What exactly is the Positronic brain coined by Asimov?

I encountered this term several times without having a clear understand of what it means and what "positronic" mainly means.

Can you clarify it, please? :)

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    See also Positronic brain on Wikipedia. Dec 19, 2011 at 11:41
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    It was handwaving by a really good writer. I was thinking about this the other day ... in semiconductor theory, a conductor can be saturated with electrons, and the repulsion causes them to maintain a specific pattern. A space can exist that has no electron, and it acts as if it is something real with a positive charge. It's called a hole. There's a whole way of looking at semiconductors where the holes are considered to explain the action of the semiconductor and it refers to "hole current". I got to thinking that in a way, this is the 'positronic' system that Asimov was using. Jun 18, 2016 at 3:00
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    It's like a negatronic brain, only more upbeat. Aug 3, 2023 at 16:54
  • It's like an electronic brain, except that it immediately self-annihilates in a titanic matter-antimatter explosion. Aug 3, 2023 at 18:19

9 Answers 9


Asimov was very vague about the construction of these brains. Presumably they use positrons, which are antielectrons. Which would suggest they must have powerful magnetic fields. They are also described as being constructed of a platinum and iridium alloy.

Star Trek: TNG lifted the idea for Data's brain. While having nothing to do with Asimov, it does offer some insight into how others viewed his ideas. Same goes for the "I, Robot" movie, you can get some sense of what others think these things could look like.

Unfortunately, that's all the info there seems to be.

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    IIRC, Tasha Yar explicitly mentioned "Asimov's dream of a positronic brain" in an early STTNG episode. Incidentally, I'm not sure how positrons imply a particularly powerful magnetic field, any more than electrons would. Mar 5, 2014 at 18:52
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    @KeithThompson Electrons don't annihilate on contact with normal matter. Positrons do. The magnetic field is needed to contain the positrons. I suppose some alternative method could be used, but as far as known science the other option we know of is magnetic containment.
    – DampeS8N
    Mar 5, 2014 at 19:35
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    Additional Note: Positrons are used in PET scans. When the positrons annihilate they release gamma rays that the machine can detect in 3 dimensions.
    – DampeS8N
    Mar 5, 2014 at 19:36
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    I thought you were saying that the positrons would create a strong magnetic field, but actually you'd need a strong field to contain them. That does make sense. (The actual usefulness of using positrons in a computing device is extremely questionable, but it looks like Asimov just chose the name because it sounded cool.) Mar 5, 2014 at 19:38
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    Not just for that..he knew about "electronic brains" and wanted a quantum leap above that...so he flipped to positrons.
    – Oldcat
    Dec 10, 2014 at 0:02

Why “positronic”?

When I first began writing science fiction stories, the positron had been discovered only six years before as a particle with all the properties of an electron except for an opposite charge. It was the first (and, at that time, still the only) bit of antimatter that had been discovered, and it carried a kind of science-fictional flavor about it.
    That meant that if I spoke of “positronic robots” rather than “electronic robots,” I would have something exotic and futuristic instead of something conventional.
The Word I Invented, 1980

How does the positronic brain work?

[P]ositrons are very evanescent particles, at least in our world. They don’t survive more than a millionth of a second or so before they bump into one of the electrons with which our world is crowded, and then the two annihilate each other.
    I had a vision, therefore, of “positronic pathways” along which positrons briefly flashed and disappeared. These pathways were analogous to the neurons of the animal nervous system, and the positrons themselves were analogous to the nerve impulse. The exact nature of the pathways were controlled by positronic potentials, and where certain potentials were set prohibitively high, then certain thoughts or deeds became virtually impossible. It was the balance of such potentials which resulted in the Three Laws.
    Of course, it takes a great deal of energy, on the subatomic scale, to produce a positron; and that positron, when it encounters an electron and is annihilated, produces a great deal of energy on the subatomic scale. Where does that positron-producing energy come from and where does the positron-annihilation energy go to?
    The answer to that is that I didn’t know and didn’t care. I never referred to the matter. The assumption (which I didn’t bother to state) was that future technology would handle it and that the process would be so familiar that nobody would wonder about it or comment upon it—any more than a contemporary person would worry about what happens in a generating plant when a switch is flicked and a bathroom light goes on.
The Word I Invented, 1980

What is the positronic brain made of?

When I wrote my first few robot stories in 1939 and 1940, I imagined a “positronic brain” of a spongy type of platinum-iridium alloy. It was platinum-iridium because that is a particularly inert metal and is least likely to undergo chemical changes. It was spongy so that it would offer an enormous surface on which electrical patterns could be formed and un-formed.
Cybernetic Organism, 1987

Additional sources

The mere fact that I talk about positronic robots and say they are guided by the Three Laws of Robotics has no actual predictive value from the engineering standpoint. Imagine, for instance, a discussion between an interviewer (Q) and myself (A).
    Q. What is a positronic robot, sir?
    A. One with a positronic brain.
    Q. And what is a positronic brain?
    A. One in which positronic shifts take the place of the electronic shifts in the living human brain.
    Q. But why should positronics be superior to electronics for the purpose?
    A. I don’t know.
    Q. How do you keep your positrons from combining with electrons and forming a flood of energy that will melt down the robot into a puddle of metal?
    A. I haven’t the vaguest notion.
    Q. For that matter, how do you translate positronic flows into the “Three Laws of Robotics”?
    A. Beats me.
    I’m not ashamed of this. In writing my robot stories it is not my intention to describe robot-engineering in detail. It was merely my intention to describe a society in which advanced robots were common and to try to work out possible resulting consequences.
Future? Tense!, 1965

