" If they’re not practicing deliberately, even experts can see their skills backslide. Ericsson shared with me an incredible example of this. Even though you might be inclined to trust the advice of a silver-haired doctor over one fresh out of medical school, it’s been found that in a few fields of medicine, doctors’ skills don’t improve the longer they’ve been practicing. The diagnostic accuracy of professional mammographers, for example, doesn’t get more accurate over the years. Why would that be? For most mammographers, practicing medicine is not deliberate practice, according to Ericsson. It’s more like putting into a tin cup than working with a coach. That’s because mammographers usually only find out if they missed a tumor months or years later, if at all, at which point they’ve probably forgotten the details of the case and can no longer learn from their successes and mistakes. One field of medicine in which this is definitively not the case is surgery. Unlike mammographers, surgeons tend to get better with time. What makes surgeons different from mammographers, according to Ericsson, is that the outcome of most surgeries is usually immediately apparent—the patient either gets better or doesn’t—which means that surgeons are constantly receiving feedback on their performance. They’re always learning what works and what doesn’t, always getting better. This finding leads to a practical application of expertise theory: Ericsson suggests that mammographers regularly be asked to evaluate old cases for which the outcome is already known. That way they can get immediate feedback on their performance. "
― Joshua Foer , Moonwalking with Einstein: The Art and Science of Remembering Everything