Worked examples for teaching electrocardiogram interpretation: Salient or discriminatory features?

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Cognitive load theory states that one way to optimise learning is to decrease extraneous cognitive load, defined as information not relevant to task completion. Worked examples, which show the learner the logic behind the solving of a problem, can decrease extraneous load. However, there is little research to guide the optimal formatting of worked examples. In a crossover design, first-year medical students were randomised to worked examples of bradycardias with salient features first and tachycardias with discriminatory features second (n=33) or worked examples of bradycardias with discriminatory features first and tachycardias with salient features second (n=32). After each learning phase, participants completed a testing phase. Diagnostic accuracy and reported cognitive load were compared between the two worked example formats, as well as with data for a group of historical controls, consisting of medical students interpreting electrocardiogram rhythms without worked examples. Each module concluded with a questionnaire in which the learner was asked to rate his or her perceptions of the difficulty of the core content, the clarity with which the information was presented, and perceived learning. Worked examples highlighting salient and discriminatory features were associated with similar levels of diagnostic accuracy (56% and 60%, respectively; P=.32). Both worked example conditions were associated with higher diagnostic accuracy than was found in historical controls (P<.0001). There was no difference in the extraneous load experienced between worked examples highlighting salient features and those highlighting discriminatory features (12.5±6.1 and 11.9±6.1, respectively; P=.52). Participants reported greater intrinsic load in the worked examples highlighting salient rather than discriminatory features (17.1±4.9 and 15.5±4.6, respectively; P=.01). Discriminatory feature-based worked examples were associated with less intrinsic cognitive load, but this did not translate into any meaningful difference in diagnostic performance. Instruction with worked examples improved diagnostic performance regardless of whether salient or discriminatory features were highlighted.