摘要：This article introduces the Conditional E-mail Response Technique (CERT) as a systematic, hidden observation technique to measure behavioral tendencies. Although CERT derives from older techniques such as lost-letter/lost-e-mail techniques, we show how CERT is unique: each participant receives several e-mails with varying content, allowing the researcher to observe response rates and valence as a function of the manipulated content. Our study investigated discrimination against foreigners in the apartment rental market in Heidelberg (a German university city) by recording lessors' (non-) responses to 600 e-mails from fake applicants. Each owner (N = 120) received five applications for a one-room apartment via e-mail. Applicants' ethnic identities were communicated through their names. The results showed a remarkable bias against foreign names compared to German names. The response rates for foreign applicants were almost half that for German applicants (response rates were 78% for German names compared to 44-54% for American, Italian, Russian, and Turkish names). The relative risk of a rejecting response was up to eight times higher for e-mails appearing to come from foreigners. Applicants with foreign names were noticeably more likely to receive either no response or a negative response, that is, to have a negative outcome. There were also differences among the foreign applicant groups. We discuss the implications, ethical considerations, and advantages of CERT compared to other related techniques, as well as possible future uses.