It was usually called the “positronic robot” series, because the electric currents in the brains were flows of positrons rather than electrons. I did that just to make the brains sound part of a futuristic technology, but some of the less sophisticated readers thought that this was based on sound science and would ask me to give them additional information on how it worked.
In Memory Yet Green, 1979

[W]hen in 1939 I began to write robot series, I gave my robots “positronic brains” as a glamorous science fictional variation of the flat and uninspiring “electronic brains.”
Opposite!, 1987

Since I began writing my robot stories in 1939, I did not mention computerization in their connection. The electronic computer had not yet been invented and I did not foresee it. I did foresee, however, that the brain had to be electronic in some fashion. However, “electronic” didn’t seem futuristic enough. The positron—a subatomic particle exactly like the electron but of opposite electric charge—had been discovered only four years before I wrote my first robot story. It sounded very science fictional indeed, so I gave my robots “positronic brains” and imagined their thoughts to consist of flashing streams of positrons, coming into existence, then going out of existence almost immediately. These stories that I wrote were therefore called “the positronic robot series,” but there was no greater significance than what I have just described to the use of positrons rather than electrons.
My Robots, 1987

[I]n 1939, at the age of nineteen, I determined to write a robot story [...] Since I needed a power source I introduced the “positronic brain.” This was just gobbledygook but it represented some unknown power source that was useful, versatile, speedy, and compact—like the as-yet uninvented computer.
Introduction: The Robot Chronicles, 1990

From Frederik Pohl’s blog:

Why were they positronic? I asked him that once and he said, “Because the positron had just been added to the list of particles and no one knew what it could and couldn’t do.”
Isaac, Part 3 of quite a few, 2010


Essentially it's a plot device used to mean "unknown future technology".

Asimov deliberately didn't talk about the technical aspects of his robots, so that he could focus on the characters involved. This is one of the main reasons why his stories written in the 1940s and 1950s aren't too dated; because he didn't talk about transistors and vacuum tubes, he talked about fictional technologies like the positronic brain.

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    Agreed. He was more interested in the relationship between mankind and robots, not how they worked.
    – Michael
    Jan 13, 2011 at 23:56
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    He was also fascinated by logic and rules, and how they could be used and misused: like the Three Laws of Robotics. Mar 24, 2011 at 0:53

I remember reading somewhere Asimov saying that that when he was writing his first robot stories, the Positron had just been discovered (1932) and so it was a new cutting-edge idea.


Asimov never explained in too much detail any of the technologies he used on his works.

The positronic brain is the best example of it. There is an interview on the 70's (when he worked on real science papers) when he defined an aproximation of a positronic brain:

"It's a brain made by the men, so any brain, ever ours is positronic"

I always thought that a positronic brain is a brain designed by men, not by "god". That's the best aproximation that I can think of


"Positrons travelling about a sponge like substance" is, I believe, the way it was expressed.


According to The Caves of Steel, this brain has very interesting specifics. It cannot be constructed without the Three laws, because no math theory of such brains existed. The only math theory that exists, according to the novel, only allows the construction of positronic brain that follows the Three laws. It is impossible at hardware level to do otherwise (such constructions are unknown).

Later in some works Asimov described possible workarounds like introducing the Zero law. But no math theory for it was ever developed, therefore it can be seen as a bug in R. Daniel brain, and nothing more.

  • In comes the Caliban trilogy, with gravitonic robot-brains where a robot can have no laws builtin (Caliban himself) or an entirly different set (the New-law robots). Sep 18, 2013 at 13:00
  • Asimov created the three laws just so he could write stories about robots that are forced to circumvent them. Jun 18, 2016 at 3:02

I'm sure that, yes, Asimov wanted to use a non-trivial name for the computer and the word 'electronic brain' was flat and trivial. 'Positronic brain' added a glam into his novels and made it possible to weave many novels to that 'positronic' which combine together to a fictionary story for humanity 20.000 years from now (see his 'Galactic Empire'). The term 'positronic' was the key needed to make 'real' his stories about the salvation of humanity based on the fact that he was atheist.

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    Could you edit your answer to make it clearer what the positronic brain was and not just why it was invented
    – Edlothiad
    Jun 21, 2017 at 17:53

That is correct, he is used positronic because it was generalistic and hip at the time. One must avoid use of real-world machines or metrics in sci-fi else they become quickly outdated even if you think it wouldn't. Case in point, the android Data said he could perform 60 trillion calculations per second, which was bionicle in 1987 but today hardly impressive as supercomputers today exceed that figure by 100x easily.

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    Can you offer an in-universe explanation of what Asimov meant by the term positronic? He used the term extensively, and it was also used in reference to Data's brain, although that definition would rest within a different universe. Providing an in-universe answer, if available, might go further towards answering the question. Mar 19, 2016 at 5:50

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