Compare physical and psychological "addiction"

A physical addiction such as (sorry for harsh topics, I cannot think of other examples) cutting one's arm because they like the way it feels so they do it over, and over, and over again. A psychological addiction is like drinking or smoking, some people like how those things play with their mind and body making it feel a certain way, then they want to get more and more of it, it becomes an addiction that the brain wants, I am not exactly sure if this will help, I hope it does though. Sorry for long response

Explanation:

answer; 4% i believe this is correct;

which of what? i am confused