The recruitment of participants for online survey research presents many challenges. In this work, we present four experiments examining how two different kinds of "surprise" financial incentives affect the rate of participation in a longitudinal study when participants are initially solicited with either an appeal to intrinsic motivation to participate in research or one that also offers extrinsic financial incentives. We find that unexpected financial incentives ("existence surprises") presented to people who click a recruitment advertisement focused on intrinsic incentives lead to a lower recruitment rate than do the same incentives offered to those who clicked an advertisement that led them to expect it. However, when potential participants expect a financial incentive, surprising them with a higher amount ("amount surprises") yields a higher recruitment rate. We interpret these results in the context of crowding theory. Neither type of surprise affected ongoing participation, measured as the number of questions and questionnaires completed over the course of the study.

Online dating systems play a prominent role in the social lives of millions of their users, but little research has considered how users perceive one another through their personal profiles. We examined how users perceive attractiveness in online dating profiles, which provide their first exposure to a potential partner. Participants rated whole profiles and profile components on such qualities as how attractive, extraverted, and genuine and trustworthy they appeared. As past research in the psychology of attraction would suggest, the attractiveness and other qualities of the photograph were the strongest predictors of whole profile attractiveness, but they were not alone: the free-text component also played an important role in predicting overall attractiveness. In turn, numerous other qualities predicted the attractiveness ratings of photos and free-text components, albeit in different ways for men and women. The fixed-choice elements of a profile, however, were unrelated to attractiveness. Author Keywords Online personals, attraction, computer-mediated