5 years from now I plan to be done with college. Aside from that, I'm not really sure what I plan to be doing with my life. But when I look back at what I remembered from college there are a few things that I am almost certain I will still remember. One of these things is the concept of classical conditioning.
In my mind this is one of the most basic fundamental concepts of psychology, but also one of the most interesting. It can be used to train animals for anything from lifesaving purposes to childish entertainment. It also shows some of the more basic functions that go on in the human mind, giving us a more simple idea that we can completely grasp as opposed to some of the more complicated things that are not yet entirely understood.
In addition to the concept itself, the way it developed was a good example of how many scientific discoveries arise. Through testing of theories, a few accidents that expand on the knowledge and lots of research.
Between it being a basic fundamental idea of psychology, as well as something I could perhaps attempt someday, I doubt that 5 years from now I will forget what classical conditioning is.