Implicit measure.

Participants were presented with a modified ‘nature vs nurture’ task used to assess lay beliefs about heredity [22]. Participants were told that they were participating in a study to test their understanding of heredity in dogs. They were then randomly assigned to evaluate one of the four dog breeds, accompanied by the statement, “This is [name] he/she is a 4 year old [breed]”. The name and gender of the individual dogs were the same for each breed. Next, they were presented with a list of 10 traits and asked to rate the extent to which they thought each trait was the result of either genetic or environmental factors using a 7 point Likert scale (0 = all genetics; 6 = all environment). Definitions of both genetics and environment were anchored at scale extremes (genetics: a trait the individual is born with–inherited from mother and/or father; environment: a trait the individual is not born with–result of being raised by owner or breeder). The traits participants rated were presented in random order and included: fur color, aggression towards other dogs, playfulness, fear of people, dominance, excessive barking, body size, number of teeth, and the two traits of interest- tail length, ear shape and size.

Explicit measure.

After completing the nature-nurture task, participants were randomly assigned to receive two different images of the same breed of dog–one pictured in its natural state (long tail and ears) and one modified (cropped ears and docked tail). Participants were told “both of the above dogs are purebred [breed]. In fact, these two dogs are siblings, yet their ears and tails look very different” and then asked to select which one of the following three statements best explains this difference in physical appearance. Participants could select from the following three options:

1. Option A: Individual dogs of the same breed vary in appearance, meaning some will have tails and ears of different shapes and sizes.
2. Option B: Some dog breeds have part of their ears and tails surgically removed after they are born.
3. Option C: None of the above.
4. Options A and B were counterbalanced to minimize order effects. Option C always appeared last.

Finally, participants were asked to provide basic demographic information including age, gender, income and state of residence, if they were the primary caregiver of a dog and if they, or anyone they know, owned any of the dog breeds used as stimuli (Doberman Pinscher, Miniature Schnauzer, Boxer, Brussels Griffon).

Implicit measure.

Average scores (Mean±SD) were calculated for both tail length and ear conformation. The average scores for all breeds were 1.87±1.53 and 2.39±2.02 for ear conformation and tail length, respectively, with slight variation within each individual breed (see Table 2). No other stimuli (e.g. familiarity with dog breeds, age and gender) were significant.

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Table 2. Average (Mean±SD) responses obtained from participants (n = 810) when asked whether behavioural/physical dog traits were a result of genetics or the environment.

Participants were asked to rate based on a 7 point Likert scale (0 = all genetics; 6 = all environment).

https://doi.org/10.1371/journal.pone.0158131.t002

Explicit measure.

A majority 58% (n = 469) of participants answered correctly (i.e. “some dog breeds have part of their ears and tails surgically removed after they are born”) (see Table 3). Familiarity with dog breeds used as stimuli did not alter the results (P>0.05). Participants that self-reported as being a caretaker of a dog were more likely to answer the question correctly than those that were not dog owners, 68% vs 51% respectively. Of female participants 66% answered correctly, compared to 53% of male participants.

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Table 3. The number (and percentage) of participants that responded when presented with two dogs of the same breed with ear and tail conformation variation and asked the reason for this.

Multiple choice options included a) genetic variation, b) surgical removal after birth or c) none of the above.

https://doi.org/10.1371/journal.pone.0158131.t003

Experiment 1.

Our finding from Experiment 1 suggests that many people are simply unaware that the characteristic look of certain dogs is the result of surgical procedures. When participants were explicitly asked what explained different ear shape and tail length among dogs of the same breed slightly more, although a significant minority (42%) believed that tail length and ear conformation were a consequence of genetic variation. These results suggest that assessing public attitudes on contentious practices such as ear cropping and tail docking might be difficult given that a large minority of the individuals appear to be unaware that this practice takes place. The problem of non-attitudes, defined as a lack of strong or meaningful opinions on a matter, has been shown to result in attitude instability [32], which in turn can affect survey results [33]. This may also result in studies failing to truly reflect the publics’ attitude on a particular subject. Awareness studies can improve the ability to assess public attitudes as it attempts to account and arguably remove participants’ non-attitudes, resulting in more accurate results.

