In particular, as one ages they think less about the immediate present and more about the future (Friedman, 2000;Nurmi, 2005;Steinberg et al., 2009), and females tend to think a bit more about the future than males (Keough et al., 1999).
features 3 available here: wwbp.org/public data/happierfuntokenizing.zip are encoded simply as binary indicators for whether the ngram appears in the message.