Answer:
Based on my own understanding, the image tells that a person who usually does a lot of talking is often the one who actually knows nothing. While someone who prefers to be silent is mostly the one who thinks first before speaking. It seems to me that the one who's talking is not really making any sense; unlike the other one who seems to have broader understanding and does not immediately resort into telling things that aren't worth telling.
But there can also be other interpretations of the picture. What I answered above is merely from the way I understand the image.
