The Smartest Animals On The Planet

Measuring animal intelligence is problematic. Brain size, vocabulary, tool use, and social learning are common metrics of animal smarts, although it's difficult to compare between species since most intelligence tests or tasks are designed for a specific animals.

"There's not a ranking of animals that puts one animal as smarter than the other," according to Virginia Morell, author of "Animal Wise."

Animals evolve certain kinds of cognitive abilities to deal with pressures in their natural habitat, said Morell. Chimpanzees, for example, can make tools to hunt. Dogs may not use tools, but it doesn't make them less bright. They're just good at other things.

We also tend to underestimate the brainpower of animals by relying too much on intelligence tests based around what humans are capable of. Right now, most people perceive speech as the main thing that separates humans from other animals, "but it's clear that parrots, dolphins, whales, and elephants have many more parts of language than we've recognized," Morell said to Business Insider.

And there are a lot of unknowns. We understand that comparing brain to body size is one way to measure intelligence, but "scientists aren't sure if that means you need a large brain, or just the ability to pack in a lot of neurons," said Morell.

The good news is "we're getting a better idea of how animals think and experience the world," Morrell said. "They aren't just roaming around feeling nothing. We know they do things with intentions, they have places to go, things to do, and they can never relax. Our sense of superiority is highly misplaced."

Barring a definitive ranking, here are the animals that have surprised humans with their thinking abilities.

Chimpanzees are better at humans in some memory tasks

Our closest living relative is, unsurprisingly, not a fool. Primatologist Fras de Waal, of Emory University, crowned a young chimpanzee, named Ayumu, as number one on his list of "10 Animal Noble Prize for Overall Smartness" for outperforming humans at a memory task. Ayumu remembered the correct order of a series of numbers when they appeared at random for just 210 milliseconds on a touchscreen monitor - crushing human kids in the same task.

Chimpanzees are also known for their tool-making skills (De Waal notes that chimps have been seen fashioning spears out of sticks) and for learning how to communicate using sign language.

Goats recently amazed scientists by quickly solving a "mechanical puzzle" that caused a box to open, delivering a piece of fruit.

The goats also remembered the task after 10, suggesting they have "excellent long-term memory," co-author Dr Elodie Briefer, at ETH Zurich, said in a statement.

Elephants can work together

Elephants are large animals with big brains. They are considered smart for several reasons: they break off sticks with their trunks, have incredible memories, and seem to be capable of empathy.

Elephants also work together to solve puzzles, according to researcher Joshua Plotnik from the University of Cambridge in England. In one experiment, two elephants had to drag ropes attached on either side to a table holding two food bowls. This required cooperation because only one elephant pulling wasn't enough.

Parrots can reproduce sounds of the human language

We all know parrots can reproduce sounds of the English language (or other languages). But some even have an understanding of the meaning of these words.

The most impressive example of this ability is Alex, an African Grey parrot, who knew colors and shapes and learned more than 100 English words. He was trained by Irene Pepperberg, a comparative psychologist at Brandeis University and Harvard.

Before Pepperberg's groundbreaking work with Alex, "scientists had little expectation that any bird could learn to communicate with humans," the New York Times wrote in 2007, following Alex's death.

In the video below, you can hear Alex answer different questions about the same objects, which "shows us that he really understands what those questions mean," according to Pepperberg:

Dolphins can recognize themselves in the mirror

If scientists used brain size as metric of "intelligence," then dolphins would be "second in intelligence to modern humans," Lori Marino, a senior lecturer in neuroscience and behavioral biology who studies marine mammals - including dolphins - at Emory University once told Discovery News.

In 2012, Marino told the Associated Press: "These mammals recognize themselves in the mirror and have a sense of social identity. They not only know who they are, but they also have a sense of who, where and what their groups are. They interact and comprehend the health and feelings of other dolphins so fast it as if they are online with each other."

Morell also said that dolphins can "imitate human postures" a type of mimicry that is "cognitively demanding."

Previous studies have shown that crows (along with rooks and jays) are at the top of the bird I.Q. scale. A particularly clever species of crow, native to the Pacific island of New Caledonia, recently demonstrated the ability to understand or learn cause and effect relationships similar to the ability of 5- to 7-year-olds.

Morell notes in an article for National Geographic: "New Caledonian crows are among the most skilled of tool-making and tool-using birds, forming probes and hooks from sticks and leaf stems to poke into the crowns of the palm trees."

A 2007 study found that western scrub-jays plan for the future by storing food that they think will be limited in the future. Anticipating future needs - those that are not motivated by instinct (like building a nest) or immediate needs (like hunger) - is a complex skill that was previously considered to be uniquely human, according to researchers from the University of Cambridge.

"In many ways dogs may be more human-like than any other species, even non-human primates," researchers wrote in a 2008 dog intelligence study published in the Journal of the Experimental Analysis of Behavior.

In a separate study, Brian Hare, an expert in canine cognition, showed that dogs can follow and respond to human gestures, like pointing and eye movements, without training. This so-called "theory of mind" ability "is so important to our species," writes Slate's David Grimm, "that without it, we would have trouble learning and interacting with the world around us."

One the smartest dogs in the world (or at least with the most impressive vocabulary) is a border collie named Rico. Rico knows the name to more than 200 items - he can retrieve the object from a jumble of stuff after hearing the name only once. (Rico also took third prize in De Waal's "Animal Noble Prizes")

Another dog, Chaser, knows more than 1,000 objects and can understand English grammar. She isn't the first animal to have a basic understanding of grammar. Studies published in the journal Cognition in 1984 indicated that dolphins can also grasp elements of grammar. Apes have as well, including Kanzi the bonobo.

Here's a video of Rico being amazing:

Cats are independent

Cats are more difficult to study than dogs, as these fuzzballs (being typical cats) don't really like to participate in experiments. But this lack of interest in and of itself may be a sign of their smarts.

Writing for the Huffington Post, medical sociologist Joan Liebmann-Smith said: "Unlike dogs, which are pack animals, cats can fend for themselves; they don't need to depend on others for hunting food or even grooming. And the experts claim that cats' curiosity, tempered by their cautious behavior, are also evidence of their high intelligence."

Steve Smeyers/YouTubeA cat has figured out how to open a door.