A team of UCLA scientists recently published a study in Nature Neuroscience indicating that the hippocampus (at least in rats) reacts differently to virtual environments than to real ones. (If — like me — you are not a neuroscientist, you may prefer this news article to the paper.) The hippocampus is a region of the brain heavily involved in forming memories, and in creating spacial maps.
In short, the researchers found that a specific type of neural activity that is present when rats explore a physical space is completely absent when the rats are given a purely visual immersive simulation to explore. The behavior is more or less normal in both environments, and memories are created, but some part of the process of creating a physical spatial model seems to be missing.
We are a long way from drawing conclusions about specific advantages or disadvantages related to humans performing learning or other tasks, but this research is a reminder that we still have a lot to learn about how we learn. It will be important for us as computer researchers not to make assumptions about what VR can and cannot do.