The Average IQ of a Gorilla: How Smart Are Gorillas?

Why "Gorilla IQ" Is a Category Error

Putting a number like "gorilla IQ = 80" next to a human IQ of 80 quietly suggests the two mean the same thing. They do not.

A human IQ score is only meaningful because it compares one person against a large, carefully sampled human population, with a mean fixed at 100 and a standard deviation of 15. There is no such reference population for gorillas, no bank of gorilla-appropriate questions, and no way to separate raw ability from the fact that the animal was raised by humans and coached by a familiar handler. When Koko was tested, critics pointed out that scores were probably depressed by test items that made no sense to a gorilla (naming which of two objects you would run from in the rain, for instance, where a gorilla might sensibly pick the tree it would shelter under rather than the "house" the test wanted).

So a gorilla scoring 80 on a human infant scale is not "as smart as a below-average human." It is a gorilla being asked human questions and doing surprisingly well anyway, on a test that was never designed to capture what a gorilla is good at.

Koko's Story and the 70-95 Caveat

Koko, born at the San Francisco Zoo on July 4, 1971, is the reason most people ever wondered about gorilla IQ. Psychologist Francine "Penny" Patterson raised her from infancy and taught her a modified form of American Sign Language. Over nearly five decades, the Gorilla Foundation reported that Koko learned more than 1,000 signs and understood roughly 2,000 words of spoken English. She died in 2018 at age 46.

The IQ figures come from the early years. Between 1972 and 1977, Koko was given adapted versions of human infant intelligence tests, including items based on the Stanford-Binet scale, and she scored in the 70 to 95 range, averaging about 80. Those are the numbers that echo around the internet today.

Two honest caveats belong right next to that number:

1. The tests were non-standard and contested. They were human infant tests adapted for a gorilla, scored by her own caretakers, and never independently replicated under controlled conditions. Skeptics raised the "Clever Hans" problem, the risk that an animal responds to subtle, unconscious cues from a familiar human rather than solving the task itself.
2. The 1,000-signs figure is the foundation's own count. The broad scientific consensus is narrower than the headlines: Koko clearly used many signs and understood a great deal, but she did not demonstrate the grammar and syntax that linguists treat as the defining feature of true human language.

None of this makes Koko less remarkable. It just means her IQ number is a curiosity, not a measurement you can stack against a human's.

The Real Evidence That Gorillas Are Smart

Strip away the IQ framing and the case for gorilla intelligence is strong and comes from peer-reviewed field science, not one captive animal.

Tool use in the wild. In 2005, researchers from the Wildlife Conservation Society published the first documented cases of wild gorillas using tools. At Mbeli Bai, a swampy clearing in northern Congo, an adult female nicknamed Leah used a branch as a walking stick to test the depth of a pool before wading in. A second female used a detached shrub trunk both as a stabilizer while feeding and as a makeshift bridge across deep swamp. That is problem-solving with improvised objects, in the wild, with no human teaching it.

Self-awareness. The mirror test, long treated as the gold standard for self-recognition, gave gorillas mixed results for years, which some read as a cognitive gap. More recent work, including 2025 studies, argues the mirror test simply does not suit gorillas, who tend to avoid direct eye contact. On body-awareness tasks, gorillas performed just as well as chimpanzees, quickly understanding that their own body was blocking something and adjusting accordingly.

Social intelligence. Gorillas live in stable family groups, form long-term bonds, and show behavior many observers read as grief. Patterson reported that Koko mourned when her pet kitten, All Ball, was killed by a car, producing signs read as sad and cry. Anecdotal, yes, but consistent with the rich emotional and social lives documented across great apes.

The Honest Bottom Line

Gorillas do not have an IQ in any meaningful sense, and the "70 to 95" figure comes from one gorilla, on contested human tests, decades ago. But by the measures scientists actually use, tool use, self-awareness, social cognition, and symbolic communication, gorillas are among the most intelligent animals on Earth. The right conclusion is not "a gorilla is about as smart as a slow human." It is that intelligence comes in shapes our own tests were never built to see.

Curious how the human version of this test actually works, the one where 100 really does mean average? You can try a properly human-normed IQ test yourself.

Frequently Asked Questions

Q: What is the average IQ of a gorilla?

A: There is no true average IQ of a gorilla, because IQ tests are standardized on humans. The only widely cited figure comes from Koko, who reportedly scored between 70 and 95 (averaging around 80) on adapted human infant tests in the 1970s. That result is non-standard and scientifically contested, so it should not be treated as a real IQ.

Q: How smart are gorillas compared to humans?

A: Gorillas are highly intelligent but not comparable to humans on a single scale. They use tools, show self-awareness, live in complex social groups, and can learn symbolic communication. They do not match human abstract reasoning or grammatical language, but "smarter or dumber" is the wrong question, since their intelligence is adapted to a different life.

Q: Did Koko the gorilla really have an IQ?

A: Koko was given adapted human infant IQ tests and scored roughly 70 to 95, but experts dispute the result. The tests were not standardized for gorillas, were scored by her caretakers, and were never independently replicated. Many researchers see the score as an interesting anecdote rather than a valid measurement.

Q: Are gorillas smarter than chimpanzees?

A: Not clearly, and it depends on the task. Chimpanzees have traditionally outperformed gorillas on some lab tests, but 2025 research found gorillas matched chimpanzees on body self-awareness tasks. Both are great apes with sophisticated cognition, and simple rankings between them are unreliable.

References

• Breuer, T., Ndoundou-Hockemba, M., & Fishlock, V. (2005). First Observation of Tool Use in Wild Gorillas. PLOS Biology, 3(11), e380.
• Patterson, F., & Gordon, W. The Case for the Personhood of Gorillas. The Gorilla Foundation.
• Anderson, J. R., & Gallup, G. G. (2022). Mirror self-recognition in gorillas: a review and evaluation of mark test replications and variants. Animal Cognition.
• Gorillas match chimpanzees in self-awareness study (2025). Phys.org / Utrecht University.

Last updated: July 13, 2026