Table 1.

Research question 1 (RQ1) about design approaches, type of study, and outcomes.

Authors	Goals	Keywords	Type of Study	Main Outcomes
Green, MacDorman, and Vasudevan (2008) [16]	To measure human responses to varying facial proportions in people, androids, mechanical-looking robots, and two/three-dimensional characters	Anthropomorphism, attractiveness perception, facial acceptability, interrater agreement, uncanny valley	Survey study	Significant correlations were made between the selection of best proportions and ratings of human likeness and attractiveness.
Norton et al. (1996) [17]	To compare actual proportions of adults’ body shape with dolls (Barbie and Ken)	Social psychology, body shape	Anthropometric study	Unrealistic body proportions of Barbie and Ken were compared to real humans.
Szczuka et al. (2017) [18]	To compare men’s sexual attractiveness of sex robots and women	Sex robot, personality traits, attractiveness, HRI	Survey study	A negative attitude towards robots is the main user characteristic that predicts the attractiveness ratings of sex robots.
Rousi (2018) [19]	To problematize human–robot love and sex relationships	Emotions, robots, sex, infidelity, artificial intelligence	Review essay	Human–robot love and sex relationships are problematized in the eventuality of artificial emotions.
Hou and Ye (2019) [20]	To test out sex differences in preferences for male and female faces and voices	Sex differences facial attractiveness, vocal attractiveness, mate preferences	Computerized test	Men preferred voice recordings and multimodal stimuli of women. Women did not show different attractiveness ratings for the voices of men vs. women.