Are Big Dogs Really Smarter than Small Dogs?
It's highly unlikely because there are many different types of canine smarts.
Posted February 3, 2019
"My big dog often behaves as if he's dumb as a post, but my small dog is an Einstein."
"Size doesn't matter. My big and small dogs are smart on some tasks and not so smart on others."
"Molly, my tiny little mix, outshines Toby, my big mix, all of the time. Molly has Toby around her fingers or paws, and can easily manipulate her to steal her food, not once, but all the time."
"That's a silly question. It depends on the individual dog and the task they're asked to perform. Of the numerous dogs I've lived with of all sizes, I could never see any direct relationship between how big or small they were and how smart they were."
"There are many different types of intelligence or 'smarts' so this really is too general a question."
"It depends on what you want the dog to do."
The quotes above are some responses from people at a local dog park when I asked them, "Do you think big dogs are smarter than small dogs?" They reflect almost all of the responses I gathered.
A recent essay called "Are Big Dogs Smarter Than Small Dogs?" by Psychology Today writer and author Dr. Stanley Coren caught my eye as it did for many others. In his piece, which is available for free online, Dr. Coren nicely summarizes a study by Dr. Daniel J. Horschler and a group of distinguished researchers published in the journal Animal Cognition titled "Absolute brain size predicts dog breed differences in executive function" for which only the abstract is currently available for free online.1 In his discussion of the research, Dr. Coren notes that dogs are a good species on which to study relationships between body size, brain size, and what he calls "mental ability." He also summarizes what he discovered when he looked at the relationship between "working and obedience intelligence" among different dog breeds, namely, "...in the top 20% of the dogs ranked for their intelligence, there was only one small toy breed (the Papillon, which is a roughly 8-pound [3.6 kg] toy spaniel)."
The data in the original research paper come from citizen scientists who were given instructions on how to perform 10 different tests to learn more about "executive function," defined by the researchers as "a suite of cognitive abilities involved in behavioral control, including working memory and inhibition." Data were collected for 7000 purebred dogs representing 74 breeds. It's interesting to note that in the research paper the words "smart" and "intelligent" don't appear.
Along these lines, Dr. Coren notes, "Many of the tests are only marginally related to what most researchers tend to view as aspects of intelligence (such as whether a dog imitates the owner when he yawns). However, one measure that they used is definitely a component of mental ability that is often tested by researchers interested in canine intelligence, and that is 'delayed memory.' In this case, the memory test consists of having the owner place a treat under one of two cups in full view of the dog. Next the owner waits for 60, 90, 120 or 150 seconds before releasing the dog. This is done for four trials and the data consists of whether or not the dog goes to the correct (baited) cup. Data were collected on 1888 dogs with unambiguous results, namely, "There was a clear trend indicating that larger dogs were able to accurately remember over a longer period of time than were their smaller counterparts." So, all in all, "larger brain sizes in dogs are associated with better cognitive performance" and "Larger dogs exhibited better cognitive and mental performance."
In a previous essay called "Can a Dog's Size Predict Its Intelligence?" in which individuals of 128 breeds were studied concerning "working and obedience intelligence," Dr. Coren discovered that very few toy dogs (averaging 2-9 pounds) or members of giant breeds (averaging 85-120 or more pounds) ranked high in obedience related intelligence, or well a dog performs different obedience exercises. This is an example of "stabilizing selection," "a type of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value" (for more on stabilizing selection please see). What this means is that outlying individuals are selected against and "average" individuals are more adapted than those "extreme" individuals who fall in either end of the normal distribution. He goes on to write, "This would be consistent with research showing that dogs whose head shape was relatively flat or relatively elongated in comparison to the average head shape of dogs seem to have lower intelligence. (Click here for more about that.) Apparently this same principle seems to hold for dog size: Dogs at the extremes—either excessively small or excessively large compared to the overall population of dogs—seem to be less well adapted in terms of intelligence. Thus the medium-to-large dogs would seem to be the most intelligent, at least in terms of the kind of intelligence that determines how well a dog will perform obedience exercises."
An essay called "Are Big Dogs Smarter Than Small Dogs? Size May Actually Predict Intelligence" by Allegra Ringo nicely summarizes Dr. Coren's earlier Psychology Today essay. She rightly cautions us about concluding that brain size plays a large role in a dog's intelligence. Ms. Ringo concludes, "...many factors in a dog's life, both genetic and environmental, could contribute to its intelligence. We don't have nearly enough evidence to definitively say that size affects intelligence one way or the other." I agree, and of course, each dog needs to be viewed as the individual they are, because there are large within-species (infraspecific) differences among dogs, including littermates and siblings. Simply put, there is no "the dog" or the "canine mind." (See "Let's Give Dogs a Break by Distinguishing Myths From Facts" and "The Minds and Hearts of Dogs: Facts, Myths, and In-Betweens.")
What is the relationship between executive function and intelligence?
As I wrote above, it's interesting to note that in the research paper the words "smart' and "intelligent" don't appear. To learn more about what the researchers were studying, I wanted to learn more about the meaning of the phrase "executive function" and a web search came up with numerous hits. In an easy-to-read essay by Jackie Stachel titled "IQ and Executive Function Skills: The Engine and the Fuel," I found what I was looking for. She writes, "Essentially, Executive Function skills help us be productive. And that’s the distinction between Executive Function skills and intellect. A person with a high IQ can be capable of understanding or discussing complex concepts, but be nearly incapable of producing an essay, completing a set of problems, or finishing a research paper. Why? It’s not because he isn’t smart enough, it’s because he can’t effectively marshall his efforts toward a specific end result. Think of IQ as the engine in a car and Executive Function skills as the oil, fuel, belts and hoses that make it run effectively. That perfectly restored 1969 Pontiac GTO with a 330 horsepower engine has plenty of potential to cruise down the highway on a sunny Saturday, but see how far you get with faulty spark plug wires."
