A trainee learns a procedure by watching it once, performing it once, and then teaching it to the next trainee.
The maxim is attached to the residency system William Halsted built at Johns Hopkins from the 1890s, which moved surgical training from lectures to graded responsibility on real patients. The phrase itself is later folklore. Its compression of practice into single repetitions has been criticised for decades, and simulation training grew up largely to take the 'do one' off the patient.
In practice
- A hospital lets junior doctors place central lines after watching one, and its complication rate falls only when it adds a mannequin and a checklist before the first real attempt.
- A new barista shown the milk steamer once is training the next starter by the end of the week, and the café's coffee varies accordingly.
- Possible explanations
- The explanation is graded responsibility: the maxim compresses an apprenticeship into three steps, on the assumption that observing, doing and explaining each add something the others cannot.
- In its favour
- The teaching step is the defensible part, since explaining a procedure improves the explainer's grasp of it, and the residency system it came from was a real improvement on lecture-based training.
- Against it
- Single repetitions are far short of what skill acquisition requires, patient-safety research documents the cost of learning on real patients, and simulation grew up largely to take the doing step off the patient.
- Standing
- Criticised on patient-safety grounds and against the evidence that skill needs repeated practice with feedback. The teaching step is the defensible part. Compare deliberate practice and docendo discimus.
- Subject
- Learning & Education
- Essay
- Theories of teaching, and what schools are for