I've always found animal intelligence to be fascinating, particularly that of the cephalopods, some of which show some pretty remarkable talents for tool usage, mimicry, and pattern recognition.


Two-thirds of an octopus's neurons are found in the nerve cords of its arms, which have limited functional autonomy. Octopus arms show a variety of complex reflex actions that persist even when they have no input from the brain.

Perhaps this explains the feeling that while the the octopus is obviously intelligent it remains somewhat challenging to anthropomorphize.

I was thinking about designing a creature that lacked a central brain altogether.

I'm thinking of an octopus-like creature that used 8, or so, separate "brains" in concert. Each "brain" would be capable of maintaining the creatures basic bodily functions (cardiovascular, respiratory, digestive, and so on...), as well as being able to function independently or cooperatively with the other "brains".

Would such a creature design be feasible/believable for an animal level intelligence?

Taking this a step further, if we were to take this creature and anthropomorphize it a bit, would it appear to have some sort of dissociative identity disorder (split personality)? Would each decision would have to be run through committee or would it make more sense to have each brain take control from time to time?

(See also a different approach: What are the conditions in which a creature would evolve more than one brain?)

  • $\begingroup$ Sounds like starfish/sea stars. See also the famous Xenopsychology essay (which would be the basis of a great answer if someone has the time to do so without just plagiarizing it). $\endgroup$ – Leushenko Mar 19 '15 at 10:06
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    $\begingroup$ You may want to take a look at dolphins: they cannot completely sleep or they will stop breathing and die. To prevent that they have a -sort of- third hemisphere, and their hemispheres sleep one at a time. $\endgroup$ – Maxime Lucas Mar 19 '15 at 10:14
  • $\begingroup$ en.wikipedia.org/wiki/Blindsight_%28Watts_novel%29 $\endgroup$ – Mithoron Mar 19 '15 at 20:43
  • $\begingroup$ I think a lot of answers would be based on what one's particular theory of conicousness is. Integrated Information Theory (IIT) is one theory which is sufficiently scientific as to attempt to explore the meaning of such a divded conciousness, and how it might operate en.wikipedia.org/wiki/Integrated_information_theory biolbull.org/content/215/3/216.full $\endgroup$ – Cort Ammon Oct 3 '15 at 20:23
  • $\begingroup$ Vernor Vinge also had an alien race something like this in his Zones of Thought trilogy. At least, multiple brains = one person. His race was one of a pack of wolf-like creatures, but he comes up with some good analogies on how such a mind thinks, including partial death. Essentially each brain excels at certain tasks, the same way different lobes of our brains are good at different tasks, though it was more "skill" based (e.g. language, math, etc.) than sensory processing. $\endgroup$ – Draco18s no longer trusts SE Dec 2 '15 at 15:35

From an evolutionary standpoint, the main reason why you'd have separate brains or a decentralized brain as in the case of the octopus is to dedicate "brain" to certain actions without detracting from other processes. In other words, the central brain of an octopus would likely not have to think about how to grapple its prey, only that it wants to grapple its prey, and the nerve cells in its tenticles make the individual detailed decisions regarding how it could grapple its prey.

You could think of it as having a graphics processing core like most modern graphics cards have nowadays. While the CPU could perform the same calculations as the GPU, due to the quantity of calculations that must be performed, it is more efficient to specialize these calculations. And like this metaphor, the GPU doesn't act on its own accord, but rather it is the CPU that tells it to act. In the same way the nerve cells in the tenticles of an octopus specialize in dealing with how the tenticle should move.

It is difficult to imagine, but in a certain sense we do it too. The part of our brain that deals largely with automated actions like breathing and blinking our eyes is closer to our spinal cord and as such, those signals rarely arrive to our waking brain. Does this mean we can't control when we breathe or when we blink our eyes? No, however, to a certain extent, you could think of these functionalities as being specialized in order to not detract from thinking about other things. You may not realize, but the reason why you come up with ideas much more readily on the toilet is because your brain is not preoccupied with standing and, more importantly, balance. Thus you have more brain power to think about other things.

