How Many Brains Does an Octopus Have?

Octopuses have nine brains. They have one central brain (with overall control) wrapped around the esophagus. There are eight additional mini-brains in each of their eight arms. The mini-brains control the arms semi-independently even after the arms detach.

Octopuses are incredibly smart. They can unscrew bottles, solve puzzles, and some cultures even believe they can tell the future (like Paul the Octopus, who “predicted” the outcome of the 2010 FIFA World Cup). Some scientists think that octopuses were the first intelligent species on Earth.

But how are they so smart? Due to their nine brains, of course! But how these nine brains look, where are they located, and how they work is not widely-known information. But if you want to learn about octopus brains, you came to the right place.

In this article, we take a look at the fascinating facts about octopus brains, answer how many brains octopuses have, and dive into the details about their location, function, and looks.

Do Octopuses Have Brains?

Yes, octopuses have nine brains. There is one central brain between the eyes and nine collections of neurons called mini-brains in each arm.

Octopuses have unique anatomy. In addition to their blue blood and three hearts, octopuses have nine brains: the central brain in the head and eight mini-brains (one in each arm) that function as semi-independent organisms.^[1]

The central brain is between the octopus’ eye and acts as the main decision maker. The mini-brains act accordingly to the central brain’s demands, but each arm is capable of operating independently from the others.

The central brain essentially delegates tasks to the mini-brains.

Their eight arm-brains are also the reason behind their unique and complex arm movements.

For example, if the central brain says “search for food”, each of the mini-brains will receive a message and search for food independently.

What Do Octopus Brains Look Like?

The two types of brains look different. The central brain is a doughnut-shaped muscle mass located around the esophagus. The eight min-brains are dense concentrations of neurons and networks.

The two brain types are built differently. The central brain is structured more like a conventional brain, but the mini-brains are ganglia, a network of neuron clusters in each arm.

Central Brain

The central brain is a doughnut-shaped mass of muscle. The esophagus goes through its hole. It is situated between the two optic lobes.^[6]

Mini-Brains

Each mini-brain is a detached, dense network of neurons spanning the whole length of the arm. They are all connected to the central network.

Why Do Octopuses Have Nine Brains?

Octopuses have nine brains to help them navigate and to control their arms properly. Their high intelligence and maneuverability help them maneuver in small spaces.

The main reason for the eight mini-brains is to control each arm efficiently.

The nine brains also make octopuses highly intelligent. They are capable of working their way around man-made objects, such as unscrewing bottle caps. 

Some especially intelligent individuals are known to communicate with humans, such as grabbing and pulling them to ask for help.^[7]

Their intelligence helps them with the following tasks:

• Navigation
• Multi-tasking
• Maneuvering
• Awareness
• Puzzle-solving
• Communication
• Controlling eight different limbs

How Do Octopus Brains Work?

The octopus’ nervous system is decentralized. The majority of neurons are spread out in the arms. The central brain gathers information through sight and sends information to the arms, whereafter the arms act on these stimuli.

The central brain gathers and acts on information. The central decides what the octopus should do based on the octopus’ surroundings and condition. 

The information then travels through neurons (which are essentially messengers of the body) from the central brain to the mini-brains.

Here’s an example of how the octopus’ brains works:

The central brain senses hunger in the octopus, so it sends out signals for the arms to look for food. The arms feel around trying to sense food. If the octopus finds potential food (crab, mollusk, lobster), it sends out the command “grab”.

After grabbing, an activation wave travels through the ganglia from the grabbing point to the base of the arm. The base sends a signal back, meeting the aforementioned wave halfway. 

This activates a bending motion in the arms, raising the food to the beak.

In short, this is how the octopus brains work:

1. Central brain gains information.
2. Central brain sends a signal through neurons to the arms.
3. Arms gain signal and the appropriate behavior pattern is activated through the ganglia.
4. The mini-brains carry out the delegated task semi-independently.
5. Behavior pattern is continued until the task is finished or a new signal arrives.
6. If successful, an activation wave is sent to the base of the arm.
7. The base of the arm sends a signal back and meets the wave halfway.
8. Appropriate behavior pattern is activated.

Are Mini-Brains Fully Independent from the Central Brain?

No, the mini-brains don’t work independently. They are semi-autonomous, but they are still under the influence of the central brain.

In 2011, it was demonstrated that the central brain can take full control of the arms. The researchers gave the octopus a small glass maze with food inside. To reach the food, the octopus had to raise its arm above the water. 

The chemical sensors in the suckers (the main sensing tool of the mini-brains) do not work outside water, so the mini-brains had no way of knowing what was around the arm. The transparent walls enabled the octopus to look inside and control its arms directly.

A majority of the octopuses in the experiment successfully reached the food.

Octopus Brains Compared to Human Brain

The main differences between octopus and human brains are the amount, shape, location, function, brain-to-body ratio, and neuron numbers.

The human nervous system is centralized. Our brains directly control our conscious movements. 

For example, when we reach out and grab an object, our brain activates our muscles. All of the conscious motor processes are initiated and carried out by our brain.

The nervous system of the octopus is decentralized. Rather than a central body carrying out the full process, it sends signals activating behavior patterns. Once the signal is given by the central brain, the mini-brains, therefore the limbs, essentially have a mind of their own.

Comparison	Human Brain	Octopus Brain
Number	1	9 (1 central, 8 mini)
Shape	Crescent-shaped cerebral hemispheres, looks similar to a walnut	Ring-shaped central brain, looks similar to a doughnut, mini-brains are clusters of neurons alongside the arms
Location	Inside the cranium	Central brain around the esophagus and between the optic lobes, mini-brains in arms spanning their lengths
Function	Centralized, carries out task autonomously	Decentralized, central brain delegates tasks to semi-independent mini-brains
Brain-to-Body Ratio	2.5%	0.013%
Neuron Numbers	86 billion[8]	500 million

Conclusion

Octopuses have nine brains. They have a doughnut-shaped central brain around their esophagus and eight mini-brains in their arms. The mini-brains consist of a network of neuron clusters called ganglia. The majority of the 500 million neurons are in the mini-brains.

Octopuses are highly intelligent and use their nine brains to solve puzzles, navigate mazes, and maneuver in crevices. Their central brain delegates tasks to the mini-brains. The mini-brains work semi-independently. The central brain can override the mini-brains and the mini-brains can work for hours without a central nervous system.