All eligible students received an e-mail during their freshman year inviting them to participate in the project. The e-mail contained a link that took them to an online survey that asked questions about their personality and behavior, as well as their family, friends, and experiences growing up. Upon completion of the survey, students received $10 compensation. Participants also had the opportunity to give a DNA sample and receive another $10. Those who participate in Spit for Science are invited to complete follow-up surveys each year, for which they also receive compensation. All data that we collect is kept completely confidential.