I'm thinking of an octopus like creature that used 8, or so, separate "brains" in concert. Each "brain" would be capable of maintaining the creatures basic bodily functions (cardiovascular, respiratory, digestive, and so on...), as well as being able to function independently or cooperatively with the other "brains".

Would such a creature design be feasible/believable for an animal level intelligence?

It wouldn't make much sense to have a separate brain just for cardiovascular, respiratory, digestive, etc. Monotonous tasks like breathing and beating of your heart don't require much "brain" to do. Based on what you find in nature, it is far more likely that you would have separate brain to govern movement and actions, which can get quite complex. Also, if one of these separate brains were in a less-protected part of the body and got injured, then if it handles movement of the limb, you could still survive. If it handled cardiovascular activity, you're dead. So perhaps there is also a good reason in terms of survivability that this tends to be what happens in nature.

Taking this a step further, if we were to take this creature and anthropomorphize it a bit, would it appear to have some sort of dissociative identity disorder (split personality)?

This, you don't see anywhere in nature, so we have no frame of reference. However it is also true that we can't just put them on a psychologist's couch and ask them what they're thinking, so we also can't know for sure. However speculating, we could look at ourselves. While it's true that we don't have truly separate brains, we have two hemispheres that work in synch to solve problems. The left brain tends to dominate in most people, and concerns itself with logic and detail while the right brain tends to deal with aspect and overall appearance (though recent studies suggest that this difference isn't as strong as initially thought).

The reason behind the fact that most people in their adult years still draw stick figures is due to the fact that the left brain, not knowing how to draw a person but thinking it knows anyway, forces control over the right brain which otherwise would have carefully and patiently studied and remembered how a person looks in order to draw effectively. What feels like you drawing a stick figure is actually your left brain saying, "Hey, back off, right brain, I know how to do this.. just make a circle and a stick underneath with a line for the arms and two lines for the legs.. DONE!" In fact the first step to learning how to draw well is dropping preconceptions about how to draw things and just trying to draw what you see. You may still have difficulty drawing doing so, but only because your right brain is practicing for the first time.

If our hemispheres were separate, due to the distance to send signals, it may not seem so much like you but more like your left and your right. This is just speculating, but our identity too might get split somewhat. However remember that evolution won't support a creature that can't "work," so despite this conflict in identity, they would have to get along well (no two-headed ogre stuff or nothing would get done).

Would each decision would have to be run through committee or would it make more sense to have each brain take control from time to time?

Returning back to the discussion of drawing, in that instance, the left brain just takes over. There is no consensus, and in a certain sense, there shouldn't be any, or you wouldnt' get anything done. Certain pathways tend to allow one hemisphere to have an edge over the other.

However this isn't to say that your hemispheres don't battle certain decisions out. The Rubber Hand Experiment is a classic example of such conflict. Your left brain knows the hand is fake, but your right brain sees and feels something different. When danger strikes, you're forced to come to terms with which hemisphere is right. Even though you know otherwise, you still get the same response as you would if someone were to try to hammer your real hand, because one of your hemispheres believed it were real. Usually when confronted with such a conflict, the signal that claims danger is the one that dominates (and for good reason). So to answer your question, likely each brain would formulate its own opinion on the matter and the brain with the strongest opinion would probably win over the others. However this is all very much speculative.

Check here for recommended reading on the subject. I hope that helps.

  • $\begingroup$ I just so happen to be learning to draw AND simulating a GPU in a Java application, and I can tell you that you make very good examples. $\endgroup$ – DaaaahWhoosh Mar 19 '15 at 13:45
  • $\begingroup$ The idea about the redundancy in brains, each being able to control basic function, had more to do with injury. If the creature lost one of its limbs one of the other brains could step in and control the heart and so on... $\endgroup$ – apaul Mar 19 '15 at 15:13
  • $\begingroup$ Very good answer though. I hadn't considered the left/right/brain-stem split. $\endgroup$ – apaul Mar 19 '15 at 15:15
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    $\begingroup$ With regards to dissociation and brain splitting, you might want to check out Split-Brained patients. The corpus callosum (connecting the two halves of the brain) is basically severed, but they don't actually experience changes in personality or suddenly get split-personality disorder. It's not exactly the same, but it's interesting to note. $\endgroup$ – Reliable Source Oct 4 '15 at 8:44

A creature with a decentralized brain could get rid of the standard idea of a nervous system altogether, and simply have brain tissue spread evenly throughout it's body, perhaps similar to the way fat is distributed throughout the human body.

