This questionnaires measures the participant's belief that their co-participant is phenotypically similar to themselves. Questions 1-12 are taken from the Physical Similarity Scale from Bressan, Colarelli and Cavalieri (2009). Scores on items 1-12 will be summed together to obtain a self-similarity score. ---- ### Physical Similarity Questionnaire Please answer the following questions on how similar you think you look to your co-participant. [*Rating scale*: 1 = Hardly at all to 5 = Extremely much] 1. How much do you and your co-participant look alike overall? 2. How often have people told you that you and your co-participant look alike? 3. How similar in height are you and your co-participant? 4. How similar in weight are you and this sibling? 5. How similar in body structure are you and your co-participant? 6. How similar in facial features are you and your co-participant, in general? 7. How similar are you and your co-participant in facial coloring? 8. How similar are you and your co-participant in eye coloring? 9. How similar is your and your co-participant’s smile? 10. How similar are your and your co-participant’s noses? 11. How similar are your and your co-participant’s lips? 12. How similar are your and your co-participant’s cheekbones? 13. Who in your family (other than you) does your co-participant most look like? [*Drop-down*] - Your sibling - Your parent - Your child - Your grand-parent - Your cousin - Your aunt/uncle 14. What is this family member's gender? [*Drop-down*] - Male - Female 15. This family member is a ____ relative. [*Drop-down*] - biological - step - in-law - adopted 16. Through which side of your family are you related to this family member? [*Drop-down*] - Your mother's side - Your father's side - Both (sibling) 17. How much do your co-participant and that family member look alike overall? [*Rating scale*: 1 = Hardly at all to 5 = Extremely much] ---- ### References Bressan, P., Colarelli, S. M., & Cavalieri, M. B. (2009). Biologically costly altruism depends on emotional closeness among step but not half or full siblings. *Evolutionary Psychology, 7*, 118-132.