The gestures and speech in a performance come at the end of a lot of verbal preparation. Lots of writing, note taking, talking and, if you're me, listening back to recordings of talking. Some alchemical process takes place during preparation that helps one transform psychology into behavior.
It's a lot easier to witness during playback. I try to be as attentive a director as I can, but while going back over the footage I inevitably notice remarkable details the actors are giving that demonstrate their intimacy with the character. Sometimes it's a comment or a reaction they have. I notice it less in myself, in part because I may be over-intellectualizing my performance. It's not a surprise, since I'm also the writer and director, but it's something I want desperately to improve.
Of course, when I assigned myself a role in Delta Phi, I was actually doing it in part because I was curious about what that kind of over-intellectualization and self-consciousness could do for the role. But how to turn psychology into behavior...I'm assuming it's subconscious. Like turning dialogue into motivation: when writing, I prioritize observing my characters as opposed to analyzing them. It's usually only after a lot of writing that I can actually decode what their motivations are. If I use that as a model, it would follow that I must do more acting. Thus far we've been using most of the rehearsals to discuss things behind the script rather than practice lines. Part of that is because the script for Delta Phi has a lot of context and we had to start production right behind the script's completion. I'm eager to switch over to more practicing. The timing hasn't felt ideal, but it's usually these kind of high-impact, condensed experiences with a craft that allow for the most learning.