IQ of a Gorilla: What Koko's Tests Really Showed

6 min read · IQ Tester

The most quoted IQ of a gorilla comes from Koko, a western lowland gorilla whose trainer reported scores between roughly 70 and 95 on intelligence tests designed for young children. That's the only real source behind the "gorilla IQ" numbers online, and it comes with big caveats: the tests were made for human kids, and the scoring relied on the people who raised her.

So there's no true average IQ of a gorilla. There's one famous gorilla, one set of reported scores, and a long argument about what they mean.

If you came here wondering how your own reasoning stacks up, that's a question you can actually answer, and IQ Tester shows you which of your skills is weakest: Find my weak spots.

What is the IQ of a gorilla?

IQ tests work by comparing you to a huge group of people your age who took the same test. The middle of that group is set to 100. A gorilla isn't part of that comparison group, so "the IQ of a silverback gorilla" isn't something anyone has properly measured.

What we have instead:

• Koko's reported scores (more on those below).
• Field and zoo studies of gorilla problem solving, memory and tool use.
• Comparisons with chimps, orangutans and bonobos on the same tasks.

Together they say gorillas are clearly smart. They just don't say "gorillas have an IQ of X."

Koko's IQ scores explained

Koko was born in 1971 at the San Francisco Zoo and raised by psychologist Francine "Penny" Patterson, who taught her a version of American Sign Language. Koko died in 2018.

Where the 70 to 95 range comes from

Patterson reported that Koko scored somewhere between about 70 and 95 on infant and child intelligence tests over the years. On the human scale, that range runs from below average to just under average.

Here's the honest context:

• The tests were for human kids. Some items depend on human-style pointing, language or objects that a gorilla wouldn't care about.
• Scoring was done by her own team. That's not shady by itself, but it means no independent check.
• "Child IQ" isn't "adult IQ." A score on an infant test compares her to babies and toddlers, not to grown adults.

Koko and sign language

Koko was said to use around 1,000 signs and understand many more spoken English words. Some researchers were impressed. Others, especially after the Nim Chimpsky project with a chimp, argued that apes mostly produce signs that get rewards and that humans over-read the meaning.

So when you see "IQ of gorilla Koko: 95" on a TikTok slideshow, read it as "a reported top score on a kids' test, interpreted by her trainer," not as a lab-certified fact.

Silverback vs other apes

What is a silverback?

A silverback is an adult male gorilla, usually over about 12 years old, named for the silver-gray hair that grows across his back. He leads a group, protects it and settles fights.

Is a silverback gorilla smarter?

Not necessarily. Being a silverback is about age, size and social role, not test scores. Leading a group does take social skill, like reading moods and keeping peace, but nobody has measured "the IQ of a silverback gorilla" against females or younger males.

The smartest gorilla ever?

Koko is the most famous, so she usually gets called the smartest. Another gorilla often mentioned is Leah, a wild gorilla in the Republic of Congo who was photographed in 2005 using a branch to test how deep a pool of water was before wading in. That was one of the first records of tool use by a wild gorilla.

Gorilla vs chimpanzee intelligence

People love asking which ape is smartest. Here's a rough, fair comparison:

Chimps usually look "smarter" in tool-use studies, partly because they live in environments where tools pay off more. Gorillas eat a lot of leafy plants that don't need cracking open. Being less flashy with tools doesn't mean less brainpower.

Why ape IQ scores are controversial

Here's why scientists side-eye any "average IQ of a gorilla in the world" claim:

1. Wrong test, wrong species. Human IQ tests assume human eyes, hands, motivation and language.
2. Tiny samples. One or two famous apes can't represent all gorillas.
3. The trainer effect. People who love an animal can unconsciously read meaning into its behavior.
4. Reward vs understanding. An ape might give the "right" sign to get a treat without understanding it the way a kid would.

What about "iq gorilla Indonesia"?

Quick myth-buster: there are no wild gorillas in Indonesia. Wild gorillas live in central Africa. Indonesia is home to orangutans, on Sumatra and Borneo, which are also great apes and also very smart. If you saw a viral "Indonesian gorilla" clip, it was likely an orangutan, or a zoo animal.

For a very different take on animal smarts, our IQ of a shark post shows how even animals without a big ape brain can learn in surprising ways.

How human IQ tests are built

To understand why gorilla IQ is messy, it helps to know how the human version works.

1. Questions get written across types like patterns, numbers, words and logic.
2. Lots of people take them, so test makers know how hard each question really is.
3. Scores get converted to a scale where the average is 100 and the standard deviation is 15. Roughly two-thirds of people land between 85 and 115.
4. The final number tells you where you sit compared to that big group.

Step 2 is the step that's impossible for gorillas. Without a big group of comparable test-takers, there's no fair "average."

Doing step 2 for yourself is basically impossible. You can't line up thousands of people and compare. IQ Tester draws 20 untimed questions from a bank across four reasoning types, weights harder ones more, and converts your result to that mean-100 scale, so you skip the guesswork. Find my weak spots

So, what's the final answer on the IQ of a gorilla?

There isn't a reliable one. Koko's reported 70 to 95 is a fun fact with heavy caveats. The better summary: gorillas are thoughtful, social, sometimes tool-using great apes, and IQ is just the wrong ruler for them. If you want a ranking of the other end of the animal spectrum, check out the dumbest animal in the world.

Get a real score on a real test

Koko's numbers came from tests that weren't built for her. Yours can come from one that is. IQ Tester gives you 20 untimed questions, then shows your band and three of your four category strengths for free. If you want the exact score on a 58 to 142 scale, every answer explained and a certificate, that's an optional one-time $7.99 unlock.

Find my weak spots

FAQ

What is the average IQ of a gorilla?

There's no measured average. The only widely quoted figures come from Koko, who reportedly scored about 70 to 95 on intelligence tests made for young children. Those tests weren't built for gorillas, so treat the numbers as a curiosity.

What was Koko the gorilla's IQ?

Her trainer, Penny Patterson, reported scores between roughly 70 and 95 across several child intelligence tests. Critics point out that the scoring was done by her own team and the tests were designed for human kids.

How does the IQ of a gorilla compare to humans?

You can't compare them fairly, because IQ is defined by comparing humans to other humans. Gorillas are clearly intelligent, with good memory, social skills and some tool use, but they don't fit on the human IQ scale.

Are gorillas smarter than chimpanzees?

Chimps use tools more often in the wild and tend to stand out in tool-use studies. Gorillas are less flashy but still smart. Most researchers avoid ranking them, because each species is good at what its life demands.

Who was the smartest gorilla?

Koko is the most famous, thanks to her sign language. Leah, a wild gorilla photographed using a stick to check water depth in 2005, is also often mentioned for showing tool use in the wild.