Conclusion
In the past 20 years, we have learned a great deal about how college students learn a large number of specific topics in physics — at least in some classes.
Most research in college level physics learning has focused on concept building and observation.
In the next few years, we will need to understand the role of expectations and attitudes in student learning and to begin to build a coherent model that helps us make sense of what we see and develop teaching methods that “work”.