Psychologist James Pennebaker says that “function words” (articles, pronouns, prepositions, auxiliary verbs) are the most-used but least-appreciated parts of speech. Though we focus on content words, function words add important information about personality, emotion, and intent.
Say someone asks “What’s the weather outside?” You could answer “It’s hot” or “I think it’s hot.” The “I think” may seem insignificant, but it’s quite meaningful. It shows you’re more focused on yourself.
Of course, I am more interesting than the weather. (I think.) So that example is a little weak.
But Pennebaker’s next example—of deception by a strategic combination of abstraction and misdirection—is right on target:
A person who’s lying tends to use “we” more or use sentences without a first-person pronoun at all. Instead of saying “I didn’t take your book,” a liar might say “That’s not the kind of thing that anyone with integrity would do.”
See James Pennebaker, Your Use of Pronouns Reveals Your Personality – Harvard Business Review. He also has a book titled The Secret Life of Pronouns.