Cognitive forcing strategies (CFS)may reduce error arising from cognitive biases. This is the first experimental test to determine the effect of CFS training in medical students.

Students were allocated to CFS training or control during a 4-week emergency medicine rotation (n = 191). At the end of the rotation examination, students were tested using computer-based cases. Application of CFS could enable reduction of diagnostic error, as evidenced by identifying multiple correct diagnoses for the two cases prone to search satisficing bias (SSB) and uncommon diagnoses for the two cases prone to availability bias (AB). Two “false positive” cases were included to test for possible “oversearching.”

There were 145 students in the intervention and 46 in the control group. For the SSB cases, 52% of students with CFS training and 48% in the control group initiated a search for the second diagnosis (χ2 = 0.13, df = 1, p = 0.91). More than half (54%) correctly identified the second diagnosis in the CFS group, and 48% identified it in the control group. The difference was not significant (χ2 = 2.25, df = 1, p = 0.13). For the second diagnosis in the false positive cases, 64% of the CFS group and 77% of the control group incorrectly identified it. There were no significant differences between groups (χ2 = 2.38, df = 1, p = 0.12). In the AB cases, only 45% in each group identified the uncommon correct diagnosis (χ2 = 0.001, df = 1, p = 0.98).

The educational interventions suggested by experts in clinical reasoning and employed in our study to teach CFS failed to show any reduction in diagnostic error by novices.