However, I found this story, written by Jessica Wapner for the science section of the New York Times, so intriguing I couldn't resist posting a summary.
In short, James W. Pennebaker, a professor of psychology at the University of Texas, has discovered interesting things about people's choice of words in speech. It's called text analysis, and it consists of counting the different kinds of words a person says.
Excessive use of first person pronouns (I, me, mine) indicates insecurity and a sense of being threatened. When you are sick or hurt, you use first person words more often (I want water, please help me). As you get better, you gradually drop this use of egocentric terms. Liars, on the other hand, avoid first person pronouns -- undoubtedly because they want to keep the focus away from themselves -- and use negative words (hurt, ugly, nasty) instead.
There are more fascinating conclusions drawn. Those who are mentally alert are more likely to use causal words (because, since, therefore). Men use more articles (a, the, that, this) while women use more second and third person pronouns (he, she, they), probably because men are more concrete thinkers, and women are more empathetic.
The world of diplomacy and espionage is interested. Dr. Pennebaker has received a grant from the Army Research Institute to study how foreign leaders use language.