In his book, You Are Not So Smart, David McRaney describes an experiment by Elizabeth Newton that explains the illusion of transparency. This happens during the communication process when others are not privy to same information as we are. While we may think all of our thoughts and feelings are visible to others, we often overestimate the actual transfer of information.
The participants pair up and one partner taps out a familiar song with fingertips. The finger-tapping partner predicts the listener will be able to guess the tune. These partners are surprised to discover that while the tune is obvious to them, their listening partner is unable to guess it.