⚠️This fact has been debunked
The claim of 300 billion neurons is incorrect by three orders of magnitude. The octopus has approximately 500 million neurons total, not 300 billion. The confusion may stem from the fact that about 300-350 million neurons are in the arms (but that's millions, not billions). For comparison, humans have about 100 billion neurons - the claim would make octopuses have 3x more neurons than humans, which is false.
On average, there's 300 billion neurons in the octopus brain.
The Octopus Brain Myth: 300 Billion Neurons Debunked
You've probably heard the mind-blowing claim that octopuses have 300 billion neurons in their brains. It sounds incredible—three times more than humans! There's just one problem: it's completely false.
The actual number? About 500 million neurons total. That's 600 times smaller than the myth suggests. For context, humans have roughly 100 billion neurons, and dogs have around 500 million—putting octopuses in the same neurological ballpark as your golden retriever, not a sci-fi superintelligence.
Where Did the 300 Number Come From?
The confusion likely stems from a real fact: octopuses do have approximately 300-350 million neurons in their eight arms. Someone probably saw "300" and "neurons" in the same sentence and accidentally upgraded millions to billions. It's an easy mistake with a 1,000x difference in scale.
But here's what makes octopuses genuinely remarkable—it's not the quantity of neurons, it's the distribution.
Two-Thirds of Their Brain Is in Their Arms
Unlike humans, whose neurons are heavily concentrated in the skull, octopuses spread the computing power around. Here's the breakdown:
- Arms: 300-350 million neurons (about 60-70% of the total)
- Optic lobes: 120-180 million neurons
- Central brain: Only 45-50 million neurons
That's right—an octopus's brain is actually the smallest part of its nervous system. The arms do most of the thinking.
Why Arms That Think
This decentralized setup means each arm operates semi-independently. When an octopus arm touches something, the neurons in that arm can process sensory information and initiate movement without waiting for brain approval. It's like having eight additional mini-brains, each handling its own tasks.
Researchers have observed severed octopus arms continuing to react to stimuli and even attempting to bring food to where the mouth used to be. Creepy? Absolutely. But it proves the arms aren't just remote-controlled appendages—they're intelligent in their own right.
The central brain and arms are connected by only about 30,000 nerve fibers, which is remarkably few. This suggests the brain acts more like a coordinator than a micromanager, trusting each arm to handle local decision-making.
Still Impressive, Just Accurate
So no, octopuses don't have 300 billion neurons. But 500 million neurons distributed across a boneless body with eight semi-autonomous limbs? That's plenty strange and wonderful on its own. Sometimes the truth doesn't need exaggeration—it just needs better PR.