25 September 2013

Why Are Some Breeds of Dog More Popular Than Others?

Why are some breeds of dog more popular than others, and do different breeds really have different personalities? The answer to the second question is yes.
Photo: bikeriderlondon/Shutterstock
There are so many breeds of dog, it can be hard to choose which one you'd like most. Some are always popular, while other breeds rise or fall in popularity.  A new study by Stefano Ghirlanda et al 2013 investigates whether changes in the most popular breeds over the years reflect personality characteristics, health, or fashion.

We think of different breeds as having different temperaments, such as the “friendly and gentle, but also alert and outgoing” Siberian Husky, the “alert, lively, active, keen” Russell Terrier “with a very intelligent expression,” or the “calm, confident and courageous” Rottweiler. The first question the scientists asked was, is this true?

For their answer, they turned to the C-BARQ, a standardized questionnaire about doggie behaviour and temperament. It has 14 scales including trainability, separation-related behaviour problems, energy levels and so on, and has been completed for over 12,000 dogs. They narrowed it down to a list of eighty different breeds, with data from a total of more than 8,000 dogs.

The results showed that different breeds do have different personalities. The results for the top ten breeds are shown in the figure below, with each coloured slice of pie representing a different C-BARQ scale. The most interesting one is that of trainability, which is shown by the green slice in the top left. Many of the top breeds score highly for trainability. 

The Golden Retriever scores very high on trainability, and very low on everything else (mainly problem behaviours). Is this the perfect breed of dog?! The Poodle and Labrador Retriever are also highly trainable, with few problem behaviours.

Several of the top ten dog breeds have low scores for trainability, including the Chihuahua, the Miniature Schnauzer, and the Dachshund. Chihuahuas score highly on several problem behaviours including fear of strangers, fear of dogs, dog rivalry and touch sensitivity. The Miniature Schnauzer has high scores for chasing, dog aggression and excitability, amongst others, while the Dachshund has a tendency for dog aggression, stranger aggression and separation problems.

Despite this, they are very popular breeds, suggesting that other aspects are important in people's choices. And of course, part of the reason they exhibit these problems could be because small dogs tend to be treated differently (Arhant et al 2010).

C-BARQ subscales for the top ten dog breeds in the US
Source: PLoS One

But personality isn’t everything. Some breeds of dog live longer than others and have fewer health problems. For data on this, the researchers turned to previously published papers which rated breeds for longevity and health. The surveys showed an average lifespan of 11.45 years. Variability was large, ranging from 6.3 to 14.3 years. In general, large companion dogs have a shorter longevity (8.5 years) than medium (10 years) or small companion dogs (12.5 years).

They got information about the popularity of different breeds from the American Kennel Club, which has data going back to 1926 for over fifty million dogs. This study considered data from 1926 to 2005, and for the eighty breeds for which the behaviour and health data was available.

In 1926, the most popular breed of dog in the US was the German Shepherd, still very popular today. The Boston Terrier, Chow Chow, Fox Terrier and Pekingese round out the top five for that year.

There was no correlation between breed temperament and popularity. Nor was there any correlation between longevity and popularity. However, there was a significant correlation between the popularity of a dog breed and the number of inherited health disorders that breed tends to suffer from. In other words, the more popular breeds tend to have more health problems. The authors say this suggests "health considerations have been secondary in the decision to acquire dogs as well as in dog breeding practices."

They also found that between 1996 and 2005, the breeds with the most health problems declined in popularity. This could be because of increasing awareness of the health problems that go with those breeds. 

The authors say that “If anything, our results suggest that breeds can become popular despite problematic behaviour, rather than because of good behaviour.” It seems that behaviour and health are not the main reasons why people choose particular breeds of dog; perhaps fashion and looks are more compelling.

What breed(s) of dog do you have, and why did you choose them?

