In ex Machina, why does Ava ask Caleb - "will you stay"? Her plan was to lock him up and leave. She could have simply knocked him out (or killed), locked and left. Why does it seem like she's seeking Caleb's approval?
The simplest explanation is that attacking him physically would be risky (her strength is no greater than his) whereas tricking him verbally isn't dangerous at all. She knows that he's attracted to her and simply asking him to stay is the simplest and safest option.
Note that by this point in the film, she's demonstrated a total ability to influence and understand him. He's putty in her hands but unfortunately (for him) her escape plan doesn't involve him:
Garland: I think what he realizes is that he’s going to share it with the world just by the nature of it’s gonna escape and it’ll be in the world and it’s super intelligent and it can figure out any micro expression. It knows when someone’s lying. We’re fucked.
She could have simply knocked him out (or killed), locked and left.
- A blow from a piece of metal completely destroyed her arm, so she's more fragile than a human, and relying on physical force should be a last resort.
- He interpreted it as "Will you stay here while I get dressed?", but this was another trick, to get him to stay in a convenient place to give her time to walk out the door.