One of my goals is to understand individual differences using the cues evident in the social environment. One of those cues is language.
Additionally, to complement simple word-counting approaches, Tal Yarkoni and I created a text analytic system called the Contrast Analysis of Semantic Similarity (CASS). You can download it for free at www.casstools.org. We’ve written a couple of papers validating CASS. You can download them here and here.
I am also in the process of collaborating on projects that employ machine learning and topic models to better understand some individual differences (e.g., narcissism).