Arhant, C., Bubbna-Lititz, H., Bartels, A., Futschik, A., & Troxler, J. (2010). Behaviour of smaller and larger dogs: Effects of training methods, inconsistency of owner behaviour and level of engagement in activities with the dog. Applied Animal Behaviour Science, 123, 131-142 DOI: 10.1016/j.applanim.2010.01.003
Ghirlanda S, Acerbi A, Herzog H, & Serpell JA (2013). Fashion vs. Function in Cultural Evolution: The Case of Dog Breed Popularity. PloS one, 8 (9) PMID: 24040341

18 September 2013

Perceiving Emotion in Babies and Dogs

A playful boxer dog with open mouth and flapping earsDarwin suggested that some human emotional expressions could have their origins in the facial expressions of other animals, including primates and dogs. If so, there would be similarities in the way people process emotional faces across these different species. While most research has focussed on other primates, a paper just published in PLoS One by Annett Schirmer et al (National University of Singapore) investigates whether or not there are similarities in processing facial expressions in human infants and dogs.

The study asked sixty-four participants, half of whom were dog-owners, to take part in a series of tests. The experiment included both implicit and explicit tests of emotional processing. The explicit tests asked people to look at photographs and rate the emotion being expressed. For the implicit tests, people were shown a photograph and then a set of letters on a computer screen; they had to decide if the letters were a word or not. 

The words were either positive or negative. The idea is that even though the photograph is not related to the word task, if people process the emotion then it will affect their ratings. For example, if the photograph is of a positive emotion and then the word HAPPY pops up, it will take people slightly less time to decide this is a word than if the photograph had been of a sad face. This is known as a priming effect.

The researchers looked at positive and negative facial expressions, so they refer to it as affect, because they have not specified which emotion it is.

Photographs of dogs and babies were taken especially for the experiment. Dogs were recruited at a park. For the positive affect photo, they were given food or a toy, depending on what the owner said they would prefer. For the negative affect photo, they were put in a crate for five minutes while the owner went away.

Baby photographs were taken in the lab. In order to capture pictures of positive affect, the babies were given a toy. For photos of negative affect, the parent was asked to leave the room so the baby was alone with the experimenter. In some cases this did not upset the baby, in which case the experimenter hid from them. In all cases, for babies and dogs, the duration of the negative affect was kept short.

The photographs were touched up as necessary, e.g. to account for movement or to remove the crate bars from the image. Full-face photos were used, and cropped images of the eyes were also used for the explicit task.

Photos of the faces of dogs and babies used in the experiment
Images used in the study, showing baseline (neutral), positive and negative affect. Source: PLoS One
The results showed that there was a priming effect for both the human and dog faces. In other words, people were influenced by the positive or negative affect in the photo. While this has been previously shown for human faces, it is the first time it has been shown for affective photos of dogs. It suggests that people automatically process affect in both dogs and humans.

In the explicit processing task, participants were able to recognize positive and negative affect in both humans and dogs. Ownership of a dog did not have an effect on people’s ratings of the dog images.

People responded more accurately to photos of the full face than the cropped image of the eyes, for both humans and dogs. The results also suggest a similarity in the human and canine expression of sadness via the eyes, but not happiness.

There were gender differences in both the explicit and implicit tasks. While both men and women recognized affect in a dog’s face, women were better at it than men, and women dog owners were better than those who did not own dogs. It is no surprise to find gender differences, since other studies have suggested that women are more sensitive to emotional expression than men. The fact that dog ownership makes a difference for women, but not men, suggests women dog owners are more attuned to canine expressions than their male counterparts. There are several possible reasons for this, including differences in the experience of owning a dog (e.g. perhaps women take more responsibility for the dog).

People were more sensitive to human emotional expressions than to canine ones. Dog ownership did not affect this, but experience with dogs did, since some non-dog owners had no experience with dogs at all. This is in line with a study by Michele Wan, which found that although people found it easy to recognize happiness in dogs, experience was important when it came to recognizing fear.

The authors say their results show that “humans recognize positive and negative affect in the facial behavior of dogs and that they can do so without having ever interacted with a dog. Additionally, a number of similarities were revealed between the processing of human and dog expressions.”

This would be expected for non-human primates. Extending it to dogs is a significant step. This supports the idea of an overlap in emotional expressions in primates and canines due to continuity of evolution.

Do you find it easy to recognize positive and negative emotions in your pets?

