What would happen if Devil Fruit that Chopper ate were eaten by a human being?
Most likely nothing would happen, that person would lose the ability to swim but would not gain anything by the fruit itself. This was also answered by Oda in one of the sbs questions.


  
    D: WHAT HAPPENS IF A PERSON EATS A HITO HITO NO MI?[6]
  
  
  O: I suppose I should say they "BECOME HUMAN". Uh, I guess you could
  say that means like becoming an adult, or finding your true spirit or
  something. So basically, people will live more human-like. Well. I
  guess you could say that. Or not. Basically, not. Goodbye. (runs
  away).


http://onepiece.wikia.com/wiki/SBS_Volume_20

EDIT: maybe, the only thing a human would gain is the ability to ascend("to get to a higher state of consciousness") so one would be happy with himself, so to say. However this is just a speculation, and my take on it if something like that would happen and Oda would come up with a "power up" for the user