Neuroscience
There are surprises everywhere in this field. The mystery of how brain works will remain unsolved for at least another century, I think. Just when the theories look fine, usually an unexpected result shows up and changes everything. You never know what the brain has in store for you.
A lot of the past work related to brain was done by studying trained animals as subjects. But now brain plasticity has raised a big concern. The researchers then turn to untrained animals, and the same task can not be repeated for too many times since that would be considered training....this is getting interesting. A lot of past papers need to be checked again for wordings.
It's now too late for me to switch my major, but if I had taken some neuroscience course back when I was a freshman, my life would probably be completely different. Well, I don't really like the idea of sticking an electrode into an animal though. Poor monkeys. It's fine to read the papers, though I will give a second thought before I actually did that myself.