Dog movie stars and dog breed popularity

A new research I co-authored with Stefano Ghirlanda and Hal Herzog has just been published in PLOS ONE (the paper is open access and can be found here). In this paper we continue our analysis of dog breeds popularity as a particularly interesting (and data-rich) cultural domain. We had already shown that the choice of which puppy one buys seems largely driven by fashion, i.e. social influence, more than by functional considerations (see my post from last year). Now we looked explicitly at one source of social influence, i.e. movies featuring dogs.

We found that indeed there is a strong effect of movies on the popularity of dog breeds. While this is not probably a shocking result, it is quite interesting to have precise quantitative data. We used the AKC database, totalling over 65 million dog registrations from 1926 to 2005, and analysed a total of 87 movies featuring dogs. The impact of movies has been large. We found, for example, that movies have an influence that can last up to 10 years from the initial release. The 10 movies with the strongest 10-years effect are associated with 800,000 more registrations in the AKC then what would have been expected from pre-release trends. A striking example is the 1959 Disney movie The Shaggy Dog. The registrations of Old English Sheepdogs were stable on around 100 dogs per year in the ten years preceding the release of the movie. In 1969 only, ten years after, 4,226 Old English Sheepdogs were registered.

We also found that the more a movie was successful (we estimated the number of viewers from the opening weekend earnings) the more impacted on the popularity of the breeds of the dog featured. Another interesting finding is that the influence of movies has decreased during the century. Earlier movies are in general associated with larger trend changes than later movies. This suggests that movies – perhaps because of an increased competition with other media, such as television, and, more recently, the internet – have gradually lost their influence on pop-culture.

Stefano made a nice figure showing some of the trends (click on it to see a larger version). Both the figure (here) and the data (here) are publicly available on


Together with our previous results, which showed that behavioural characteristics, longevity, or health were not correlated with breeds popularity, this new analysis provide a quite clear picture: we do not choose, on average, dogs because they are more healthy or, for example, trainable, but because we see them in the neighbours garden, or in the last blockbuster. Why this is not bad per se (copying what others do is a quite effective strategy in many situations) is definitely bad for dogs. The only feature that we found to positively correlate with popularity is indeed the presence of genetic diseases. Of course this does not mean that dog owners actively look for breeds with genetic diseases, but, as a minimum, that they do not keep this in consideration when choosing a puppy and, more worryingly, that the huge differences in popularity and the rapid increases of some breeds provoke over-breeding which results, in turn, in an increase of genetic disorders. My take-home message here is: don’t follow fashions when choosing a puppy!

Now a couple of more cultural-evolution related questions. First: how important is how the dog is presented in a movie for the effect on the popularity of the breed? We excluded few movies in which the dog was clearly a negative character (Cujo, for example) but we did not analyse in detail this issue. My feeling is that is not so important. While our data end in 2005, the AKC provides the rankings for more recent years. Hal noted the steady increase of French bulldogs (they were at the 54th position in 2003, and at the 11th last year). It happens that in a famous scene of the hugely popular movie The Hangover, Mike Tyson holds in his arm a French bulldog (see the video below from around 1:30). Since the movie is from 2009 (and we do not have the data…) is not clear whether the movie had an influence on the increase on popularity or if it is the other way around (i.e. the authors capitalised on the growing popularity of the breed and used it for the movie), but the dog is not more than a prop in the scene in question. The idea is that the mere presence of a dog in a popular movie makes it accessible and that, as features of different breeds are, in a sense, neutral (see below), a simple advantage in accessibility generates a cascade of effects (e.g. people will talk about that breed more than about other breeds) that may greatly influence popularity.

