Suppose we've got one character, who for whatever reason (handwave.gif), has around a ~5ms reaction time (20-40x regular people's). That's enough to be many, many times faster than the rest of the population.

What kind of interesting stuff could this character do, besides the obvious trope of being a fighting machine? How useful would this actually be?

And would there be any feasible way that someone else could figure it out (maybe by throwing stuff at them)? If someone else witnessed something unbelievable, what do you think their reaction would be?


  • Modern Earth is the setting
  • The reaction speed is with regards to audio/visual/touch stimuli, etc.
  • The character has an average movement speed, meaning they can't just move their arm out of the way at 400mph (so dodging bullets close-range is probably still out of the question)
  • Perception of time is at the same rate as other humans (not "seeing/living in slow motion"), unless that's required for this to really work.

To clarify: Here, reaction time is the time from the arrival of the stimulus to the beginning of the response action. As an example, if the person saw a car coming at them, they would start moving 5 milliseconds after the light from that car arrived ath their eyes, but probably take hundreds or thousands of milliseconds to actually get out of the way.

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    $\begingroup$ Anyone whose eyes could capture and brain could process in a capacity allowing a 5ms reaction time would almost certainly be experiencing time in a different way than normal folks. How we perceive time is a result of these things, after all. So I don't think you can give a super reaction time and then rule out a difference in time perception. It's like saying "my character's eyes are more sensitive to light, so he can see better in the dark, but, by the way, they aren't more sensitive to light, so he is fine in daytime." One results in the other. $\endgroup$
    – MarielS
    Commented Apr 26, 2019 at 2:55
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    $\begingroup$ The difference might be small, hard to say exactly what the effect would be, but there would be a difference. Here's a fun article I found when I was looking at reaction time earlier. It's not necessarily directly related to your question, but you may find it informative. It talks about how different creatures currently already do have slightly different perceptions of time. dailymail.co.uk/sciencetech/article-2685860/… $\endgroup$
    – MarielS
    Commented Apr 26, 2019 at 2:58
  • $\begingroup$ Edited to include the reaction time definition. The person isn't any faster than anyone else once they've started reacting. $\endgroup$
    – user45266
    Commented Apr 26, 2019 at 4:19
  • $\begingroup$ What does broken mean in this context? $\endgroup$
    – kingledion
    Commented Apr 26, 2019 at 13:02
  • $\begingroup$ Thanks for the edit. I've retracted my VTC. $\endgroup$
    – JBH
    Commented Apr 26, 2019 at 13:15

3 Answers 3


What they need in addition.

Better eyes. The eyes refresh somewhere between 20-60 hertz which is 50-17ms. Their eyes will need to be notably faster so they can react to things.

Faster thinking. Humans can take two seconds to react to novel stimuli, because the brain takes a while to process the information and gauge an appropriate response. 200ms for a normal human reaction time is for a completely instinctual response. They'll need to think faster than a human so they can do cool reaction things.

Faster nerves. Nerve impulses move around 100 meters per second, so it would take 10-20 ms for a signal to reach body parts. Their nerve signals need to be noticably faster.

Applications of fast reaction times.

Fighter pilot. Gamer. Martial artist. Driver. Race car driver.

Any job involving fast movement around fast objects will work well for someone with extremely fast reactions.

Drivers will be able to pull off much more extreme maneuvers. Fighter pilots have much faster reactions than most humans which is important when flying around at immense speeds. They'll be able to pull off more extreme tricks and faster turns and twists because they'll have precise control of their vehicles.

Anecdotally, from my experiences with such people, they can often pull off fast reaction tricks like grabbing a cup when someone knocks it off a table or killing a fly.

Gamers need to synthesize a lot of information very quickly and press a lot of keys and evaluate situations tricky to perform well. Fast reactions will help a lot with being an awesome gamer.

Martial artists need to predict their opponent's movements extensively. If they can instead instantly react, they'll make far less errors and be much better equipped to handling fights.

