In 1994 Dr. Stanley Coren wrote a landmark book, The Intelligence of Dogs, where he sampled the opinions of a large number of obedience judges on the trainability of different breeds of dogs (see Dr. Coren’s blog post from June 10, 2009 on our blog here). Dr. Coren identified the breeds that were most and those that were least trainable, and related this to the relative intelligence of the different dog breeds, at least as far as their general trainability went.
A recent article (Helton, W. F. 2009. Cephalic Index and Perceived Dog Trainability. Behavioural Processes 82:355-358) attempts to connect the shape of dogs’ heads to their trainability. By looking at the ratio of the width to the length of the skull (a cephalic index), dogs can be categorized as dolichocephalic (having a short skull width with respect to the length, as in Greyhounds), mesocephalic (having a medium width of the skull with respect to the length, as in Poodles), and brachycephalic (having a large skull width with respect to the length, as in Staffordshire Bull Terriers).
These groups of dogs differ in their morphological specializations. Dolichocephalic dogs are specialized for running, while brachycephalic dogs are more specialized for fighting.
Interestingly, the eye morphology of the two types of dogs differs. Brachycephalic dogs like the Staffordshire Bull Terrier have a lot of the retinal ganglions concentrated in a central area, like the human fovea, allowing them to focus better on single objects, such as other dogs they might need to fight. Dolichocephalic dogs like the Greyhound are like wolves in their retinal morphology. They have a visual streak of retinal ganglia, distributed like a line across the retina, allowing them to best see moving objects such as prey on the horizon rather than focus in detail on single objects. (for details, see McGreevy, P. et al. 2004. A strong correlation exists between the distribution of retinal ganglion cells and nose length in the dog. Brain, Behavior and Evolution 63: 13-22; DOI: 10.1159/000073756).
Curiously enough, the Helton article in Behavioural Processes finds that the breeds that are the most trainable are those that fit into the mesocephalic category, with neither a very long or a very short nose, and a skull width that is intermediate between narrow and wide. This includes breeds such as the Border Collie, Poodle, Labrador Retriever, and Golden Retriever.
What isn’t clear to me is why this should be so. The author of the article speculates that the mesocephalic brain shape represents a compromise between a brain adapted for running and a brain adapted for fighting. So, if this is true, then maybe the breeds in the other categories are so specialized that they don’t need to learn to do new things. They either run or they fight. But the dogs in the middle can’t run as fast and can’t fight as hard, so maybe they have to be more flexible in learning how to get by in the world.
And as long as I am speculating, let me take this a little bit further. If there really is a relationship between the shape of the skull and trainability, maybe we can use this as a way of predicting the trainability of mixed breeds. When we look at shelter dogs of mixed parentage where it isn’t obvious which breed contributed the most to the genetic makeup of the dog, maybe we can get an idea of how easy the dog is going to be to train from the shape of the skull.
In my book, all dogs are wonderful. Some just require more work than others. If we can predict how much work might have to go into training a mixed-breed dog, maybe there won’t be as many dogs returned at shelters.