The debate over the propriety of cognitive enhancement evokes both enthusiasm and worry. To gain further insight into the reasons that people may have for endorsing or eschewing pharmacological enhancement, we used empirical tools to explore public attitudes towards PE of twelve cognitive, affective, and social domains. Participants from Canada and the United States were recruited using Mechanical Turk and were randomly assigned to read one vignette that described an individual who uses a pill to enhance a single domain. After (...) reading the vignette, participants were asked how comfortable they were with the individual using the enhancement. People were significantly more comfortable when they read about enhancement of certain CAS domains than others. We found a modest negative correlation between comfort level and the degree to which the PE was perceived as changing core features of the person. We also found a modest correlation between comfort level and the degree to which the PE was perceived as improving success in life. Finally, using a sequential mixed method technique, we found that participants who felt uncomfortable about PE use overwhelmingly focused on a lack of need and, to a lesser degree, expressed concerns about safety; those who felt comfortable about PE use most frequently mentioned the safety of the pill and its ability to provide a positive outcome. The data provide novel insights into public enthusiasms and concerns over the use of PE. (shrink)