Abstract Social interface theory has had widespread influence within the field of human–computer interaction. The basic thesis is that humanizing cues in a computer interface can engender responses from users similar to those produced by interactions between humans. These humanizing cues often confer human characteristics on the interface (such as gender) or suggest that the interface is an agent actively interacting with the respondent. In contrast, the survey interviewing literature suggests that computer administration of surveys on highly sensitive topics reduces or eliminates social desirability effects, even when such humanizing features as recorded human voices are used. In attempting to reconcile these apparently contradictory findings, we varied features of the interface in two Web surveys and a telephone survey. In the first Web experiment, we presented an image of (1) a male researcher, (2) a female researcher, or (3) the study logo at several points throughout the questionnaire. This experiment also varied the extent of personal feedback provided to the respondent. The second Web study compared three versions of the survey: (1) One that included a photograph of a female researcher and text messages from her; (2) another version that included only the text messages; and (3) a final version that included neither the picture nor the personalizing messages. Finally, we carried out a telephone study using a method—interactive voice response (IVR)—in which the computer plays a recording of the questions over the telephone and respondents indicate their answers by pressing keys on the telephone handset. The IVR study varied the voice that administered the questions. All three surveys used questionnaires that included sensitive questions about sexual behavior and illicit drug use and questions on gender-related attitudes. We find limited support for the social interface hypothesis. There are consistent, though small, effects of the “gender” of the interface on reported gender attitudes, but few effects on socially desirable responding. We propose several possible reasons for the contradictory evidence on social interfaces.