8
$\begingroup$

In the isekai genre of anime, it is a common trope for a person to be reborn into a baby's body while retaining their full cognitive abilities. Assuming they maintain full control of their coordination (balance and limb control), how long would it take for such a person to develop enough muscle strength to begin walking for a sustained period of at least a few minutes? With regular babies, the largest limiting factor is the amount of time it takes to learn to balance and walk, as far as I am aware.

While it would likely take some time for a person to recalibrate to their new body, for this question you can assume that time to be negligible. I am only asking after the stage of development/age at which their muscle strength would be sufficient.

How such a person would maintain their cognitive abilities while having the underdeveloped brain of a baby is not relevant. You can assume that to be magic.

$\endgroup$
5
  • $\begingroup$ While this is not a duplicate, we have had lots of questions about how quickly superbabies can learn to walk, how strong they need to be etc - I suggest you search on those questions. However, if you are removing balance as a limiting factor and only interested in strength then the real question is "at what age can a baby pull themselves upright", which can be Googled easily. $\endgroup$ Commented Jun 29, 2023 at 22:24
  • $\begingroup$ The barrier to babies walking isn't that they don't know how. Likewise a babies brain presents some problems since babies don't retain and process memories in the same way. What it would mean for the memories and stream of consciousness to already be there depends on the technology. $\endgroup$
    – futurebird
    Commented Jun 30, 2023 at 2:52
  • $\begingroup$ @KerrAvon2055 i looked at those before asking, and didn't feel them to answer my question $\endgroup$
    – M S
    Commented Jun 30, 2023 at 11:36
  • $\begingroup$ @futurebird other than the first sentence, I don't really understand your comment $\endgroup$
    – M S
    Commented Jun 30, 2023 at 11:36
  • $\begingroup$ Our brains change as we learn and age. Somehow this allows us to retain memories and skills. Since no one can remember anything from the first 6 months to 2 years of life, the way that memories form in a new brain may be radically different. It's not that a baby can't remember anything, they clearly can, but these memories don't last. I'm questioning what it would mean to "put" an adult brain into a infant. You could, literally transplant the whole organ-- but it would not even fit. The head expands as we grow up-- how can a smaller structure be the same as a larger one? $\endgroup$
    – futurebird
    Commented Jun 30, 2023 at 12:48

2 Answers 2

8
$\begingroup$

Between 9 and 18 months


Typically, the milestones for normal babies are creeping around 6 months, pulling up to stand around 9, taking steps around 11 and walking around 12 or 13. Much of this learning is instinctual. We don't learn how to creep by reading a book or consciously ruminating on what muscles are involves and what steps might be required to accomplish the task.


You're positing something that is lies within a triangular continuum between a new baby freshly learning to walk (as above), an injured adult relearning to walk, and a normal adult considering the processes of both.


Assuming that these sort of reincarnated old babies are born with the old non-corporeal mind & consciousness properly seated within the physical brain & body, I would argue that this person would have a time advantage. Not much, really. The old baby would be born already self-aware, already pre-loaded with the knowledge of how to walk, already having the self-determination and conscious desire to walk.


This person would only have to wait for the muscles and nerves to sufficiently develop and strengthen. Therefore I'd argue that a person with a strong will and desire to walk as soon as possible and gets the support she'd need would probably be able to walk by nine months after birth. A person with less determination and less support would probably take a little longer.

$\endgroup$
3
$\begingroup$

By the time a baby is 7-8 months old, they've developed sufficient strength to theoretically be able to walk, which is why this is when babies normally start standing on their own.

That said, I don't know if having pre-existing coordination helps. Remember that coordination isn't simply software that's loaded in, it's based on automatic reflexes, practice, and conscious thought developed by a system where the software is an intrinsic part of the hardware that has been in development for however old the person is. Putting aside "magically adapted to the body" exceptions, you've got someone in a body that, prior to meeting Truck-kun's front bumper, is hugely different in proportions, weight distribution, and basic size from what they're in now.

It's well known that children undergoing rapid growth spurts can sometimes be a bit uncoordinated because they're unused to their new proportions. Now imagine that magnitudes worse.

Again, magic aside, I don't think someone would actually have that much of an advantage over a normal baby. They could, given the premise, have an advantage in learned skills; something like playing an instrument, or touch typing, or something, but I suspect they'll have no great advantage, at least not one noticeably greater, when it comes to basic body movements than that of any physically precocious child not inhabited by someone who couldn't look both ways.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .