In one chapter, Pennebaker notes that Rudolph Giuliani demonstrated a dramatic increase in I-words during the late spring of 2000, when he was still mayor of New York. Pennebaker fills us in that "Giuliani's life [was] turned upside down. … He was diagnosed with prostate cancer, withdrew from the senate race against Hillary Clinton, separated from his wife on national television … and, a few days later, acknowledged his 'special friendship' with Judith Nathan." Pennebaker adds that "by early June, friends, acquaintances, old enemies, and members of the press all noticed that Giuliani seemed more genuine, humble, and warm." So it's reasonable to conclude that Giuliani's ascending I-word usage reflected a "personality switch from cold and distanced to someone who [due to a few significant setbacks] was more warm and immediate."
But we already knew that. If we didn't, where would Pennebaker's method leave us? He argues, at various points, that the following groups use I-words at higher rates:
2. Followers (not leaders)
3. Truth-tellers (not liars)
7. Afraid (but not angry)
The common thread unifying these seemingly random clusters is, roughly, an enhanced focus on personal experience. Sick and depressed people dwell on their conditions and are thus more likely than their healthy counterparts to talk about themselves. Followers, in conversation with leaders, might be after something: "I was wondering if I could have a raise." That's pretty close to a tautology, though, and does nothing to solve the problem that, without insider information, it's impossible to know which condition or attribute I-usage reflects. A word-count-wannabe presented with Giuliani's speeches might deduce, erroneously, that the mayor had become more truthful, or less leaderly, or had lost money.
For obvious reasons, I'm unusually attuned to my pronoun usage at the moment, and I've noticed a thing or two. I start off this essay with lots of we-words (16 in the introduction), and sprinkle them throughout. With the exception of the section you're currently reading, I drop only one self-referencing I (in the fifth paragraph). I don't deny that this imbalance might mean something. Perhaps it indicates that, like politicians who drone on about what "we" expect from the president, or how "we" want a return to old-fashioned American values, I'm trying to imply audience agreement when, in truth, I have no clue what the audience thinks. But you don't need to count pronouns to figure that out. You only need to know that you're reading a book review.