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It's a fiercely debated topic. Which species is more intelligent - cats or dogs?

Animal lovers have their prejudices, and this is one they get really worked up about. Then just as the debate settles down, some new article comes along saying that the evidence points in a particular direction. And off we go again.

Is there a conclusive answer, or are we in fact asking the wrong questions? Following our diligent search to get to the bottom of the issue; we review the pros and cons of arguments presented in the past. Hopefully our neutral, unbiased study will conclusively prove, once and for all, that cats are the Einsteins of the pet world.

So what's the evidence? Errr …

There's a problem which sabotages the whole debate from the word 'go'. At present there is no such thing as a reliable test which can measure a cat's intelligence. Humans just can't understand the feline mind enough to measure its kilo-wattage. (The fact that we can’t understand how they think partly explains why many people have this deep fascination with cats.)

At least superficially, dogs are far more transparent. Given some training, most dogs will (at least temporarily) do as their owners want. But does that ready response to follow orders show intelligence?

Take a large empty box. Open it and order a dog to get in. Obediently the dog jumps in. This is because he was told to do so, and so he does despite the fact that it is an empty box with nothing interesting in it. But the dog is desperate to please his human, so in he goes.

Now try that with a cat. The cat won’t get into the box just because we want her to. Anyone who has ever had a cat knows there are only two ways to get that cat into the box. Either you shove a yowling protester in there by main force, or you persuade that cat to get into the box because it wants to.

The saying 'dogs have masters, cats have staff' has a basis in reality..

The box is just one example which illustrates the different behaviour of cats and dogs. But the assumption that the different behaviour is driven by higher or lower intelligence is questionable. It's more a matter of character.

Recently the dog IQ boosters have been getting the better of the academic debate, with articles in scientific journals suggesting that dogs are more intelligent than cats. So let us consider the science behind those claims.

In 2009, psychology lecturer Britta Osthaus and her colleagues set up an experiment. In this experiment, treats made of fish and biscuit were attached to a string. The treats were blocked from the cat by a transparent screen, so the cat could not get at the treats without using the string to pull a treat to herself. (ref 1). The experiment was to see if the cat could figure out that it needed to pull on the string to bring the treat closer and so demonstrate a reasonably sophisticated understanding of cause and effect.

With a single string cats did ok. But then the researchers sneakily added more than one string to choose from - and only one was attached to the food. The cats were unable to work out which string they were supposed to pull, and tended to pull any string at random. Previous experiments showed that dogs performed much better.

The conclusion Dr Osthaus drew from those experiments is that cats don't understand the function of the string, which meant that they were poor at understanding cause and effect and therefore relatively unintelligent. But with all due respect to the good doctor, is that conclusion warranted?

The thing with dogs is that most canines are eager to please. Their incentive to perform an experiment is partly to be rewarded with food, and partly to get the approval of the human experimenter. The only reason a cat will participate in a food-related experiment is that it is hungry enough to be bothered.

On the other hand, if food is not the principal reason why the cat pulls the string, then it may be that the cat considers the movement of the string itself is entertainment enough. This goes back to the way a cat hunts. A cat will start stalking a prey if something the cat fancies happens to come along, but with most domestic cats the thrill is in the hunt, not in the meal that follows. If the cat does succeed in making a kill that does not necessarily mean that the victim will be eaten. Actually, more often than not the corpse is abandoned, or brought home in case the humans there fancy a snack. (and admittedly the failure of some cats to appreciate that their humans will never recognize the nutritious value of a freshly killed rat does argue either for their stubbornness or a lack of intelligence.) Nevertheless, the fact that only a small percentage of what is killed, is actually eaten by domestic cats means that the thrill of a hunt is more important than the meal at the end of it.

So with the string, it may be that the cat was interested in the movement of the string as mimicking the movement of potential prey. This is more interesting than the prey itself which, being a biscuit, is already 'dead'. Therefore the 'prize' is ignored, just as many a dead mouse is ignored once it offers no more entertainment. For the cat, the movement of the string is the thing, and whichever string it moves, for the cat the result is the same; fun things move around. So why do some cats just stop playing altogether?

