I never thought about it before, but with me the psychology comes first. I'm not good with outlines. I just get a feeling I want to convey. I come up with a simple plot. Then I think of a few characters (usually a protagonist pops up quickly). Then I write for that feeling. Every few scenes I try to up the ante. Subplots and character arcs seem to follow.

I need to have the basic turnpoints set, but if that is called pshychology I don't know. I try to figure out how the character thinks and do as much prework as possible. But it is when I write that the characters come alive. But without the prework they wouldn't do that.