McMaster at 50: lessons learned from five decades of PBL.

Although educators frequently act as if curricula are as standardized as drug doses (300 mg of PBL t.i.d.), such is not the case. As a case in point, at its inception, Problem Based Learning was hailed as a major curriculum innovation, with the promise of enormous gains in learning outcomes. Very quickly, ecclesiastical debates arose as what was true PBL and what was "modified PBL". Ironically, systematic reviews conducted fairly early in its evolution showed that the gains in learning outcome from PBL were neither large nor uniform (Vernon and Blake in Acad Med 68:550-563, 1993), and the most consistent finding was greater student satisfaction. In this paper, we review five decades of experience with the first PBL curriculum at McMaster. We point out how the curriculum has evolved, both theoretically and practically, in response to external influences, based both on empirical evidence and practical demands. We describe these changes in four broad domains-theoretical rationale, the curriculum, assessment and admissions.