Measuring intelligence between animals and people is a difficult task. For animals, the distinction between different levels of cognitive ability becomes even more difficult as other factors are included which affect how you determine how "smart" an animal is. These factors include things like brain size, vocabulary, tool use, and social learning. But it's still difficult to compare because what might be considered "smart" for one animal may also be considered "dumb" for an animal of a different species. As a result, we tend to compare animals to ourselves, and the animals who have the thinking ability most similar to humans are considered to be the smartest.
1. Chimpanzees
It should come as no surprise that our closest relative in the animal kingdom is also the smartest. In some cases, these animals have even been shown to outperform humans in certain tasks! For instance, a young chimpanzee named Ayumu participated in a memory game with university students where each participant had to remember a sequence of numbers. Ayumu succeeded in beating every single student giving evidence that chimps might actually have better working memory than humans! Additionally, chimps have been recorded making tools (including spears) out of sticks and have even been taught to communicate using sign language.
2. Goats
Most people wouldn't guess it, but goats are actually considered to be very intelligent animals who are also curious about the world around them. In fact, when presented with something that a goat hasn't seen before, rather than try and run away from it, a goat will actually go over to investigate. This was best exemplified during a mechanical puzzle test in which a goat had to figure out how to open a mechanical box in order to get a piece of fruit. To the amazement of the scientist monitoring the test, the goat actually figured it out very quickly!
3. Elephants
Even though they don't look like us (like, at all) elephants actually have many traits similar to human beings. For one, elephants have been known to use tools, with an ability to break branches using their large and powerful trunks and use them to accomplish tasks. Additionally the phrase "memory like an elephant" isn't just a thing that people say - it's actually been proven that elephants have incredible memories and are even capable of emotions like empathy. But most incredibly, elephants have been shown to be able to work as a team, with the University of Cambridge giving two elephants tasks that could only be accomplished by them both working together, something the elephants succeeded at.
4. Parrots
It's well known that parrots can mimic the sounds of people and other animals, but many have wondered if these animals know what they're saying of if they're just repeating what they hear. Well, it turns out that these animals might actually be able to communicate with the words they know. The best example would be Alex the African Grey parrot, who was able to distinguish between various shapes and colors. Additionally, some parrots have been known to make the sound of a doorbell or cell phone ringing since they know it will bring their owners running into the room.
5. Dolphins
Next to humans, dolphins have the largest brains in proportion to their size. As a result, they're able to do some pretty impressive things like demonstrating self-awareness, solve problems as individuals and in a team setting, and demonstrate complicated emotions like empathy, grief, joy, and can even teach one other skills that they themselves have been taught. With all that, these animals are almost starting to sound like humans with fins! Their most cognitively impressive ability is how they're able to mimic human behavior which, according to researchers, requires a significant amount of brainpower for any animal to do.
6. New Caledonian Crows
Crows are considered to be at the top fo the I.Q. list for birds, with higher cognitive abilities than even parrots and cockatoos. In fact, crows have an understanding of cause and effect that is similar in ability to 5 to 7-year-old humans! They are also quite skilled with tools, many of them actually building hooks and probes from sticks and other plants in order to poke into the top of palm trees. When offered a reward, such as food, crows can even solve semi-complicated puzzles such as a test requiring a crow to raise the water level of a tube to match the second tube in order to get some food.
7. Scrub Jays
Scrub jays also have a surprisingly large brain-to-body ration, with one that actually rivals that of the chimpanzee. Researchers found that these birds are actually smart enough to do complex tasks like planning for the future. This was discovered in a 2007 study in which Scrub jays would store food if they believed that food would be limited in the future. This means that these birds aren't just motivated by basic instinct, but rather have a skill that was once believed to have been unique only to human beings.
8. Dogs
Dogs have been able to accomplish what scientists call a "theory of mind" ability. Essentially this means that dogs understand that others have emotions, desires, or motivations which may be very different from their own. Dogs show this quite often, particularly with their ability to understand subtle human behaviors, such as following hand gestures and even eye movement. Additionally, dogs can be trained to understand human language, with one dog, Rico, having been taught the names of more than 200 items.
9. Cats
When it comes to brain neurons between cats and dogs, cats are definitely the winner. These tiny balls of fluff and fangs have 300 million neurons compared to dogs who have only 160 million. This means that cats also have a much larger cerebral cortex which governs abilities like problem-solving, short term and long term memory, and rational thought. Cats are also very curious creatures, which attests to their high intelligence and cognitive ability. Although, in all honesty, scientists find it difficult to study feline intelligence because they are usually unwilling to participate in experiments.