Ms. Stachel also writes, "Now you see why we, as Executive Function coaches, don’t put our emphasis on being 'smart.'” Her essay and others clarified the difference between executive function and intelligence, and it's clear they're not synonyms.
So, are big dogs really smarter than small dogs?
In a 2013 interview in Scientific American, Dr. Brian Hare, co-author with Vanessa Woods of The Genius of Dogs and founder of the Duke Canine Cognition Center, was asked, “What is the biggest misconception people have about the dog mind?” “That there are ‘smart’ dogs and ‘dumb’ dogs,” replied Dr. Hare. “There’s still this throwback to a unidimensional version of intelligence, as though there is only one type of intelligence that you either have more or less of.”
Dr. Hare, who is also a co-author on the research paper about which I'm writing, is right on the mark. And it makes sense why the researchers didn't use the words "smart" or "intelligent" when they wrote about executive function. There are multiple intelligences in dogs and other animals, and individual differences are to be expected. Differences are the rule rather than the exception. Research has shown that many different variables can influence a dog’s performance in laboratory settings, and I often wonder how the data collected in controlled experiments transfer to dogs in real life, as dogs run around at dog parks and other venues and cope with changing social contexts and physical environs.
In Canine Confidential: Why Dogs Do What They Do I stress that the word “intelligence” generally refers to the ability of an individual to acquire knowledge and to use it to adapt to different situations and do what’s needed to accomplish various tasks and to survive. A friend of mine once told me about the free-running dogs she knew in a small town in Mexico who were cleverly street-smart and could survive in difficult conditions, but they didn’t listen to humans all that well. Some were skilled at finding and snatching food and avoiding dogcatchers, unfriendly dogs, and people. Some were good at “playing” humans for food, whereas others weren’t. Conversely, I’ve known some intelligent, crafty, and adaptable dogs who weren’t street-smart and likely couldn’t make it in such an environment. However, a few with whom I shared my home could easily steal my food and that of the other resident dog in a heartbeat, without either of us knowing what was happening.
Which dogs were “smarter” and which “dumber?” Neither, of course. Relatively speaking, these dogs were equally intelligent, but they adapted their smarts to different circumstances. Outside those contexts, they might appear quite “dumb” to us. I’ve lived with and met enough dogs to know that saying one is smarter than another is usually a mischaracterization of who, as individuals, they truly are.
To sum up, neither the researchers nor Dr. Coren in either of his essays, as far as I can tell, really answer the question he posed in his essay, specifically, "Are Big Dogs Smarter Than Small Dogs?" Perhaps on one or a few tasks they were, but many people who wrote to me asked how robust is the relationship between brain size and "smartness" or "intelligence," noting that the researchers really only answered questions about the relationship between the size of dogs and executive function. And, the smattering of answers to the question with which I began this essay, "Do you think big dogs are smarter than small dogs?" along with many other responses shows that people don't really see any obvious or direct relationship between the size of a dog and how smart they are. Some dogs are "smart" when asked to learn one ask, and not so smart when asked to learn another.
In addition to being interested in possible relationships between body size, brain size, and cognitive and emotional capacities, I'm also interested in the general question of how dogs of different sizes would do if and when humans disappear and they have to fend for themselves. Of course, there are many different factors that need to be considered in how dogs will do without us, but it's not at all clear if large or small dogs will be better, although many people quickly answer something like, "Big dogs will survive better than small dogs because they'll be able to compete for food and other resources." However, this isn't necessarily so, and a dog's individual characteristics will surely play significant roles. (See "How Will Dogs Reshape Nature Without Humans to Control Them? and "As Dogs Go Wild in a World Without Us, How Might They Cope?" for more discussion.)
So, are big dogs really smarter than small dogs? We really don't know, but it's highly unlikely. There are many different types of intelligence among human and nonhuman animals, including dogs, and much more research is needed before small dogs are written off as being "not so bright." And, of course, individual differences among dogs of all sizes need to be taken into account before any beliefs or grand pronouncements about possible relationships between size and smarts are accepted as facts.
1The abstract for the original research paper reads, "Large-scale phylogenetic studies of animal cognition have revealed robust links between absolute brain volume and species differences in executive function. However, past comparative samples have been composed largely of primates, which are characterized by evolutionarily derived neural scaling rules. Therefore, it is currently unknown whether positive associations between brain volume and executive function reflect a broad-scale evolutionary phenomenon, or alternatively, a unique consequence of primate brain evolution. Domestic dogs provide a powerful opportunity for investigating this question due to their close genetic relatedness, but vast intraspecific variation. Using citizen science data on more than 7000 purebred dogs from 74 breeds, and controlling for genetic relatedness between breeds, we identify strong relationships between estimated absolute brain weight and breed differences in cognition. Specifically, larger-brained breeds performed significantly better on measures of short-term memory and self-control. However, the relationships between estimated brain weight and other cognitive measures varied widely, supporting domain-specific accounts of cognitive evolution. Our results suggest that evolutionary increases in brain size are positively associated with taxonomic differences in executive function, even in the absence of primate-like neuroanatomy. These findings also suggest that variation between dog breeds may present a powerful model for investigating correlated changes in neuroanatomy and cognition among closely related taxa."
Daniel J. Horschler, Brian Hare, Josep Call, Juliane Kaminski, Ádám Miklósi and Evan L. MacLean (2019). Absolute brain size predicts dog breed differences in executive function. Animal Cognition.