Likely between 35 and 40, but this is not exactly a fair question—after all, IQ tests are designed for humans! So, how do we know? We can estimate an average IQ based on brain size and cognitive abilities. That’s how we know a smarter chimpanzee’s IQ would likely fall in that range.
To come to this human IQ range for another species, we can get creative and use the Encephalization Quotient (EQ), which measures brain size relative to body size. Humans have an average IQ of 100 and an EQ of about 7.6. Chimpanzees, our clever cousins, have an EQ of around 2.35. If we translate that into human-style IQ terms, it suggests an IQ of about 35. This doesn’t mean they’d actually score 35 on a human IQ test, they wouldn’t. The EQ translation system gives an average estimate for a specific species. It gives us a fun way to think about their intelligence relative to ours. The big difference in abilities and the reason for a 35 to 4o IQ range? Chimpanzees don’t reason abstractly or ask simple questions like “What is that?” or “Where are we going?” A human with an IQ that low would be the same. Below about 55, spontaneous question-asking becomes increasingly rare.
Here’s a fun tidbit: After humans, the smartest animal is likely dolphins. They have an EQ ranging from 4.0 to 5.3. If we use our EQ-to-IQ translation, that puts them in the IQ range of 53 to 69. They’re very different from us, and while we’re still figuring out how to communicate with them, dolphins have also never asked a question. So far, asking questions seems to be a human-only trait.