In the current study we observed that women appeared to be more explicitly aware that tail docking and ear cropping were not a result of genetic variation. This may be explained in part by women generally tending to be more involved in animal activism compared to men [34], which could subsequently mean women are more informed about these procedures. Not surprisingly, participants that were also primary caregivers of dogs were also more aware of these procedures compared to non-caregivers. Participants having no experience with dogs may be less aware (and arguably less interested in dogs per se) compared to those participants that did have experience with dogs. Additionally, given the natural variation in the length and type of tail across breeds, those participants with little experience with dogs may have considered the lack of the tail as being within the scope of the natural variation observed (e.g. some breeds such as the Australian Shepherd have naturally short tails).

Experiment 2.

Experiment 2 showed that modified dogs are perceived as being more aggressive, more dominant, less playful and less attractive than dogs in their natural state. This is in line with other research that shows differences in coat color and ear conformation can change personality attributes given to dogs [35]. While the aforementioned study investigated how physical characteristics alter a dogs perceived personality, the current study aimed to determine if human induced physical characteristics in dogs negatively impact how humans perceive the dog. This distinction is important as human induced changes may negatively affect the perception and subsequently treatment of the individual animal.

Many of the traits that were perceived differently are ones that have been shown to predict both adoptability and relinquishment [36,37]. Reasons cited in support of ear cropping include supporting the appearance of fierceness or aggressiveness [38]; results of the current study support this perception. Anecdotally we see this supported in society in articles such as one entitled “11 riskiest dog breeds for homeowners and renters” [39], published by Forbes magazine in 2012 (Jersey City, NJ) where half of the dogs listed are traditionally tail docked and/or ear cropped breeds (Pit Bulls, Staffordshire terriers, Doberman Pinscher, Rottweiler, Great Dane, and Presa Canario). Interestingly the Forbes article also mentions that in the case of these 11 breeds, home insurance rates may increase or in some cases coverage may be denied.

Natural dogs were also perceived by the participants in our study to be more playful and attractive than modified dogs. Playfulness is an important trait when determining adoptability [37] and frequently a trait cited by owners as important when making the decision of which dog breed to buy [40]. This suggests that while the dog breeds used in this study are popular, they are not perceived to possess characteristics desired by owners (ie playfulness, attractiveness) and instead possess traits that typically result in relinquishment (ie aggression). The fact that the participants perceived the modified dogs to be less attractive than natural dogs is of interest and contradicts the reasons given by some that tail docking and ear cropping is needed; specifically, when argued by breeders that these procedures ensure the integrity and beauty of the dog breed [12]. Questions remain as to why these breeds are popular and if greater awareness that these dogs had undergone surgery to alter the tails and ears would negatively affect this popularity.

Experiment 3.

To our knowledge this is the first study to provide evidence that physically altered pets affect the perceived personality and behavioural characteristics of their human owners. Aggression and playfulness were two of the traits used in Experiment 2 when assessing perception of dogs. In Experiment 2 the modified dogs were seen as less playful and more aggressive, which was similarly perceived in owners. This suggests that some behavioural traits perceived by participants in dogs are then reflected in their owners. This result supports the line of research that owners resemble their pets on some level [41]. In fact, studies have shown that participants can match dogs with their owners based on static images [42]. Therefore, increasing a dogs’ perceived aggressiveness by performing ear cropping and tail docking could in turn increase perceived aggressiveness in the owner which subsequently has the ability to affect human interactions. Furthermore, owners of modified dogs were perceived as less warm than owners of natural dogs. There is evidence to suggest that warmth is judged automatically, before competence, as whether a person appears to be friendly or trustworthy is more evolutionarily important than if they have the ability to act on these traits [43]. For example, viewing a person as more warm will more likely result in your desire to befriend the person or more simply approach the person than a person’s competence. In relation to the current study, this theory suggests that an owner of a modified dog appears more aggressive and less warm, resulting in an appearance that is less approachable than owners of a natural dog. Findings such as this that involve perception differences in personality are not exclusive to companion animals, in fact research has shown different houses and cars change perception of different gender roles and social status [44]. This is in line with a study by Wells and Perrine (2001) which found that a college professor with a dog or cat in their office was perceived as friendlier than if there was no animal [45].

Owners of a modified dog were also perceived as being more narcissistic than owners of a natural dog. Narcissism is described as “excessive self-admiration and feelings of superiority” [46] and narcissistic tendencies in humans having been linked to greater chances of social conflicts [47]. Taken together with the warmth and aggression results, it could be suggested that owners of modified dogs have a greater risk of social conflicts, human interaction complications and decreased approachability than owners of natural dogs.