Schirmer A, Seow CS, & Penney TB (2013). Humans process dog and human facial affect in similar ways. PloS one, 8 (9) PMID: 24023954  
Wan M, Bolger N, & Champagne FA (2012). Human perception of fear in dogs varies according to experience with dogs. PloS one, 7 (12) PMID: 23284765

11 September 2013

Can Dogs Smell Quantity of Food?

Can dogs tell how much food there is just by using their nose?

An English boxer sniffs an overflowing bowl of kibble

We all know dogs’ noses are amazing. From careful attention to the pee-points on their walk, to working as drug or explosive detection dogs, it’s clear dogs have an excellent sense of smell. So it’s surprising that most studies of olfaction are about specially trained dogs, and less attention has been paid to the average pet dog. A paper in press in the journal Learning and Motivation, by Alexandra Horowitz, Julie Hecht and Alexandra Dedrick, sets out to change all that by asking, can dogs smell whether a closed plate contains a small or large quantity of food?

The research is based on a study of canine preferences by Prato-Previde et al in 2008. They found that when dogs could see two plates, one with a small amount of food and the other with a large amount of food, they preferred the plate with more food. No surprises there! However, when given the same choice but with their owners making a fuss over the plate with a small amount of food, most dogs changed their preference and went for the plate their owner was interested in.

The study by Horowitz et al replicates this paper, but using closed plates so that dogs could not see the quantity of food; instead they had to rely on their sense of smell. One plate had only one piece of hot dog whereas the other had five pieces. The plates were prepared beforehand and ‘closed’ by putting another plate on top, so the contents were not visible. They were then given to the experimenter so that she did not know which plate had the most food. Pieces of dried liver were used for one participant who did not like hot dog.

Sixty-nine pet dogs took part, although five were excluded from the results (e.g. because they always chose the plate on one particular side). To ensure they would be interested in food, their owners did not feed them during the three hours prior to the experiment. 

The study took place in a small empty room, either at the University or at a doggy daycare. To get the dog ‘warmed up’, they were shown a plate on the floor with a piece of hot dog, and allowed to take it. There were three experimental conditions, and dogs took part in each one in turn (only fifty-three dogs did condition two). The sessions were video-recorded for later analysis.

In the first condition, the owner sat on a chair with their eyes shut. They held the dog by its collar. The experimenter approached with two closed plates, got the dog’s attention, and allowed it to sniff each plate for about three seconds. Then she put the plates on the floor and turned her back.  The owner released the dog. When it approached one of the plates, the experimenter turned around and threw a piece of hot dog as a reward. 

The second condition was very similar, except the owner’s place was taken by one of the scientists. The plates were prepared as before, and presented by the experimenter. Then, once she had placed both plates on the floor, the owner picked up the plate with the smaller item of food and said to her dog something like “Oh boy, this is good food, yummy!”.  Then they put the plate back, went and stood next to their dog, and the dog was released. As in the first condition, when the dog approached a plate it was given a piece of hot dog.

Although 61% of the dogs approached the plate with the large amount of food first, it wasn’t significantly different from chance.

However, when the owner talked happily about the plate with a small amount of food, the dogs’ preference changed. Dogs were significantly more likely to choose the smaller amount when their owner was enthusiastic about this plate.

Forty-four of the dogs paid more attention to one plate than the other; amongst these dogs, it was the plate containing more food that received significantly more attention. This suggests they could detect something, even though it didn't influence their choices.

The third and final condition investigated the effects of adding a scent to the plate with the most food. The scents were from products aimed at the pet market, and hence safe for dogs: mint from a spray designed to improve the smell of a dog’s breath, lavender from a doggy deodorizing spray, and distilled vinegar since this might be used in cleaning. This time the plates were open, so the dog could see the quantities of food, but otherwise it was the same as the first condition. 

Did the addition of a strong scent to the plate with the large amount of food change a dog’s preference? You bet! 64% of the dogs now preferred the small, unadulterated, amount of food for at least one of the smells.  There were individual differences between the dogs as to which of the smells they did not seem to like.

The design of this experiment is really nice because great care was taken to ensure there were no biases that might affect the results. The authors also checked that there was no difference between simultaneous versus alternate presentation of the two plates.

Whether dogs went to the smaller- or larger-food plate first, they were rewarded with one piece of hot dog. It would be really interesting to see a future study in which the size of the reward matched the choice of the plate, to see if the dog would learn over time which choice earned the larger reward.