(the case of French bulldogs is also relevant for the previous point, as French bulldogs carry – in Hal’s words – a huge load of genetic disorders)

Second: does this result suggest that we are copy-machines, easily influenceable by evil Hollywood’s producers? I do not think so. As I mentioned above I consider the choice of a breed as being, by and large, neutral. This does not mean that all breeds are equal (of course they are not). However, given the choice of owning a dog (this, I think, is a non-neutral choice. Would be interesting to see whether movies influences the total number of dogs in time), the features of different breeds can be reasonably adapted to one’s own habits (or the other way around) so that the choice has, in the majority of cases, not enormous effects on the owners. Many people that are buying French bulldogs now would have probably bought poodles fifty years ago. Something similar happens, for example, for baby names (of course they are different; yes, some of them may have an effect on your life [but see here], but, in the majority of cases, being called Alberto or Stefano does not make much difference). For this kind of cultural traits I would indeed expect social influence and media having a strong effect on popularity, but less for traits that implies more important outcomes. We are not blind copy-machines, but selective copy-machines.


Ghirlanda S, Acerbi A, Herzog H (2014) Dog Movie Stars and Dog Breed Popularity: A Case study on Media Influence on Choice. PLoS ONE 9(9): e106565

Fashion vs. Function in Cultural Evolution: The Case of Dog Breed Popularity

The dynamics of dog breeds popularity have been recently used to test various assumptions of models of cultural evolution. Bentley et al. (Random drift and large shifts in popularity of dog breeds) found that the cumulative distribution of breeds popularity (i.e. how many dogs of each breed have been registered overall – in a period covering years from 1946 to 2001) roughly follows a power-law, meaning that very few breeds totalised the great majority of the registrations, and the great majority of breeds totalised proportionally very few registrations. Power-laws are ubiquitous in natural (the distribution of earthquakes magnitude) and socio-cultural (the distribution of wealth, the frequency of words in books, etc.) phenomena, and Bentley et al. showed that, for socio-cultural phenomena, these distributions can be produced by a simple “neutral” model of cultural evolution, which assumes that individuals just copy randomly cultural traits (dogs, in the specific case) from each other.

Subsequently, together with Stefano Ghirlanda and Magnus Enquist (The logic of fashion cycles), we used the same data focusing on another feature of dog breeds popularity, i.e. the fact that there is a correlation between the speed of increase in popularity of a breed and the speed of decrease: dogs that become quickly popular tend also to become quickly unpopular, and vice-versa (see the Rottweiler example below, many others here). To explain this feature – also found for baby names – we proposed a slightly more complicated model of cultural evolution, in which individuals may copy from each other not only cultural traits (the dogs) but also preferences for cultural traits (“I love Dalmatians!”). One of the property of this model is that individuals with low preferences for popular cultural traits tend to be better “influencers” (this is quite counterintuitive and, I think,  interesting – you can have a look here), so that, in the model, when a cultural trait becomes quickly popular, preferences for this cultural traits also become quickly negative, generating the correlation we found in the data.


Both models, however, assume that what drives the popularity of dog breeds is social influence (“fashion”). This is paradoxical: given that people presumably ponder their choice when deciding to have a pet, one would expect that features of breeds (“function”) would be more important in this decision. We just published a paper in which we take on this question. We used data on longevity, health, and behavioural characteristics of breeds (such as aggressivity, trainability, attachment, etc.) and correlated them with various popularity measures (speed of increase and decrease, total popularity, and volatility) to see which features were influencing more the popularity. The answer? None!

A part of taking a clear side in the debate whether to publish or not negative results, I think that there are some interesting conclusions from our analysis. Either social influence can indeed be, at least in some domains, a “blind” force that almost autonomously generates cultural dynamics, or – as I now prefer to think – it is tricky to recognise, from population level data, biases acting at individual level. This seems to me a quite interesting problem for people studying cultural evolution.


Acerbi A, Ghirlanda S, Enquist M (2012) The Logic of Fashion cycles. PLoS ONE  7(3): e32541

Berger J, Le Mens G (2009) How adoption speed affects the abandonment of cultural tastes, PNAS 106(20): 8146–8150

Herzog H, Bentley RA, Hahn MA (2004) Random drift and large shifts in popularity of dog breeds. Proceedings of the Royal Society B 271: S353–S356

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): e74770.