Why do reaction times(reflexes) differ from person to person?

Wny does your reaction time improve when the same thing is done over and over again. ( slap in face 10 times)

2 answers

because no two people are alike. even twins who look the same are different. everyone moves/reacts at their own level/speed and some are faster than others.

as for the second one. if i slapped you in the face 10 times don't you think you might move out of the way? its called practice makes perfect, or slap me again and ima kick u in da face.
As acts are repeated, the neural connections related to those responses become stronger, leading to quicker reactions. Previous experiences effect this neural development, which changes reaction times.

After the second slap, I probably would do more than move out of the way. Depending on the relationship and situation with the other person, I would restrain that person and ask for an explanation or possibly return the favor.

I hope this helps a little more. Thanks for asking.