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.
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.
Types of Octopus Brains
Octopuses have two types of brains: one central brain and eight mini-brains. The central brain differs from the mini-brains in location, function, sensing, and number of neurons.
Octopuses have an impressive brain-to-body ratio of 0.013%, comparable to other intelligent animals such as whales.
Most of their neurons (roughly 60%) are evenly distributed between the mini-brains, with only ten percent of the neurons being in the central brain. Interestingly, 30% of the neurons are located in the optic lobes. These are two extensions of the brain directly responsible for analyzing what the octopus sees.
|Between the eyes, wrapped around the esophagus
|Main task giver, sends signals to arms
|Receive signals from the central brain, act semi-independently
|Mainly through sight
|Chemical sensors, touch
|Number of Neurons
|40 million in each arm
The central brain is wrapped around the esophagus and it is the “headquarter” of the octopus’ thoughts and actions. It mainly gathers information through eyesight.
This is where basic thoughts like “move”, “eat”, and “grab” are formulated. But due to its high intelligence, the octopus is also capable of formulating complex thoughts with many conditions (like “go and search behind this crevice for the crab that just hid there”).
Regardless of the thought, the brain sends commands to the mini-brains in the arms. From then on, the arms semi-autonomously comply and work on the task given.
Here are some of the facts, workings, and characteristics of the central brain:
- Located behind the eyes
- Wrapped around the esophagus
- Gathers information through eyesight
- Sends signals to arms
- Delegates tasks to the mini-brains
- Contains about 180 million neurons
The mini-brains are dense networks of nervous systems each containing millions of neurons. These neurons are arranged in clusters called ganglia. Each octopus arm has twice as many neurons as a frog has in all of its body.
The mini-brains gather information via touch. The suckers contain chemical sensors that can distinguish between a wide array of molecules.
The octopus’ arm-brains act semi-independently of the central brain. They carry out tasks for the central brain, such as “search for food” or “grab that rock”.
The arms can function even detached from the central brain for several hours. Studies of artificially stimulated severed arms show that they still move in the same patterns as they do when attached to the body.
This does not mean the arms think for themselves but have a degree of autonomy when reacting to stimuli.
Here are some characteristics of the mini-brains:
- Dense networks of nervous systems
- One in each arm
- 40 million neurons in each arm
- Act semi-independently
- Carry out tasks the central brain delegates them
- Sense through touch
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.
The central brain is a doughnut-shaped mass of muscle. The esophagus goes through its hole. It is situated between the two optic lobes.
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.
Their intelligence helps them with the following tasks:
- 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:
- Central brain gains information.
- Central brain sends a signal through neurons to the arms.
- Arms gain signal and the appropriate behavior pattern is activated through the ganglia.
- The mini-brains carry out the delegated task semi-independently.
- Behavior pattern is continued until the task is finished or a new signal arrives.
- If successful, an activation wave is sent to the base of the arm.
- The base of the arm sends a signal back and meets the wave halfway.
- 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.
|9 (1 central, 8 mini)
|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
|Inside the cranium
|Central brain around the esophagus and between the optic lobes, mini-brains in arms spanning their lengths
|Centralized, carries out task autonomously
|Decentralized, central brain delegates tasks to semi-independent mini-brains
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.
What is the IQ of an Octopus?
An octopus’ IQ can be as high as 140. There is no reliable method to measure the IQ of animals, so the answers are only hypothetical. Every answer to this question has to assume that the octopus is turned into a human for the duration to take the IQ test.
Are Octopuses the Smartest Animals?
No, octopuses aren’t the smartest animals. Although they are highly intelligent, they are only the smartest invertebrates. The smartest animal depends on how smart is defined. Scientists generally name chimpanzees or dolphins to be the most intelligent animals.
What Other Animals Have Multiple Brains?
Apart from the octopus, there are many animals that have multiple brains. Octopuses aren’t even the animals with the most brains. Leeches (32) and silkworm moths (11) have more brains. Snails (3), squids (3), mosquitos (3), and cuttlefish (3) also have multiple brains, among other animals.