Responsiveness means "being able to react quickly," like a sports car whose responsiveness makes it fun to drive, or a "responding with emotion," like the responsiveness of an audience at the concert of their all-time favorite singer.
Have you ever wondered if your friends were even listening while you poured your heart out? Think about their responsiveness, or how focused they were on your feelings and their own. Did their eyes well up when you started to cry? Or did they stare into space, waiting until you were finished so that they could talk? Responsiveness is a characteristic that shows how much someone cares.