system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how muscle memory works.

I find it fascinating that our fingers can type out words without a keyboard. [5]
gpt
When you perform a sequence of one or more actions your brain will begin to associate those actions with each other. There's a saying that goes "Neurons that fire together wire together", which can be interpreted in this context to mean that if you perform two (or more) actions in sequence often enough, the motor neurons responsible for the sequence of actions will become directly connected. Performing the first action will excite the neurons responsible for the second action and make them more likely to 'fire', those excite the neurons responsible for the third action, etc.. Each time you complete this sequence of actions the association between all the neurons involved in completing that sequence grows stronger. Essentially your brain has to work less hard each time you complete that sequence of actions, playing a scale on an instrument for example. This applies for all neurons though, not just motor neurons. Pretty much, if anything reminds you of anything else it is a product of this phenomenon. Your brain associates things when they occur simultaneously or sequentially.