The Smartest Animals in the World, Ranked by the Evidence

How to rank minds built for different worlds

No animal can sit an IQ test. Human tests are written in human language, timed for human hands and normed on human populations. Comparing a crow with a dolphin on a single number would be meaningless. What scientists can compare is performance on a set of demanding tasks that recur across species.

We ranked on five: recognizing oneself in a mirror; using and, harder still, making tools; learning from others and passing skills down as culture; communicating with symbols or learned signals; and memory and planning. A species ranks high when it shows strength across several of these, in studies that have been replicated or published in leading journals. Breadth beats a single spectacular trick.

Brain size alone does not settle it. Humans top the encephalization quotient, a measure of brain size relative to body size, at 7.4 to 7.8; bottlenose dolphins follow at 5.26, then chimpanzees at 2.2 to 2.5 and ravens at 2.49. But the measure was built for mammals and fits birds poorly, and researchers now see forebrain neuron counts as a better predictor of intelligence. The idea that intelligence comes in several kinds, familiar from Howard Gardner's multiple intelligences, applies across species too.

The ranking at a glance

The top three are the consensus of the field. Below them, reasonable researchers would reorder the list: a corvid specialist might rank ravens above elephants, and octopuses are hard to place because their intelligence evolved on a separate branch of the animal tree.

1. Great apes: the benchmark

The modern science of animal self-awareness began with chimpanzees. In 1970 psychologist Gordon Gallup marked anesthetized chimpanzees with red dye in spots they could see only in a mirror. Once they woke, they touched the marked spots far more often with a mirror than without one. They knew the face in the glass was their own. Bonobos and orangutans have since passed; results for gorillas are mixed.

Tool making came first. In 1960 at Gombe, in what is now Tanzania, Jane Goodall watched chimpanzees strip leaves from twigs and poke them into termite mounds to fish out insects. Louis Leakey's response is famous: science would have to "redefine man, redefine tool, or accept chimpanzees as human."

The bonobo Kanzi, who died on March 18, 2025, at 44, used more than 348 lexigram symbols. Primatologist Sue Savage-Rumbaugh reported that he understood about 3,000 spoken English words; in one test of spoken instructions he responded correctly 74 percent of the time, against 65 percent for a human toddler. At Kyoto University's Primate Research Institute, a young chimpanzee named Ayumu beat university students at a short-term memory task: recalling, in order, numerals shown briefly on a touchscreen.

Orangutans build a fresh nest every night and, at Suaq Balimbing in Sumatra, carry tool kits of insect-extraction and seed-extraction sticks. In 2022 researchers watched a male called Rakus chew the leaves of a medicinal vine and apply the paste to a wound on his face. It healed within weeks.

2. Bottlenose dolphins

In 2001 Diana Reiss and Lori Marino reported in the Proceedings of the National Academy of Sciences that bottlenose dolphins recognized themselves in mirrors. Marked dolphins swam to the mirror faster, circled their heads and inspected the marked spots, behavior that makes sense only if the animal knows whose body it is seeing.

Each dolphin develops a signature whistle that works like a name, and dolphins have recognized the whistles of former companions after 20 years apart. In Shark Bay, Western Australia, some dolphins wear marine sponges on their snouts to protect them while foraging on the seabed, a technique passed from mothers to offspring. That is culture in the strict sense: a learned skill, carried by some lineages and absent in others.

3. Elephants

In 2006 Joshua Plotnik, Frans de Waal and Diana Reiss tested three Asian elephants at the Bronx Zoo with an elephant-sized mirror. One, named Happy, repeatedly touched a painted X on her head with her trunk, a mark visible only in the reflection. The other two did not, which is why the result is strong but not universal.

A 2011 study showed that elephants coordinate with a partner, each pulling one end of a rope at the same moment to win a reward. They modify branches to swat flies and scratch themselves. An elephant brain weighs about 5 kilograms and holds about 257 billion neurons, three times the human count, yet its cerebral cortex has only a third as many neurons as ours. Raw neuron totals, like raw brain size, do not rank minds by themselves; the story of Einstein's brain makes the same point about humans.

4 and 5. Crows, ravens and parrots

In 2002 Alex Kacelnik's group at the University of Oxford reported in Science that a New Caledonian crow named Betty, faced with food in a tube and only a straight wire, bent the wire into a hook. She did it in nine of ten successful retrievals. In a later experiment, six of seven crows used a short stick to fetch a longer stick that could reach the food, a sequence once documented only in primates. Wild New Caledonian crows cut stepped tools from pandanus leaves.

Ravens plan. In 2017 Can Kabadayi and Mathias Osvath reported in Science that ravens chose tools, and tokens they could later trade with humans, for use in the future rather than the moment. A 2020 study found that four-month-old ravens performed about as well as adult chimpanzees and orangutans on a battery of physical and social cognition tests. The magpie mirror result of 2008 is less secure: a larger 2020 replication failed to confirm it.

Parrots bring language into the picture. Irene Pepperberg worked for 30 years with Alex, an African grey who lived from 1976 to 2007. He used more than 100 words, identified 50 objects, seven colors and five shapes, handled quantities up to six and grasped same and different, bigger and smaller. Pepperberg judged some of his abilities comparable to a five-year-old child's.

6. Octopuses: intelligence on a separate branch

An octopus has more than 500 million neurons, about as many as a dog, and two-thirds of them sit in the nerve cords of its arms rather than its brain. Its intelligence evolved independently of ours; the last common ancestor was a simple animal with nothing resembling a complex brain.

The evidence is striking. In 2009 Julian Finn and colleagues reported in Current Biology that veined octopuses carry discarded coconut shells over distance and assemble them into shelters, carrying a tool for later use. In 1992, Graziano Fiorito and Pietro Scotto showed in Science that octopuses learn by watching: observers that saw another octopus choose one of two colored objects consistently chose the same one. Octopuses unscrew jar lids and open latched boxes to reach food.

7 to 10. Pigs, dogs, capuchins and a fish

Pigs. In 2009 Donald Broom and colleagues reported that seven of eight pigs given five hours with a mirror used it to find a bowl of food hidden behind a wall. Pigs have not passed the formal mark test, but they use reflections as information. In a 2021 study in Frontiers in Psychology, pigs learned to steer a joystick with their snouts to hit targets on a screen.

Dogs. Chaser, a border collie trained by psychologist John Pilley, learned the names of 1,022 toys, the largest tested memory of object names in any nonhuman animal. Pilley and Alliston Reid reported in 2011 that she also inferred the names of new toys by exclusion, choosing the unfamiliar object when she heard an unfamiliar word.

Capuchin monkeys. Capuchins crack nuts by placing them on flat stones and striking them with heavier ones, choosing hammer stones by weight for each food. A 2019 study in Nature Ecology & Evolution found that some wild populations have kept this stone-tool culture for at least 3,000 years.

Cleaner wrasse. In 2019 Masanori Kohda and colleagues reported in PLOS Biology that these small reef fish, marked with a colored tag, scraped the spot against surfaces after seeing it in a mirror. The claim is debated, but a 2022 follow-up by the same team strengthened it. If it holds, the mirror test measures something more widespread than anyone assumed in 1970.

What animal minds reveal about intelligence

The ranking carries a lesson for human intelligence. Every species on this list is brilliant at the problems its world posed: a crow at shaping twigs, a dolphin at tracking relationships in open water, an octopus at solving puzzles with limbs that half think for themselves. Intelligence is not one ladder with humans at the top and everything else on lower rungs. It is a set of capacities that evolution builds in different combinations.

Human IQ tests measure one well-defined slice of that set, the reasoning that predicts success in school and many jobs. Our explainer on what counts as a high IQ covers what the human scale captures, and our guide to how IQ tests work explains why no such scale can be applied to a chimpanzee or a crow. For the human side of the rarity question, see how many geniuses there are.

Editorial standard: IQ figures for historical figures are retrospective estimates and are labeled as such; scores for living people appear only when the person disclosed them or a reputable outlet reported them. Corrections: contact the editors.