Still thinking about “doing nothing“.
There is a system in Drama Princess that makes the Actors look at Objects. It is not part of any behaviour but just an automatic system that is always active. It makes Actors look at objects in their vicinity, follow a moving actor with their eyes and just randomly look in a non-specific direction once in a while. Perhaps we need more systems like this to allow Actors to “do nothing” in a believable way. Without needing to make a decision about choosing a certain behaviour. Just automatic responses to the environment, or reflexes.
Two things come to mind: proximity and imitation.
The distance between two Actors tells a lot about their relationship. Actors should be able to automatically choose the distance to another Actor that is appropriate for the affection between the two. Also, looking at each other or looking in the same or opposite direction, can be very meaningful. Facing each other or standing side by side.
Actors that remain close to each other for a while probably like each other. When people like each other, they imitate each other’s pose and motions subconsciously. Drama Princess actors could do the same. If one Actor looks at a bird flying by, the other should probably look at that bird too (or at least in the same direction). If one Actor strokes his hair, the other could do that as well. Etc.