So explained my Clinical Skills mentor after one of my classmates finished interviewing her standardized patient. SPs - actors paid to present with a particular history and illness meant for us to uncover - are the wading pool in which we dip our toes before interviewing (and yes, examining) real, honest-to-goodness patients in just a few short weeks.
When I worked in the ER, I had few problems establishing a good rapport and asking questions of my patients. SPs are a little different. Maybe the video camera and 12 other people watching the interview have something to do with it, but more likely is the fact that we're asking questions and obtaining information without any idea how to act on it. I know that will come in time, but for the moment it feels like we're acting just as much, if not more, than the SPs.
I suppose you could say that we're learning the importance of projecting confidence, of affecting the right demeanor with open body language and maintaining eye contact.
Put another way, the motto could be "fake it 'til you make it."