if you did a "semester's worth of research" but still highlight on that throughout your app..then it looks pretty crappy imo. However, if you "quit" after a semester worth of research realizing it's not for you..then I'm sure it's not a big deal. research is not for everyone..so don't make your life miserable if it's not your "thing"...(but def. give it a try if you have some interests!)
med schools wanna see commitment, dedication and passion..doing a semester's worth of anything doesn't quite show that imo