This would mean no split-personality problems, because it is one big brain, and some redundacy - chop off it's head and it will have enough brain left to continue functioning (although, depending on brain structure, there could be some physchological damage, as seen in victims of severe head trauma).

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    $\begingroup$ This. there is no reason that decentralized brain means multiple brains / multiple personalities. A decentralized brain is one brain, decentralized. $\endgroup$ – kutschkem Apr 10 '15 at 11:46
  • $\begingroup$ True, but most people seem to think 'decentralized brain' means some kind of hive mind, with multiple individuals. I guess I fell into this misconception as well. $\endgroup$ – Ryan Krage Apr 13 '15 at 12:15

Animals like flies have less centralized nervous systems, and I think an extreme example is the box jellyfish: 24 eyes and no brain. The six distinct eyes at each corner have different dedicated purposes and together simple logic to combine them is all that's needed for navigation and avoiding the crowded tree roots it forages among.

The signal speed in a nerve is very low, which provides both reasons to keep things together and reasons to distribute. Consider the very large long-necked dinosaurs. Extending its neck vertically would starve the brain of blood, so the brain is the size of a walnut. Yet, the signal delay means putting reflexes necessary to balance and walk near the limb being controlled. Consider that mammals have reflex handling at the spine; that might be true for other vertebrates, and can develop complexity from there.

Since the walking, balance, tail swishing, etc were already distributed, the main brain could shrink under evolutionary pressure (the long neck and unique food source higher than others could reach) shifting function to other places.

Consider what might happen under similar conditions: the neck becomes just another limb, with local processing for the eyes and eating, but new layers of complexity that in vertebrates wrapped around each previous layer would grow in a second brain at the base of the neck.

Consider different biology too, to change the rules. If nerves with high speed information transfer existed, there would be less reason to centralize processing. Or, look at our optic nerve: it's not a simple wire, but an elongated processing pipeline that puts each end where needed but does the needed work along the way. The spacial transport is free since it needed to run through those steps anyway and they can be arranged in a line.

What if you took that to the extreme and had no brain at all in the sense of a big bump; processing occurs in the cables connecting the systems together. When more complexity is needed, instead of layering like us, they grow more 1-dimential filaments in rings attached along the main line.

Back to the colony organism idea: different specialized parts could occur as different phenotypes, like we have different organs with one genome. Different individuals would link up and combine "brains" as well as functions. An intelligence could change its being by swapping parts, as with Verner Vinge's multi-body beings.


Larry Niven had a species like this - the Jotoki.

The idea is that originally they are several distinct animals. Then as part of their lifecycle, 5 animals join up, creating a collective animal with five semi-independent brains (kind of like a giant starfish).

Per the split personality question: I think one of the reasons the Jotoki had five segments was because that's an odd number, it prevents split decisions. So as soon as at least three brains agree on something, they can act on it. Keep in mind though that a creature that developed like this is probably going to have a different view of individuality than humans. The brains also "grow up" together, and will likely all be friendly simply because it's required for survival.

One other advantage of the multi-brain system that he also brings up is sleep. The Jotoki "sleep" in cycles, leaving at least three brains active at all times while two rest. So the creature in total can be active 100% of the time.

  • $\begingroup$ Also related is the g'woth. Though, a g'wo individual is fully sentient and the multi-mind composite is not physically functional. I believe the g'woth is nevertheless multi-brain even on the individual level as they are described as being evolved from colonies of worms (that is, each worm colony makes up one "starfish") $\endgroup$ – slebetman Mar 19 '15 at 20:56

"Intelligent Design": Such creature could be constructed. It's about impossible for it to develop through evolution, simply because brain requires a lot of energy to operate, and that much redundancy in a single organism is much less "survivable" than if all the brains belonged to separate organisms. Octopuses work, because their sub-brains are highly specialized, each operating one tentacle. If all brains were "general purpose" though, duplicating their capabilities, that would be a waste.

