported in males and more fearfulness in females, with no sex difference in noise sensitivity (Salonen et al., 2020). Standardized test data from two working breeds showed sex differences whose direction depended on the trait and, for cooperation, on the breed (Wilsson & Sundgren, 1997).

For aggression, associations with sex are mixed and entangled with neuter status, owner characteristics and housing (Hsu & Sun, 2010; Casey et al., 2014), and demographic variables explained less than ten percent of the variance in one large survey (Casey et al., 2014). A review considered the conclusion that males are more aggressive not robust (Scandurra et al., 2018).

In cognition and social behavior, females showed a response to a size constancy violation that males did not (Müller et al., 2011), more human-directed social behavior in an unsolvable task (Persson et al., 2015) and greater responsiveness to gestures in one working population (D'Aniello et al., 2016). In laterality, females were more often right-pawed, but the difference in a very large sample was modest (Laverack et al., 2021; Quaranta et al., 2004; Charlton & Frasnelli, 2022).

12. Research Gaps and Critical Appraisal

12.1 Effect Sizes Are Missing

Most studies report whether a sex difference is statistically significant, not how large it is. In samples of several thousand dogs, very small differences become significant. Without standardized effect sizes or measures of overlap, readers cannot judge whether a reported difference matters for real dogs. The one area with directly interpretable percentages, paw preference, shows a difference of under five percentage points in the largest sample (Laverack et al., 2021).

12.2 Questionnaires Dominate

The largest data sets are owner reports (Kubinyi et al., 2009; Salonen et al., 2020; Starling et al., 2013a; Casey et al., 2014). They allow large samples, but they measure what owners notice and believe. Expectation effects related to sex cannot be ruled out, and none of the studies reviewed here tested whether owners rate identical behavior differently in males and females.

12.3 Confounds Are Rarely Separated

Sex, neuter status, age at neutering, size, breed and management are correlated in real populations. Few studies model them jointly, and none of the cross-sectional studies can establish causality. The neuter data show that hormone exposure relates to behavior differently in males and females (McGreevy et al., 2018; Starling et al., 2019), which means that a sex effect estimated in a mixed population depends on the neutering practices of that population.

12.4 Experimental Samples Are Small and Specific

The cognitive studies involve small samples (50 dogs in the size constancy study) or specialized populations: laboratory beagles (Persson et al., 2015), water rescue dogs (D'Aniello et al., 2016) and service-dog candidates (Wilsson & Sundgren, 1997). Single-trial designs (Müller et al., 2011) are vulnerable to chance findings. Replications in independent samples of family dogs are largely missing.

12.5 Shelter and Laboratory Populations

The marking data in section 3.3 come from shelter dogs (McGuire et al., 2020), and the authors themselves documented that the shelter setting changed posture use. The beagle data come from a laboratory colony. Transfer to family dogs, which live in different social and physical environments, cannot be assumed.

12.6 Inconsistent Measures

Different studies measure "boldness", "sociability" or "aggression" with different instruments and different item sets. Paw preference depends on the task used. Results that appear to agree may be measuring different things, and results that appear to conflict may reflect differences in method rather than in dogs.

13. Conclusion

Male and female dogs differ, but less, and less simply, than everyday wisdom suggests. The robust differences are those tied to reproduction, such as urine marking with a raised leg, and even these depend on hormones, context and emotional state. For personality, aggression and cognition, the reported differences are mostly small, run in different directions for different traits, and are entangled with neuter status, size, breed, management and the expectations of the people who report them.

For the individual dog, sex is one weak piece of information among many. The data repeatedly show larger variation within each sex than between the sexes, and larger contributions from age, breed, experience and environment than from sex. Choosing a dog on the basis of its sex means choosing on the basis of a group average. Choosing on the basis of the individual dog, its history and the life it will lead is what the evidence supports.

Key Insights (Takeaways)

• Average sex differences in dog behavior are mostly small and the distributions overlap heavily; the sex of a dog predicts little about the individual.

• The clearest difference is urine marking: adult males usually lift a leg, but posture changes with fear and context, and females mark too (McGuire et al., 2020; Wirant & McGuire, 2004).

• Large owner surveys reported males as bolder and less sociable toward other dogs, and females as more fearful (Kubinyi et al., 2009; Salonen et al., 2020).

• Demographic variables, sex included, explained less than ten percent of the variance in human-directed aggression in one large survey (Casey et al., 2014).

• Sex is confounded with neuter status, size, breed, management and owner expectations, and hormones relate differently to behavior in males and females (McGreevy et al., 2018; Starling et al., 2019).

• Cognitive differences rest on few, small or specialized samples (Müller et al., 2011; Persson et al., 2015).

• Choosing a dog by its individual behavior, history and future life is better supported than choosing by sex.

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