adequately deal with the problem. After a period of self-directed learning, students share what they have learned about the topic and test whether their new understanding of the problem is now more accurate and elaborate than before. Once students are satisfied with their learning outcomes, they engage with a new problem and the cycle starts all over again (Hmelo-Silver 2004; Schmidt 1993).
PBL can be interpreted as a form of cognitive-constructivist learning, based on at least three assumptions (Schmidt et al. 2009). The first assumption is that in PBL students engage in theory construction. With the help of their peers they develop an initial theory about the phenomena described in the problem. Subsequently, self-directed learning activities (e.g. reading books or consulting internet resources) serve to test the initial theory against the literature thereby elaborating and changing and deepening their understanding of the topic. The second assumption is that the use of authentic problems or real-life problems encourage students to become interested in the topic at hand and as a conse- quence helps them gaining a deeper understanding of the principles or processes under- lying the problem. The third assumption is that being in the position to identify one’s own learning goals in collaboration with peers fosters a feeling of autonomy, agency, and empowerment. Being autonomous from the direct intervention of a teacher and feeling in charge of one’s own learning is supposed to result in increased cognitive engagement with the topic to be learned, which eventually encourages deeper understanding of it.
There is some empirical evidence suggesting that what students do in the tutorial group is indeed attempting to construct a mental model or ‘‘theory’’ that explains the phenomena described in the problem. For instance, De Grave et al. (2001) showed students videos of their own contributions to a tutorial discussion and asked them to recall what they were thinking. This stimulated recall procedure in combination with verbatim transcripts of the verbal interaction in the group suggested that indeed theory building, and to a lesser extent, data exploration and hypothesis evaluation were central to the thoughts and verbal utter- ances of the students.