It's a design that would work, but wouldn't work well "in the wild", requiring more nutrients than competitors while not possessing any major physical benefits that would help finding these nutrients.

If you go in this direction though, you might want to evaluate the idea of multiple organisms that can live independently, but can clump together and create neural connections between each other; special areas of skin that provide neural connectivity to such areas on the skin of another.

That could have developed naturally, say, through a joint in the body that requires neural communication, but not all the time, and at one point the two halves separate entirely. These creatures could "exchange memories", "brainstorm" and stick together until they all agree on a pack tactic or activity, then either proceed as a bulking mass to engulf a large prey, or dissipate into a swarm following pre-loaded instructions and foraging for plankton or insects. It is quite possible over time the big mass form could develop intelligence, and its mental capacity would be proportional to the number of the small creatures.


a creature that lacked a central brain altogether.

That sounds a lot like:

"All these centuries we thought starfish wandered aimlessly, a sort of aquatic Roomba. We thought so right up until somebody made time-lapse movies, and found that starfish have an active social life, and dominance contests, and are such deadly hunters that when one comes around the snails all flee as fast as each one's little head/foot can carry it. (Bugs hunt, too, but starfish have no brain.)"

-- Nathan Myers http://advogato.org/article/917.html

According to the fictional book "Starfish" by Peter Watts,

"A starfish," Acton tells her, "is the ultimate democracy." ... "So there's nothing to coordinate the tube feet, they all move independently. Usually that's not a problem; they all tend to go towards food, for example. But it's not unusual for a third of these feet to be pulling in some other direction entirely. The whole animal's a living tug-o-war. Sometimes, some really stubborn tube feet just don't give up, and they literally get torn out at the roots when the others move the body someplace they don't want to go. But hey: majority rules, right?"


Why limit yourself to eight brains when you can have eight millions? ;)

Take a look at the Portuguese Man-o-War. It is not a single creature, but a colony of small organisms, theoretically independent but so specialized that they cannot live if separated from the rest of the colony.

Imagine something like that, but created by more advanced organisms, like ants or bees which evolved from their nowadays state of eusociality into a much more integrated form of a superorganism. In fact, even now in some contexts we can talk about an anthill as an organism of its own. For example, ants as a colony may perform tasks much more complex than one ant is able to comprehend, like finding the best way to the food source by leaving pheromone trails which are strengthened when they are more often travelled and expire when they are not: Ant Colony Optimization Algorithms.

Let's take it into another level: an "anthill" of creatures so integrated that they act as cells of a single organism, but each with their own tiny brain communicating with each other via pheromones. As such, they would probably be unable to move far away from each other or the link gets broken, so in the search of food the "anthill" would release lines of these "ants", each one moving just after another and being able to process and pass pheremone signals, so the anthill - acting as the superbrain formed from all the "ants" which stayed behind - may control this weird flimsy tentacle. As it is with several species of ants we know about, the anthill itself might be just a big group of these "ants" holding to each other and could do without any structure made from earth or leaves. This way the whole "anthill" would be even able to move if necessary.

Not exactly what you had in mind probably, but when I started to develop thw idea, I wasn't able to stop myself :)


There are many animals and living organisms with no CNS ("brain"). Various alternative control methods are implemented.

Slime molds - We actually have no effing clue how this really works, but basically a bunch of cells get together and act like a single organism with a reasonably complex brain that doesn't exist - probably pheremones, electrical potentials, or carefully constructed individual reaction chains leading to complex swarming behavior are to blame.

Plants - Basically they get on fine by cutting out silly brains and getting directly to the stimulus detection and response loop. Their brain is their body, and vice versa.

All this brainless talk is to point out that generally, nature takes advantage of the emergent properties of her systems whenever possible (because evolution is lazy and always wants to make the most of the least genetic change). If an animal has several brains, or a brain that IS it's body - command and control decisions are likely to be the emergent property of each of these systems making its own decisions independently, independently taking in stimuli from the decision results of the other brains, such that in fact the apparent unity of the system is only a happy accident and not a well-defined thing.

Really when you get right down to it, brains in general work this way - ours are all squished together, but figuring out how one part works in concert with another to give rise to our unitary conscious experience is such a profound mystery it has been given its own name: the Binding Problem.


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