One of the easiest ways to start an argument among people who own dogs as pets is to raise the issue "Which is better, a purebred or a mixed-breed dog?" In such an argument the mixed-breed advocates are apt to bring up the topic of "hybrid vigor". This refers to the idea that mixed-breed dogs have fewer health problems because of a more diversified gene pool. While it is true that certain purebred dogs can show a number of physical problems which are genetically based, the jury is still out on whether mixed-breed dogs are healthier overall. Thus far the data suggests that mixed-breed dogs can inherit many of the problems associated with each of the breeds that goes into their makeup. So the general consensus seems to be that mixed-breed dogs are no more or less likely to have health issues than their purebred counterparts. However, what about behavioral differences?
In most countries mixed-breed dogs actually outnumber purebred dogs. For example, a national census showed that 53% of the dogs in the US are mixed breed (click here for more about this). Therefore it is a bit surprising to find that there are very few scientific studies contrasting the differences in personality and behavior between purebred and mixed breed dogs. Nonetheless many people seem to feel that the hybrid vigor argument carries over into the behavioral realm. An example of this comes from one of the PETA websites which claims, "Mixed-breed dogs are wonderful compared to purebred dogs who have a greater tendency to be nervous, neurotic and excitable." Unfortunately no supporting evidence for this statement was provided.
As usual, science eventually comes around to address issues that people find important or interesting. A new study by Hungarian researchers at Eötvös Loránd University in Budapest has just appeared in the journal PLOS One* and it looks at behavior differences between these two populations of dogs. The team of researchers consisted of Borbála Turcsán, Ádám Miklósi and Enikö Kubinyi from the Department of Ethology.
This was a really a pair of investigations which collected data from a very large sample of dogs — 7,700 purebred dogs representing more than 200 breeds and 7,691 mixed-breed dogs. The data was collected in an interesting way. Dog owners filled in an online questionnaire (in German) which was advertised in the "Dogs" magazine and also on the magazine's website. It was accompanied by a short article trying to stir up interest in owner participation, and was available for five months. To control for the effect of breed popularity in the purebred group (which might lead to an overwhelming number of dogs from a few popular breeds) a cutoff point was used to limit the number of dogs from any one breed to 60 in the first study and 37 for the second study.
As is typical in such large survey investigations, a lot of different variables were analyzed and some pretty high powered statistical techniques were used. In some cases the findings were reanalyzed in different ways to try to tease apart some detailed nuances of the behaviors. However, since the space that we have here is limited I will stick to the main effects and the highlights of the data.
To begin with there were personality differences between the two groups. The mixed-breed dogs were significantly less calm than the purebred dogs. Calmness is demonstrated by a dog who is cool-headed and emotionally balanced versus one who is anxious, or appears to be stressed.
The mixed breed dogs were also considerably less sociable toward other dogs. Sociability is shown in dogs which are judged to be friendly and willing to share toys as opposed to dogs which are apt to be quarrelsome and are rated as being bullying.
The mixed breed dogs were also more likely to show behavior problems. These include dogs that frequently pull on the leash, jump up on people, don't respond when called, show dominance behaviors and so forth.
Two other aspects of behavior were looked at. Purebred and mixed-breed dogs showed little or no differences in terms of their trainability. They were also similar in the personality trait called boldness (an assertive dog would be high on boldness while a fearful, awkward dog would be low).
The research team tried to discover why the differences between mixed-breed and purebred dogs existed. One possibility that they considered is that mixed-breed dogs are for the most part the result of random breeding rather than planned matings. Purebred dogs are usually subject to careful selective breeding. Even if breeders are most concerned about the appearance of their dogs, they also tend to pay attention to temperament. It is less likely that an ill-tempered and excitable dog with behavior problems will be bred. This is because, in part, that breeders know that this will not be good for the breed in general, and also because it is much more likely that a badly behaved dog will be returned to them by the purchaser. To the extent that this is true it means that the differences between mixed-breed dogs and purebreds could be, at least partially, attributed to genetic factors.
However the research team also found that there were a number of environmental factors having to do with the demographics of the dog owners and the way the dogs were reared which might have an effect. For example, mixed-breed dogs were more likely to be owned by women, and these women tended to be younger, with a lower level of education, and had less previous experience with dogs than the owners of purebred dogs.
Another factor was that mixed breed dogs tended to receive less formal training than purebred dogs. This is important because the amount of training affected how well the dog scored in terms of calmness and sociability and also dogs that have received training were reported to have fewer behavioral problems.
Mixed-breed dogs were also more likely to be the only dog in a household, and tended to be kept indoors most of the time. These dogs also tended to be brought into the household at an older age than were purebred dogs. This fact is important since the researchers found that dogs brought into the home at an age of less than 12 weeks were calmer overall.
A further interesting factor was that mixed-breed were more likely to be neutered. These investigators found that dogs which had been spayed or neutered will had lower scores in terms of their calmness and were more likely to show behavior problems. This is consistent with other research which shows that neutered dogs are more likely to be aggressive, fearful and excitable (click here for more about that).
Thus this research team concludes that there are real differences between mixed-breed and purebred dogs in terms of their personality and behavior. They also suggest that these differences are not simply genetic but also may reflect the environment in which the dog is reared, the training is that the dog receives, and the characteristics of the dog's owners.
Stanley Coren is the author of many books including: Gods, Ghosts and Black Dogs; The Wisdom of Dogs; Do Dogs Dream? Born to Bark; The Modern Dog; Why Do Dogs Have Wet Noses? The Pawprints of History; How Dogs Think; How To Speak Dog; Why We Love the Dogs We Do; What Do Dogs Know? The Intelligence of Dogs; Why Does My Dog Act That Way? Understanding Dogs for Dummies; Sleep Thieves; The Left-hander Syndrome
Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission
* Data from: Borbála Turcsán, Ádám Miklósi and Enikö Kubinyi, (2017). Owner perceived differences between mixed-breed and purebred dogs. PLoS ONE 12(2): e0172720. doi:10.1371/journal.pone.0172720