Problem-Based Learning is an intriguing, if not proven, method of facilitating learning. A new journal has been launched to gather research related to problem-based learning. The first issue is available free online.
In that first issue, John R. Savery provides a nice overview of Problem-Based Learning (PBL). In it he acknowledges that the research has not shown that PBL is more effective than traditional learning approaches.
In thinking about PBL, please keep in mind that, like many learning approaches, PBL is really a compendium of many separate learning factors (for example, problems should be ill-structured, collaboration is essential, etc.). It could be that many of the components have value, but one or another of PBL’s components may actually suppress learning. As Savery notes, more research is needed.