People spend a lot of time on the internet: we interact with other people, write on blogs, buy products, and search for websites. These seemingly everyday interactions create a large-scale, naturalistic record of human psychology. I test psychological hypotheses in this natural laboratory using computational techniques from machine learning and natural language processing. I have applied these methods to study decision-making (Thorstad & Wolff, 2018a), mental illness (Thorstad & Wolff, 2018b), and how people think about the future (Thorstad & Wolff, in prep.).