how sweet chocolate can be for our mind??

As a nurse, I took board examinations before I can finally work. When I was reviewing for my exams (yes, exams...passed 3 licensure exams already..wink***), I often eat chocolates because I heard it is good for those take taker. I didn't really know the explanation to it...but I guess it works :-) So yeah...I prefer chocolates on both: when having an exam and when thinking!