‘To believe your own thought, to believe that what is true for you in your private heart is true for all men, — that is genius.’ –R. W. Emerson
For example, people who are induced to nod their heads while listening to a message (ostensibly to test the headphones they are wearing for comfort and staying-power) express greater confidence in the message thereafter than those who have been induced to shake their heads while listening. This is just what we would think when observing other people: if they nod while they listen we assume they agree, and if they shake their heads while they listen we assume they disagree. Likewise, right-handed people who are induced to write statements with their left hands express lower confidence afterwards in the statements that they have written than people who write with their right hands. This is because the shaky writing makes the thoughts look hesitant. (And people who look at the written statements of others will make just the same judgments about the writers’ states of confidence.)
People are completely unaware that they are always interpreting themselves in just the same way that they interpret others.