The role of the teacher differs dramatically in a PBL class from that of the traditional classroom, where the teacher determines the content and sequence of the objectives to be met, and provides direct instruction. Teachers most often function as metacognitive coaches, asking students how they know what they know, and getting them to examine their thinking. Four Common Elements Ill-structured problems. The characteristic that is probably most central to PBL is the use of problems that are ill-structured. Problems that students typically are expected to solve in school are well-structured.
Students know exactly what the problem is, and know when they have gotten the right answer.
The importance of using ill-structured problems lies in the type of thinking in which learners engage while working with these problems. Typically, only one solution is correct, and the learner practices the plan until it becomes automatic. The thinking involved is reproductive, because the learner simply reproduces known procedures in a static fashion. In contrast, when a problem is clearly presented but a plan of action is not, the learner cannot rely solely on the retrieval of previously learned information, and instead must use reason and analysis to produce a plan of action and arrive at a solution. The need for creative insight is at the heart of productive thinking.