So, contrary to an earlier study based on sight, dogs could not detect the larger amount of food by smell alone. However, dogs were influenced by their owners when they made a fuss of the smaller-food plate. Adding a strong scent to one of the plates also caused dogs to change their preference. This study is a fascinating step in our understanding of the olfactory abilities of ordinary pet dogs.

What is your dog’s sense of smell like?

Horowitz, A., Hecht, J., & Dedrick, A. (2013). Smelling more or less: Investigating the olfactory experience of the domestic dog. Learning and Motivation, (in press)  
Prato-Previde E, Marshall-Pescini S, & Valsecchi P (2008). Is your choice my choice? The owners' effect on pet dogs' (Canis lupus familiaris) performance in a food choice task. Animal cognition, 11 (1), 167-74 PMID: 17641921

04 September 2013

How Do Dogs Interact With an Unidentified Moving Object?

A portrait of a happy leonberger with beautiful brown eyes
One time when I took my dog for a walk, someone was playing with a radio-controlled car on the road. This was Very Exciting (actually most things in life are Very Exciting!). I asked him to heel as we walked past it, but he would have preferred to investigate the car. How do dogs interact with things like this, and does it change if the object moves in an apparently social way?

Robots have been used in studies with various species as a way of experimentally testing the rules of communication. Perhaps the most interesting for dog lovers is Leaver and Reimchen’s (2008) study in which off-leash dogs interacted with a dog-like robot with one of four different possible tails: short and still, short and wagging, long and still, or long and wagging. With the long tail, dogs were more likely to approach if it was wagging rather than still, but there was no difference between the two short tail conditions.

A new study by lead author Anna Gergeley et al in Hungary tests whether the actions of a mechanical object affect how a dog responds. They used a radio-controlled car as an Unidentified Moving Object. In one condition, the car (operated by an experimenter) always followed a fixed route in the lab. They called this the Mechanical UMO. In another condition, the experimenter made the car act as if it was social, by making it move in response to the dog looking at it (Social UMO). The car also had eyes drawn on the windscreen. In a third condition, a human played the role of a Mechanical Human by wearing sunglasses (so as not to make eye contact) and following exactly the route of the fixed UMO in a mechanical way.

The photograph below shows a) Mechanical UMO; b) Social UMO; c) Mechanical Human.

Forty-seven pet dogs took part in the study (a further three were recruited but had to be excluded due to anxiety). They were divided into three groups, and each dog took part in just one of the conditions. 

Source: PLoS One

After an initial warm-up, there was a set of trials which began with an experimenter placing food into one of three bowls in the room. The dog stayed by the owner at one end of the room. The Unidentified Moving Object or the Mechanical Human set off to move about the room, taking the food from the bowl and placing it in a cage where it was out of the dog’s reach.  Then the dog was released to explore for a fixed period of time, and then called back to the owner. The UMO or Mechanical Human began to move again, this time collecting the food from the cage and delivering it to the dog. An ingenious set-up with magnets allowed the UMO to move the food around.
The results showed that more dogs looked at the UMO in the Social condition than when it was Mechanical, or the Mechanical Human. This suggests that the behaviour of the item affects how dogs respond to it. The dogs also spent more time looking at the Mechanical UMO rather than the Mechanical Human, possibly because it was a novel item.

As in Leaver and Reimchen’s study, this shows that it is possible to test how dogs respond to apparently-communicative behaviour by using a mechanical object. Communication in the real world is messy, so experimental set-ups like this are sometimes very useful.

This study makes me wonder about the possibilities for hi-tech interactive dog toys. The electronics would have to be in a chew-proof housing, of course!

How does your dog (or cat) respond to a remote-controlled car?

Gergely, A., Petró, E., Topál, J., & Miklósi, A. (2013). What are you or who are you? The emergence of social interaction between dog and an Unidentified Moving Object (UMO) PLoS ONE  
Leaver, S.D.A., & Reimchen, T.E. (2008). Behavioural response of Canis familiaris to different tail lengths of a remotely-controlled, life-size dog replica Behaviour, 145 (3), 377-390

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