One of my characters in a super hero setting can have their body turn into slime. By quirk of their power, they are able to process thoughts with their entire body, effectively turning their entire body into a brain, leaving them paralyzed while in "thinking mode".

My question is, what would be the effect of increasing brain mass in such a way? Would the person be able to think faster or process thoughts in parallel? Or would it actually be worse overall? I understand that brain power depends a lot on the shape of the organ, so assume everything increases proportionally.

Edit: If just increasing size and mass doesn't help, what properties the slime form would need to have to lead to an increase in 'brain power'?

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    $\begingroup$ I would suggest keeping the specific to only one particular topic. Stick to the part about thinking faster and focus on that. If there's more to the question then you can always ask a follow-up question later. $\endgroup$ Mar 10, 2022 at 2:31
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    $\begingroup$ Brain power is about more than simply the mass of the brain, much like how computational power is not the same as size. Computers used to be massive, but their calculating power is nothing compared to the phones of today. In a similar way, brains are not about mass but about the connections that are forged. $\endgroup$ Mar 10, 2022 at 2:33
  • $\begingroup$ One problem I have with the question is how is thinking defined. The brain never stops functioning. It never stops processing & analyzing. Many people can think of a problem, but not immediately develop an answer. The answer comes to them later after either sleeping or doing something else & thinking about something else. While all this is occurring, the subconscious works in parallel thinking of an answer. $\endgroup$
    – user81881
    Mar 10, 2022 at 4:33
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    $\begingroup$ This is a great concept but we can’t pack all your problems into one question. Try to focus this on one issue, perhaps on “processing power”, and put the rest into separate questions. $\endgroup$
    – Vogon Poet
    Mar 10, 2022 at 4:57
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    $\begingroup$ I dont understand why people have a problem with this question? It pretty much boils down to "if I increased my brain mass to be equal to my weight, how smart would I be and what kind of processes could my brain perform?". $\endgroup$
    – Demigan
    Mar 10, 2022 at 8:20

6 Answers 6


Unfit brain

Let's skip by the problems of having only a brain, like the huge energy requirements, transport if nutrients and waste, filtering, immune and all that. We assume this still works magically and the whole body is a working brain.

As mentioned in the question, shape is very important. We can see stark differences in brain mass and processing. Birds are a good example of well optimised brains for their size. Humans have a still unoptimised brain for the most part. Brain stem and cerebellum are quite old and optimised, but the youngest structures like the frontal cortex have grown incredibly fast, but not very dense. They will probably develop much more sulci and gyri, the ridges and canyons that make the distinct brain structure, as well as increasing mass. The take away is simple. Increasing brain mass means barely anything if it isn't optimised. A slimy brain seems unoptimised from the word go(ey).

More damning is that brain structures are specialised. You can't have just random bits of brain. Each has a specific function with specific connections. The brain miracle is how it's still so plastic in receiving information, learning and making decisions on this information. Adding the rest of the body as a brain will just lock up the normally functioning brain with all the random signals.

Even if they grow into specialised structures theres two more big hurdles. One is that most brains have limiting effects on others. Interesting research with electrical (over) stimulation shows you can make one brain half (part) numb, barely functioning. The other brain half won't be inhibited anymore, causing huge increases in it's function. As an example, people who sucked at drawing suddenly could make beautiful artwork.

The other problem is electrical induction. A study showed that if neurons are packed too close together with a high volume can cause too much accidental signals in surrounding neurons. At a certain point this will make communication between neurons troublesome, if not impossible. Imagine it as sending morse code. Sometimes a random extra signal will still make an understandable message. If this increases to 20% of your message and at random, I'll become illegible.

Making it work

To make a 'slime brain' work you need to rework the whole brain. The advantage is that you do not rely too much on speed anymore. Movement requires quick decision making and making the move. Thinking about complex mathematical problems or why life, the universe and everything else us 42 can use relatively slow communication between specialised brain structures.

So make highly specialised brain structures. The compactness of the brain doesn't need to increase, as only the mass counts. Not compacting is in this case advantageous to prevent spontaneous induction. The corpus callosum must change to facilitate much more connections to each structure cleanly and where appropriate.

The resulting brain power is undetermined and highly dependent in the structures implemented. If it's all visual stimuli processing for the full spectrum with new and innovative ways of recognising your surroundings you do not have higher calculation power. If you also don't have eyes, or same human eyes, most of it will be useless.

Even if you do all calculus or something similar it us difficult to say the increase. Most likely it'll be something exponential, but it is impossible to tell. Einstein revolutionised many fields while his brain wasn't extraordinary. Some people with more brain mass can't even learn a language.

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    $\begingroup$ +1 Could you please also post some links? The study with the uninhibited half-brain and drawing seems really interesting! $\endgroup$
    – Ivana
    Mar 10, 2022 at 12:46
  • $\begingroup$ This mostly seems like an explanation of why it wouldn't work the first time (and might even be a traumatic shock), what might go wrong as they practice; then why it might take hours (or longer) once they know how, and why they would have to choose between (possibly surprising) different set-ups even after becoming proficient. $\endgroup$ Mar 10, 2022 at 15:16
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    $\begingroup$ I too like would like a citation on the drawing study, because it sounds like complete nonsense. $\endgroup$
    – Harabeck
    Mar 10, 2022 at 16:29

If this superhero can either think or act while in slime form, then they won't be able to do anything. Mobile creatures that don't function using simple, hardwired reflexes need a brain to be able to decide what to do. Organisms as complex as humans need their brain for all movement other than their heartbeat. So, for this slime-hero to not think means that they won't be moving. To be unable to move while thinking means that they won't be moving.

