Rapid blinking while listening can mean a couple of things, its a stress signal or can be perceived as agreement or wellbeing with what someone else is saying…When I am listening to someone intently and I am NOT in agreement with them I blink fast and purse my mouth to the side especially when I know they are bullshitting or completely flat out wrong, its my way of being patient and letting get their stuff out and I respond accordingly, I also blink fast when I am pressured or very focused on something so I am leaning more towards stress related….