One easy way to start an argument is to announce that dogs are smarter than cats or vice versa. It seems that everybody has an opinion of our most familiar pets, yet it seems that few people have actual data to base their claim upon. However scientists have recently designed certain techniques and measures that may give us the definitive answer.

Comparing the intelligence of animals of different species is difficult although there are certain tests and problem sets that have proved to be useful. Making the tests equivalent, however, for say a dolphin that lives in the water and a horse that lives on the land is obviously complicated and may prove to be virtually impossible. In the case of dogs versus cats we also have a problem, since each are specialized to do different things. Dogs are designed to be more efficient runners while cats have better ability at manipulating things with their paws. Thus a test that involved pulling strings or operating levers would tend to favor a cat, while a test involving moving from place to place, where speed is a measure of performance, would favor a dog. Charles Darwin claimed, "Intelligence is based on how efficient a species became at doing the things they need to survive," and one might argue that by this definition all species that stay healthy, remain numerous and avoid extinction are equally intelligent.

Because of such measurement problems, psychologists and biologists have looked for a technique for assessing intelligence that doesn't require specific tests or even the cooperation of the animals involved. It starts with the argument that a bigger brain must be better since it allows more memory storage and faster processing simply because it would have more neurons and connections. For example, a person with a brain size of 1500 cm3 would have an average of 600 million more cortical neurons than a person with a brain size of 1400 cm3. So the first guess might be that animals that have bigger brains must be smarter.

As a first comparison we see that humans have larger brains (averaging 1,400 grams) than dogs (averaging 72 grams) with the rhesus monkey falling in-between (at 97 grams), and this makes sense in terms of our general impression of the relative intelligence of these species. However if we use brain weight alone we would be forced to conclude that the elephant with its 6,000 gram brain is brighter than man, and that the super geniuses of the earth are whales-for instance the sperm whale has a brain that averages 7,800 grams. The problem is that larger animals have larger brains. They need to in order to control the movements of their larger masses of muscles. They also need a larger brain to process sensory information-for example every added square centimeter of skin surface will need more cortical neurons to process the sense of touch, heat, cold and pain from that region of the body.

In the late 1970's the psychologist Harry J. Jerison developed an alternative measure that he called the Encephalization Quotient or EQ. It is a mathematically sophisticated comparison of the actual brain weight of an animal compared to the expected brain mass for that animal's body size. This compensates for the fact that bigger animals tend to have bigger brains and basically shifts the question to one of whether the animal has a larger or smaller brain size than what we would expect for an animal with its body mass.

Based on the encephalization quotient, the brightest animals on the planet are humans, followed great apes, porpoises, and elephants. The dog is close behind elephants in its EQ. Descending down the list we find cats lower than dogs, followed by horses, sheep, mice, rats and rabbits. As a general rule, animals that hunt for a living (like canines) are smarter than strict vegetarians (you don't need much intelligence to outsmart a leaf of lettuce).

Another factor is that appears to be very important is how social the animals are. Animals that live in social groups are always smarter and have large EQ's than solitary animals. This is because social animals must engage in problem solving every time they interact with another animal in the group. This involves reasoning like "If I do this, then he'll do that, so I can do that other thing." This means that the social chimpanzees are smarter than the solitary orangutan. This piece of data is also consistent with the fact that dogs are more intelligent than cats, since dogs are much more social animals than cats, and interaction in packs often involves complex rituals and behaviors.

However a real surprise occurs in some recent data provided by Suzanne Shultz and Robin Dunbar at Oxford University. They wondered about whether there had been evolutionary changes in the Encephalization Index. For example, when we domesticate animals, especially a companion animal like a dog, we are placing new demands upon it. Some of these demands are social in nature, such as understanding human communication gestures and words. Dogs are subjected to more of this pressure than are cats. Thus it might be expected that dogs would show a greater rise in their EQ than cats. This was verified by the Oxford researchers using 511 different samples ranging from extinct species only available as fossils, up through current living examples. Thus it appears that based on their EQ dogs are becoming progressively more intelligent over time while cats have remained at much the same level of mental ability that they had when we first domesticated them. This means that not only are dogs smarter than cats, but the gap between the species is increasing over time.

At the risk of starting another argument, these data may explain why we never hear about such things as a "seeing eye cat," "police cat" or "search and rescue cat."

Stanley Coren is the author of many books including: Born to Bark, The Modern Dog, Why Do Dogs Have Wet Noses? The Pawprints of History, How Dogs Think, How To Speak Dog, Why We Love the Dogs We Do, What Do Dogs Know? The Intelligence of Dogs, Why Does My Dog Act That Way? Understanding Dogs for Dummies, Sleep Thieves, The Left-hander Syndrome

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.

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