Another inherent limitation to the

Another inherent limitation to the closed vocabulary approach is that it relies upon a preconceived, fixed set of words. Such a study might be able to confirm that depressed people do indeed use expected words (like “sad”) more frequently but cannot generate new insights (that they talk less about sports or social activities than happy people, for example.)

Past psychological language studies have necessarily relied on closed vocabulary approaches as their small sample sizes made open approaches impractical. The emergence of massive language datasets afforded by social media now allows for qualitatively different analyses.

“Most words occur rarely — any sample of writing, including Facebook status updates, only contains a small portion of the average vocabulary,” Schwartz said. “This means that, for all but the most common words, you need writing samples from many people in order to make connections with psychological traits. Traditional studies have found interesting connections with pre-chosen categories of words such as ‘positive emotion’ or ‘function words.’ However, the billions of word instances available in social media allow us to find patterns at a much richer level.”