Well, cats might understand cause and effect, but just because you offer them cause they will not automatically provide the effect. Call your pets from the garden and the dog comes running. The cat takes a message. And the cat really does take a message. It knows you want her, so, if she wants to she will be along once she has finished what she was doing when you called. So a cat is not going to pull a string because it can. It knows the game, and will play or not play when it is ready.

So, on to the next article.
This was recently published by Dr Shultz and Professor Robin Dunbar her colleague at the Institute of Cognitive and Evolutionary Anthropology (ICEA) at the University of Oxford (ref 2).

The researchers analysed available data on the relative brain and body size of more than 500 species of living and fossilised mammals. They found that the brains of monkeys have grown the most over the millennia, followed by horses, dolphins, camels and dogs. The study also showed that groups of mammals with relatively bigger brains tend to live in stable social groups. The brains of more solitary mammals, such as cats, deer and rhino, grew much more slowly during the same period. Remarks Professor Robin Dunbar: 'For the first time, it has been possible to provide a genuine evolutionary time depth to the study of brain evolution. It is interesting to see that even animals that have contact with humans, like cats, have much smaller brains than dogs and horses because of their lack of sociality.'

Following the publication of this research, the media immediately jumped to conclusion that cats were once again shown to be less intelligent than dogs.

But hold on a moment.
Let's consider another article, this one published in 2009 in the Biological Journal of the Linnean Society (ref 3). The researchers here investigated the skull size – considered as the longest length between the front and back parts of the skull and the volume inside the cats’ respective craniums. Their subjects were big cats - a large sample of tigers, lions, leopards and jaguars. What they found was unexpected. The tiger has a much bigger brain relative to the other three species, which all have similar relative brain sizes.

As the lead author of this research (Dr Nobby Yamaguchi of Oxford University's Wildlife Conservation Research Unit (WildCRU)), explains: 'When we compare the two biggest species, on average the lion has a bigger skull than the tiger based on the greatest length of the skull. However, the tiger has a bigger cranial volume than the lion. It is truly amazing that tiny female Balinese tiger skulls have cranial volumes as large as those of huge male southern African lion skulls.'

Following the recent research from ICEA one would expect that that social species, such as lions, would have larger brains than solitary species, such as tigers. After all they have a more complex social life. But this is clearly not the case.

Anyway, discussions of brain size beg the question of whether a larger brain size or volume means higher intelligence. Is there a direct correlation? Does size really matter here, or is quality more important than quantity?

Perhaps one should look at the number of neurons (the cells mainly responsible for brain function) and the number of synapses (connections) they make. If we just focus on neurons in the cerebral cortex (the thinking part of the brain), we will notice that the dog logs in at 160 million neurons. This is much fewer neurons than an average cat, which has 300 million neurons (almost double the amount) (ref 4). Since the brains of dogs are bigger than cats there is probably a lot of empty space in there. Going purely by brain size means that women are slightly less intelligent than men, and both genders are about seven times dumber than whales, and also have a quarter of an elephant's IQ. Or maybe brain size in animals is about as relevant as the size of a personal computer is to its calculating ability.

So in conclusion, it is not possible to give a definite answer to the question whether dogs or cats are more intelligent. There are things which the dogs do better than cats and vice-versa. But until we know what each species is thinking as it goes through an experiment, we have no idea of how well the animal is doing that thinking. We might also note that both cats and dogs have found a way to live free in human houses, often with regular food, rest breaks and a good medical plan. To an objective observer this might make both species more intelligent than the humans who perform these services for them.

And for those people who think that domestic cats are not intelligent enough to learn tricks we will leave you with this video from a Russian circus:



  1. Whitt, E., Douglas, M., Osthaus, B. & Hocking, I. Domestic cats (Felis catus) do not show causal understanding in a string-pulling task. Animal Cognition (2009) 12(5), pp.739.
  2. Susanne Shultz and Robin Dunbar. Encephalization is not a universal macroevolutionary phenomenon in mammals but is associated with sociality. PNAS (2010) 107(50) pp.21582-21586
  3. Yamaguchi et al. Brain size of the lion (Panthera leo) and the tiger (P. tigris): implications for intrageneric phylogeny, intraspecific differences and the effects of captivity. Biological Journal of the Linnean Society (2009) 98(1)pp.85-93
  4. List of animals by number of neurons.
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