Field notes: Seeing is believing.

An ultrasound of the calf. Getty Images/Henadzi Pechan

There’s an aphorism taught to medical students that goes like this: “Listen to the patient. He is telling you the diagnosis.”

The obvious intended message is the apparent profundity found within simplicity. Ignore the newly acquired ocean of knowledge swimming around in your brain, the master says to the apprentice. Instead, do something far more basic and humanistic: really hear your patients.

It sounds so easy. It isn’t—and for several reasons. A few years ago, a then-new piece of technology made me acknowledge just how often we don’t do this.