He doesn't even glance at him? He doesn't even start to glance at him? It's practically an automatic reflex to do it.
Detection of motion is what "far peripheral vision" is all about. Here's a paper about it from the Army. It says that for far peripheral vision which goes to 170 degrees: "Motion detection is only modestly diminished compared to that of the fovea."
"In general, motion detection has been reported to be a robust attribute of peripheral visual function, revealing fairly consistent threshold responses for a variety of different conditions.".