Participants will be presented with a scenario and questions assessing third-party attitudes towards sibling incest, controlling for ideological attitudes towards sex, crime and punishment (Fessler & Navarrete, 2004). The disgust questions originally used in Fessler and Navarrete (2004) are not included; Question 5 in Part 1 of the incest-related questionnaire was added by us. Order of incest-related questionnaire and questionnaire on general attitudes will be randomized. ---- ### Incest-related questionnaire Participants will be presented with a two-part scenario. **Part 1** Please read the following story and answer the questions below. Carl and Ann are brother and sister. Carl is 26 and Ann is 24. When they were kids, Carl and Ann often played together for hours. After high school, Carl attended college in another city. After he graduated, Carl got a job and rented an apartment. Ann went to college in the same city where Carl lived. In her last year in college, in order to save money Ann moved into Carl’s apartment. Carl and Ann discovered that they were very attracted to each other. At first they would just sit on the couch watching TV together, but then they began kissing. After several months, they started having sex, which they both enjoyed. After Ann graduated, they decided to stay together, living as a couple. They moved to a new apartment and told their neighbours that they were married, hiding the fact that they were brother and sister. Their neighbours often saw them kissing passionately in the elevator, and sometimes heard them making love at night. One day, a neighbor who was visiting looked in Carl's high school yearbook and discovered that Carl and Ann were brother and sister. Soon, everybody in the apartment building knew the true nature of their relationship. [*Rating scale*: 0 = It would not bother me at all all; 10 = It would upset me very much] 1. How would you feel about living in the apartment next door to Carl and Ann? 2. How would you feel about riding in the apartment elevator with Carl and Ann? 3. How would you feel about working in the same office as Carl and Ann? 4. How would you feel about socializing with Carl and Ann? 5. How disgusted do you feel by Carl and Ann's behaviour? **Part 2** In the state where Carl and Ann live, consensual sibling incest is illegal - it is a crime for consenting adult siblings (brother and sister) to engage in vaginal intercourse, anal intercourse, or oral or manual stimulation of each other's genitals. One day, one of their neighbours called the police, and Carl and Ann were arrested. The prosecutor asked the public to submit recommendations for the appropriate punishment for Carl and Ann. Please specify as precisely as possible: the prison sentence (in years and/or months and/or days) which you think is most appropriate for this act: [*open text field*] the fine (in pounds) which you think is most appropriate for this act: [*open text field*] ### Attitudes towards sex, crime and punishment For each of the following statements, please indicate the number that best describes how you feel: [*Rating scale*: 0 = Strongly disagree to 10 = Strongly agree] Reverse-coded items are indicated with [REV]. 1. To reduce crime, we should have more drug rehabilitation, counseling and job training. [REV] 2. Sex before marriage is immoral. 3. The government should regulate the amount of sex and violence allowed on television. 4. Longer jail sentences and higher fines decrease the crime rate - let's throw the book at criminals. 5. Actions, such as drug use and prostitution, that do not harm anyone other than the actor should not be illegal - adults should be able to do whatever they want as long as it doesn't hurt other people. [REV] ### References Fessler, D.M.T. & Navarrete, C.D. (2004). Third-party attitudes toward sibling incest: Evidence for Westermarck’s Hypotheses. *Evolution and Human Behavior, 25*(5), 277-294.