Either way, they're stuck.

Of course, you could allow a progressive change from moving to thinking, so the character could either be strong, fast and dumb, or slow, weak and smart, or something in between. That might work.

As to the relative brain power between slime form and normal form, let's look at some numbers. Normal humans have approximately:

  • 86 billion neurons in the brain.
  • 7000 connections per neuron
  • 602,000 billion connections total
  • 30,000 billion cells total

In slime form, there are approximately:

  • 30,000 billion cells
  • 26 connections maximum per cell assuming cubic packing and both face and vertex connections
  • 780,000 billion connections total

Since it is the number of connections that makes for processing power, slime-form has 130% the number of connections that the normal form has.

So, naively, we could say that slime-form has 30% more intelligence when fully dedicated to processing rather than movement. It probably doesn't actually work that way, since the number of connections per cell is lower in slime form.


Size Doesn't Matter

The brain of a Sperm Whale is five times larger than that of any human.

Barring hither-to unknown levels of intelligence in cetaceans, it's fair to say that we're smarter than them.

What's important is complexity. Our ability to form complex neural connections and pathways is contingent on having a very dense structure with a lot of surface-area for connections to form across.

If you transformed yourself into 100% brain-tissue, you'd run into a major problem.

Brain tissue is not unspecialised. You can't just add more of it and be smarter.
It's how you use it that makes the difference, which should be intuitively obvious given that two people with roughly identical brain-mass can be so wildly different in intelligence!

If you just turned yourself into 150 pounds of neurons, you wouldn't be thinking, you'd just be a blob of neural tissue that does nothing.

What's needed is for the new brain tissue to be configured as part of the transformation.

Think of it like a computer, or maybe its software.

You can't just add more code. It has to be deliberate and reasoned and connected in the right ways or it simply doesn't work.

A brain is a massively complex electrochemical computer and adding more neurons doesn't really help much.

Properly done, a larger amount of brain-tissue would provide room for a great deal of complex processing and simulation beyond what's normal for a human (and don't underestimate how much that really is! Human brains are amazing) But you'd need it to be linked up properly, and structured for the task.


A brain isn't worth much if it has no connections

The problem is that, while your character can transform their entire body into brain-matter, the ability for a brain to think is dependent on its neurons having pre-existing connections with each other, and these connections can only form while it is functioning as a brain. The best-case scenario when your hero first transforms into a slime is that they still have their functioning human brain somewhere inside their body and a basic pre-existing neural net that allows it to move, but the rest of the body is just random neurons which are useless for any kind of thinking.

But it can form new ones

If the magic allows it, perhaps they might be able to learn things in slime form and "store" the connection data somehow when they transform back into a human. They won't be able to use those connections in human form, but they might be able to re-establish them once they re-slimify. Over many years, if they spend enough time living in slime form, the slime form might eventually become super-intelligent since it has a bigger brain to work with.

This super-intelligence will probably manifest mainly as an improved ability to store large amounts of information, but their ability to think more quickly will be limited since the connections per neuron are probably around the same as in human form. Still, having the ability to store large amounts of data might allow it to develop a better understanding of the world than a human would have.

Dr Jekell and Mr Slime

This will create an interesting situation, since it is not only knowledge that is stored in the brain, but personality as well. Their slime form may wind up with an entire alternative personality, which might "hear" the human personality as a "voice in its head" - since the entire human brain is functionally a tiny part of its body. While in human form, the slime personality will be effectively "frozen"; the human will be able to make their own decisions but will be unable to access the slime's super-intelligence.


The human brain isn't set up to be massively expanded, but it is set up to network with other brains. as conjoined twins prove.

As such, the easy way for the slime brain to work is to have it work as multiple personalities. They can have different regions of brain which can independently focus on different things and solving problems.


Human brains are already large.

Comparing with other animals, human brains are much larger than one would expect considering the body size.

The ratio of brain weight to body weight is about 1:5000 for fish, 1:220 for birds, 1:180 for mammals and 1:50 for humans (highest).

Bigger brains are smarter, but not by much

As told in this article, "The effect is there," says Nave, an assistant professor of marketing at Wharton. "On average, a person with a larger brain will tend to perform better on tests of cognition than one with a smaller brain. But size is only a small part of the picture, explaining about 2 percent of the variability in test performance. For educational attainment the effect was even smaller".

One of the notable findings of the analysis related to differences between male and females. "Just like with height, there is a pretty substantial difference between males and females in brain volume, but this doesn't translate into a difference in cognitive performance," Nave says.

Brains of smarter people have bigger and faster neurons

As told in this article, the scientist found that cells from people with higher IQ have longer, more complex dendrites and faster action potentials especially during increased activity. With computational modelling they could also show that neurons with larger dendrites and faster action potentials can process more information coming in and can pass more detailed information on to other neurons.


Make bigger and faster neurons, while increasing the size of brain only a little.

  • $\begingroup$ Ok but what if we assume that the extra mass added acts like the rest of the brain mass? So lets say you have a genius level IQ and now you add +/-60 to 70kg of brainmatter. What would its effect be? Something like a 100% increase in brain capacity or could you compartimentalize it and have +/-50 brains worth thinking independently about problems? $\endgroup$
    – Demigan
    Mar 10, 2022 at 10:12
  • $\begingroup$ Size and mass of Einstein's brain and brain of a dumb idiot are almost same. What matters is probably something else. $\endgroup$
    – imtaar
    Mar 13, 2022 at 8:53
  • $\begingroup$ still doesnt answer the question, it just dodges it. $\endgroup$
    – Demigan
    Mar 13, 2022 at 13:22

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