Medical education aims to train students to become safe and effective clinical practitioners. This includes the ability to make safe and effective clinical judgements and decisions (GMC 2009). It is assumed that trainee doctors acquire these skills through the hidden curriculum. This is not necessarily the case. There is reason to believe that medical education should include some explicit training for doctors to improve their clinical judgements and decisions. This is known as training in clinical reasoning. This thesis explored how to enhance doctors' clinical reasoning through effective training. The aims were to develop and evaluate an intervention informed by decision theory to Improve doctors' reasoning about clinical judgements and decisions. A series of empirical studies were conducted to achieve these aims. A systematic review and questionnaire study were conducted to evaluate existing interventions that aimed to enhance doctors' clinical reasoning skills. There was little agreement between medical educators on how to effectively enhance doctors' clinical reasoning through training. However, the minority of interventions that aimed to improve doctors' awareness about their own reasoning processes were effective. Little is known about how to improve the processes doctors use to make clinical judgements and decisions in practice. A qualitative interview study was conducted to explore doctors' views and experiences of how to make effective clinical judgements and decisions. Doctors had limited explicit insight into their own reasoning processes, such as the methods that lead to good decisions and factors that bias their reasoning. A quasi-experimental. study was developed to evaluate the feasibility of an intervention to enhance doctors' understanding about their own reasoning processes. A brief tutorial was shown that explained the basic science underpinning human judgement and decision making. Doctors were receptive to learning about this information. They found it relevant to their clinical practice and gained knowledge about decision sciences concepts. Findings from this thesis suggest that, potentially, doctors can improve their clinical judgements and decisions through training to understand how they think about clinical problems
