Does a high average daily caffeine consumption create a tolerance to the effect of caffeine?

Hi,

Participants took part in a reaction time test. They repeated the test 2 times on seperate occasions, once with caffeine (experimental) and once with no caffeine (control).

Each participants average daily caffeine consumption was measured by a self report questionnare.

I am looking to see if the daily caffeine consumption creates a tolerance to caffeine and therefore if this effects performance (reaction time) by comparing the experimental to control

Would i need to test for normality?

What correlation should i run?

Many thanks