how many brains does an octopus have

When we think about an octopus’ and its brain, we do not get the same simple answers we would with humans. An octopus’ brain is simultaneously defined as both one and nine. We will see why it is considered so; it is one of those creatures that challenge our current views of what constitutes a central nervous system.

One Central Brain: Command & Control Center

The central brain of the octopus is found in a donut shaped ring of tissue surrounding the esophagus directly behind the eyes of the octopus. For an invertebrate, the development of this central brain is impressive. It houses approximately one-third of the total neuron count for the octopus; approximately 60 million. To give you an idea of scale, a mouse has 71 million neurons in its entire brain. As researchers have identified via work done by Dr. Jean Boal at the University of Maryland, this central brain is capable of performing complex cognitive functions such as learning, memory and problem solving (such as navigating a maze). High level decision making is performed by the central brain as well.

The “Nine Brains”; Ganglia Found in Each Arm

This is the basis for defining an octopus as having “nine brains”. Each of the eight arms found on an octopus contain clusters of neurons, referred to as ganglia. In reality these ganglia operate very much independently as mini-brains. In fact, approximately 2/3rd of an octopus’ total neurons (approximately 300 million), are housed throughout the eight arms. So each of the eight arms has approximately 50 million neurons – equivalent to the amount of neurons in the entire brain of a small mammal.

Why Decentralized Processing Allows Each Arm to Act Independently

The decentralized structure of an octopus’ nervous system allows its arms to act autonomously. Each arm can functionally perform tasting, touching and movement on its own, typically without the direction from the central brain. If an octopus is using an arm to retrieve food from a crevice, it may take action to explore, locate a possible meal item, and capture it – all while the central brain is engaged in separate activities (e.g., monitoring a predator).

As a result, the processing occurs efficiently across multiple locations.

Studies completed by neurobiologists such as Dr. Binyamin Hochner at the Hebrew University of Jerusalem demonstrated that once an arm was severed from the rest of the octopus, the arm continued to respond to stimuli and attempted to hold onto objects for a short duration after being removed. It should be noted that the severed arm is not “thinking”, but rather executing pre-programmed motor and sensory responses due to its own localized neural networks.

Suction Cups Have Sensory Capabilities

Each of the numerous suction cups that line an octopus’s arms contain chemoreceptors and mechanoreceptors. This enables the suction cups to independently sample their surroundings and respond accordingly. The neural connections directly below each suction cup enable local processing of sensory input to assist in contributing to the independent actions of the arm.

Communication Between Central and Arm Brains

Although the arms can function separately, there exists a continuous communication between the central brain and the arms. The central brain gives the general instructions – “get food”, “go to that rock”, etc. – and the arms provide the detailed execution of said tasks. Additionally, as each arm receives feedback from the sensory inputs, this data is communicated back to the central processor.

Think of a chef directing their apprentice – “prepare dinner”. The apprentice(s) (the arms) now have freedom to chop vegetables, make sauces, cook meals, etc. and report back only on larger issues or status updates. The distributed intelligence provides for great flexibility for complex behaviors (manipulation of objects, camouflage of skin, etc.) utilizing extreme dexterity.

Advantages Provided By Distributed Intelligence

There are three primary reasons for evolution developing distributed intelligence in octopuses:

Redundancy: With some areas of the nervous system damaged, others can compensate for lost functionality.
Efficiency: By completing multiple tasks locally within each arm, the central brain can dedicate time to higher order problems.
Speed: Local processing in each arm provides rapid response times to local stimuli; ideal for a predator/prey relationship dependent upon quick response times and camouflage abilities.

Comparison Between Octopuses And Other Cephalopods

All cephalopods (squid, cuttlefish) exhibit advanced levels of neurological development; however, none approach the level of decentralized intelligence observed in octopuses. Although squids and cuttlefish do have significant amounts of neuronal networks present in their tentacles/arm segments; their ability to process independent data appears less compared to those of an octopus. It can be inferred that this specialized form of intelligence reflects their differing environmental niches and behaviors, with octopuses displaying more elaborate forms of manipulation and exploratory strategies within their benthic habitats.

Misconceptions Surrounding Octopus Intelligence

It is understandable that people may develop misconceptions regarding the intelligence of an octopus based on statements referring to “nine brains.” While it is true that octopuses demonstrate incredible intelligence – including problem-solving, observational learning and even utilization of tools – it is essential to understand that their type of intelligence differs dramatically from our own. It is not merely nine human brains working together. Rather, it represents a uniquely efficient method for distributing information processing capability within their specifically designed anatomy/environment.

Frequently Asked Questions

Do each of an octopus’ arms retain memory?

While each arm possesses a substantial capacity for processing neural activity; it is unclear whether each arm retains “memory” similar to that experienced by humans. They certainly can locally learn new motor patterns and sensory responses, thereby adapting their movements.

Will a severed octopus’ arm continue to function independently?

Yes; although briefly. A severed octopus’ arm will continue to respond to stimuli, manipulate objects, and move for a brief period post removal. Eventually, however, the arm will cease to function due to degradation of the neural tissues supporting it without support from the central body.

Are octopuses more intelligent than humans because they have more “brains”?

Absolutely not. The concept of having “more brains” does not necessarily translate to increased intelligence when considering species possessing drastically different types of neural arrangements. Octopus intelligence is complex and tailored for their aquatic environment; however, it operates under entirely different principles than those utilized by humans.

Approximately how many neurons are contained in an average octopus?

It is believed that an average octopus contains approximately 360 million neurons. Approximately one-third are found in its central brain; approximately two-thirds are distributed among its eight arms.

To answer your question simply, an octopus has one main central brain that processes high-level commands; however, each of its eight arms contain smaller ganglia that can be thought of as independent “mini-brains”. The unique structural organization allows for incredible dexterity and sensory capabilities enabling adaptations necessary for surviving in their underwater realm.