Which Is Smarter, Dogs or Cats?

Cat and Dog。圖片來源：Pingz Man，採用 CC BY 2.0 授權。

Before attempting to answer whether dogs are smarter than cats, we first need to clarify what “smart” actually means. In everyday discussion, people often equate intelligence with something like an IQ score. For humans, IQ can be assessed through standardized tests. However, animals such as dogs and cats cannot take these kinds of tests, so scientists must rely on other methods when trying to estimate animal intelligence.

For a long time, one of the most intuitive approaches was simply to look at brain size. The reasoning seemed straightforward: animals with larger brains should be more intelligent. Yet this idea quickly ran into problems. If brain size alone determined intelligence, then the smartest animals on Earth should be enormous species such as whales. The blue whale, for instance, possesses a massive brain, yet few people would argue that it surpasses humans or primates in cognitive ability. One explanation is that larger animals require more neural tissue simply to control their larger bodies. Coordinating muscles, processing sensory input, and maintaining physiological regulation all demand additional neural resources.

Because of this limitation, researchers turned to a second measure: the ratio between brain size and body size. Animals with relatively large brains compared with their body mass were thought to possess higher intelligence. This concept appeared promising for a while, but further evidence revealed that it also failed to provide a reliable measure of cognitive ability.

More recent research has shifted attention to a different factor: the number of neurons in the cerebral cortex. The cerebral cortex is the region of the brain responsible for integrating information, planning behavior, and carrying out complex forms of thought. Neurons themselves serve as the fundamental units that process and transmit information. Importantly, brain size does not necessarily correspond directly to neuron number. A larger brain does not always contain proportionally more neurons; sometimes it simply contains larger neurons or more supporting cells. Consequently, the number of cortical neurons is now considered a more informative indicator of potential cognitive capacity.

This perspective helps explain why brain size alone can be misleading. Even among humans, variations in brain structure illustrate this point. For example, Albert Einstein's brain did not stand out because of its overall size but because of features such as unusually high neuronal density in certain regions. In other words, the organization and number of neurons matter more than raw volume.

With this framework in mind, the question of whether dogs or cats are more intelligent becomes easier to approach. A study published in 2017 examined the brains of several carnivoran species to determine how many neurons were present in their cerebral cortex. The researchers analyzed eight species: ferrets, banded mongooses, raccoons, domestic cats, domestic dogs, striped hyenas, lions, and brown bears. By examining the cellular composition of the cerebral cortex, the study sought to determine whether body size, evolutionary relationships, or domestication affected the number of cortical neurons.

The results revealed several interesting patterns. In general, larger animals tended to possess larger cerebral cortices, and cortical mass often correlated with neuron numbers. However, the relationship was not perfectly proportional. As cortical mass increases, neurons themselves also tend to become larger, meaning that neuron numbers do not always rise at the same rate as brain volume.

One particularly surprising finding involved the brown bear. Despite having one of the largest brains among the species examined, its cerebral cortex contained only about as many neurons as that of a domestic cat—approximately 250 million neurons. This result highlights why brain size alone cannot serve as a reliable measure of intelligence. The bear's cortex occupies far more space, yet the number of neurons within that tissue does not increase accordingly. Other components of brain tissue, such as glial cells, also occupy space and contribute to the overall mass of the brain.

The study also examined whether domestication influences neuron numbers. Three of the species included in the analysis—ferrets, domestic cats, and domestic dogs—are domesticated animals. The results suggested that domestication itself does not significantly alter the neuronal composition of the brain. Domesticated species still followed the same general scaling patterns observed in their wild relatives.

Returning specifically to the comparison between cats and dogs, the numbers are quite revealing. A mixed-breed dog weighing about 7.45 kilograms was estimated to possess roughly 429 million neurons in the cerebral cortex. A larger golden retriever weighing around 32 kilograms was estimated to have approximately 623 million cortical neurons. In contrast, the domestic cat's cerebral cortex contained about 250 million neurons.

If one uses cortical neuron number as an indicator of cognitive capacity, dogs would therefore appear to have a theoretical advantage over cats. Their cerebral cortex contains substantially more neurons capable of processing information, which could support more complex behavioral and cognitive abilities.

However, this conclusion should be interpreted with caution. Intelligence is not a single trait that can be measured in the same way across different species. Animals often evolve cognitive abilities tailored to their ecological roles and behavioral strategies. Even if dogs possess more cortical neurons, this does not automatically mean that they outperform cats in every type of problem.

Experimental studies of animal behavior illustrate this point clearly. Dogs and cats can both solve challenging tasks under experimental conditions. Dogs, having undergone thousands of years of domestication alongside humans, tend to be highly responsive to human cues. They often rely on humans for guidance and may look to people for help when confronted with unfamiliar problems.

Cats behave differently. Experiments suggest that cats are capable of understanding human signals and instructions, but they are often less motivated to respond. In many cases, they appear to recognize what a human wants yet choose to ignore it. This difference in behavior can make cats appear less intelligent, even though their cognitive abilities may simply be expressed in a different way.

Furthermore, dogs and cats tend to excel at different types of tasks. Dogs frequently perform well in experiments involving social communication with humans, cooperation, or following gestures. Cats may be better suited to tasks involving independent problem solving or solitary hunting strategies. Their evolutionary history as solitary predators has likely shaped the way their cognition operates.

For these reasons, the question of whether dogs or cats are smarter does not have a simple answer. From a purely theoretical perspective based on cortical neuron numbers, dogs likely possess a higher potential for complex cognitive processing. Yet practical comparisons remain difficult because dogs and cats differ in their motivations, social behaviors, and ecological adaptations.

In the end, intelligence in animals cannot be reduced to a single number. Dogs and cats each represent distinct evolutionary strategies for interacting with the world. Dogs may have an advantage in certain types of cognitive tasks, particularly those involving cooperation with humans. Cats, on the other hand, have evolved a form of intelligence that emphasizes independence and stealth.

Future research comparing the cognitive abilities of cats and dogs in controlled experiments may provide clearer insights into their relative strengths. Until then, the most reasonable conclusion is that dogs may be theoretically more intelligent according to neuronal counts, but cats and dogs simply think in different ways.

Author: Bai Leng

Reference:

Messeder, D. E., Lambert, kelly., Noctor, S., Pestana, F. M., Leal, M. E. D. C., Bertelsen, M. F., Alagaili, A. N., Mohammad, O. B., Manger, P. R., Houzel, S. H. (2017). Dogs Have the Most Neurons, Though Not the Largest Brain: Trade-Off between Body Mass and Number of Neurons in the Cerebral Cortex of Large Carnivoran Species. Neuroanat.