extremely good observation that makes me think that part of the enduring (even growing) awe towards performers like Daniel Day-Lewis and Meryl Streep is their (apparently) effortless ability to do this. Philip Seymour Hoffman was good at it too
it really doesn't seem like actors today learn to pretend how to be someone else. instead, what they learn (& get very good at), is how to display unspoken thoughts on their face (which is not how real people actually behave)