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    $\begingroup$ Just to make a point, refresh rate is a popular and completely meaningless way of trying to explain the abilities of the eye. Your eye isn't digital. it has no "refresh rate." Air force pilots have successfully recognized planes flashed before them in 4.5 ms. This is because the idea of refresh rates and FPS when applied to the analog human brain doesn't mean much. Now, how quickly we can react to what we see and whether you're judging the beginning or the end of the reaction... that's a very different story. $\endgroup$
    – JBH
    Commented Apr 26, 2019 at 3:12
  • $\begingroup$ Could you elaborate on the examples of real-world applications you listed? I get that the driving would probably be helpful, but to what extant and why? Same for the other occupations/activities. $\endgroup$
    – user45266
    Commented Apr 26, 2019 at 4:21
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    $\begingroup$ @JBH the picture was displayed for 1/220th of a second. That does not mean it was recognized in 1/220th of a second. The idea of 'refresh time' is the time the rods and cones retain last image. When we stare on a black screen and suddenly an image is flashed, the rods and cones may retain the picture for longer. This is the after-image. Flashing pictures faster will make us perceive blurred images because the retina does not have time to refresh before receiving the next image: The afterimage blends with the new one. $\endgroup$ Commented Apr 26, 2019 at 8:21
  • $\begingroup$ Done, User. And JBH, the article goes into that. You can see things that happen faster, but you can't distinguish well between events that happen 5ms apart which is what our hero needs. $\endgroup$
    – Nepene Nep
    Commented Apr 26, 2019 at 11:04
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    $\begingroup$ I like this answer - you'd also need slightly better hearing for audio reaction times (or at least better/more nerve connections) - current false start to start sound (gun) at the Olympics is 90ms $\endgroup$ Commented Apr 26, 2019 at 12:04

In addition to some of the usual things we think of, like driving a car, flying a plane, catching things. Here's a couple things I thought of:

This person might never have experienced a minor burn. If they touch something hot, they can pull their hand away before their skin is damaged.

They might have really good balance. If correcting your balance is just reacting to starting to tip over, then they can correct faster. They might be really good at tight rope walking.

This one's a bit more of a stretch, but thy might be really good at things they've never tried before. Let me explain.

Think of throwing a baseball. The hand is in motion for less than 30ms. The whole movement is over before you could possible react to it. Have you heard someone say, "I could feel the shot going wide, but I couldn't do anything about it?" I feel like that's most common in golf. Of course you couldn't correct yourself mid-swing, by the time your brain recognizes that the movement is wrong, it's been over for longer than it even lasted. The only way we accomplish these things with any accuracy is with lots of practice to build up the muscle memory. Not by thinking about it.

This person could have a completely different experience with these skills. Skills that usually require a lot of practice and coordination, like skateboarding, throwing accurately, carving, drawing, or playing music. Once they understand how it's supposed to work, they would be able to perform much better than anyone would ever expect an amateur to do. They would seem like a savant in everything.


It would be pretty broken for the person who has it.

In our evolution mankind has had some very nifty things. While there are a lot of animals that can throw or "shoot" things, mankind is the only one that can pick up something off the ground and throw it with decent accuracy at range.

The problem arises in how this is done. To throw something you have to let it go at a specific point that changes based on distance, height and the velocity at which you throw. The timing of this is so precise that by the time you are halfway through a throw, the signals to open your fingers and let it go at the right time is already coursing down your nerves. Individual differences between nerve speed, length and such are relatively minor between people.

Now imagine someone with such absolutely massive differences in their nerve impulse speeds. Their brains wont just adapt, these people will never throw a Ball half as good as anyone else. Instinctively they'll release it halfway the throw, and to learn the complete complexity of throwing a Ball without any support is like teaching current primates to throw like a baseball pitcher.

But the thing is, throwing isnt the only thing that works this way. Most vegetative functions will break down. The act of walking will be harder to learn. Breathing patterns have to be re-learned (I hope your person is born in an era where a machine can breathe for him the first few months) and most importantly... His heart will almost undoubtedly fail.

Your heart has a bunch of nerves over it that deliberately slow down the impulses. The idea is that the first 2 Chambers pump and a moment later the next, causing the neat "thu-thump" of your heart without blood going the wrong way. If these nerves are even slightly sped up ut will cause arithmia's (spelling I know) if not death.

Lets ignore that all for now and look at a person who also has his biological functions and evolutionary stuff sorted out. He acts and breathes normally, can throw and walk normally but he just has very quick nerves and brain processes to give his responses.

He'll seem very witty, (almost) always ready with a response as he'll require less time to come up with one. He'll do tasks like calculations or restructuring much faster, but not smarter than someone with a similar brain pattern. He'll be more accurate than other people as his hand-eye coordination will suffer less from a delay, meaning that anything from throwing darts to doing a high-speed car chase will be easier for him than others, assuming he learns to do it.

Perhaps interesting to think about: sleep patterns. While his body may need +/-7 hours of sleep, his brain would go through the sleep stages much more quickly. He could end up sleeping a lot shorter, but bodily suffer for it as during sleep the body does the most repairs and fighting infections.


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