Muscle memory

So I've changed the number code on my cellphone to unlock the keylock about a week ago. I only changed it a bit actually. I know very well the combination of the new code, because it has more meaning for me now than the old one did. Hence the change. But it took me about four days or so to not type in the old code just out of habit. Four days! Although the new code has more meaning! Four days and repeated false entries.

It's not just habit, which to me seems more a head thing. It's also muscle memory. In my head what I type is numbers as well as letters. I couldn't for the life of me tell you the "pure" numbers of the code, because I have no idea what numbers I'm typing for the letters. I know the letters though and my fingers know which keys to hit.

And for two days or so now I type the new code without failure. Interesting this habit and muscle memory thing.