Relationships of physical resemblance to personality similarity and social affiliation have generated considerable discussion among behavioral science researchers. A “twin-like” experimental design (involving genetically unrelated look-alikes, U-LAs) explores associations among resemblance in appearance, the Big Five personality traits, self-esteem, and social attraction within an evolutionary framework. The Personality for Professionals Inventory (PfPI), NEO/NEO-FFI-3, Rosenberg Self-Esteem Scale, and a Social Relationship Survey were variously completed by 45 U-LA pairs, identified from the “I’m Not a Look-Alike” project, Mentorn Media, and personal referrals. The mean U-LA intraclass correlations were negligible for all Big Five personality traits on the PfPI and NEO/NEO-FFI-3 (ri = −.02 and − .04, respectively). In contrast, mean ri values of .53 and .15 for monozygotic (MZA) and dizygotic (DZA) reared-apart twins, respectively, have been reported for these personality measures. The U-LA self-esteem correlation (ri = −.18) was also below the correlations reported for MZ and DZ reared-together twins (ri = .31 and .13, respectively). Finally, far fewer U-LAs expressed close social relationships (20%) than MZA (80%) and DZA (65%) twins. The present study extends earlier findings indicating that appearance is not meaningfully related to personality similarity and social relatedness. The criticism that MZ twins are alike in personality because their matched looks invite similar treatment by others is refuted. A more judicious interpretation is reactive genotype-environment correlation, namely that MZ twins’ similar personalities evoke similar reactions from others. MZ twins’ close social relations most likely derive from their perceptions of genetically based within-pair similarities that are lacking in U-LAs.
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Canadian photographer François Brunelle and his daughter Laura made many of the U-LAs available. We also wish to thank Mentorn Media for collaborating with the first author in data collection from additional U-LA pairs for their program on look-alikes. This research was partly funded by intramural grants from California State University, Fullerton to Segal. Erika N. Becker provided research assistance.
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Segal, N.L., Hernandez, B.A., Graham, J.L. et al. Pairs of Genetically Unrelated Look-Alikes. Hum Nat 29, 402–417 (2018). https://doi.org/10.1007/s12110-018-9326-2