Personality Similarity in Unrelated Look-Alike Pairs: Further Tests of a Twin Study Criticism

The nature of relationships between physical resemblance and personality similarity have generated debate among behavioral science investigators. Research has yielded mixed findings, but positive associations have been... [ view full abstract ]

The nature of relationships between physical resemblance and personality similarity have generated debate among behavioral science investigators. Research has yielded mixed findings, but positive associations have been advanced by some critics to challenge genetically-based interpretations of personality development. Critics argue that monozygotic (MZ) co-twins’ matched physical features invite similar treatment by others, explaining their similar behaviors. Another hypothesis is that MZ co-twins’ matched personality traits are largely due to evocative gene-environment correlation—i.e., twins’ similar behaviors elicit similar responses from others. To assess these competing explanations, the Personality for Professionals Inventory, Rosenberg Self-Esteem Scale and a social relationship survey were completed by 20 unrelated, look-alike (U-LA) male pairs and 24 U-LA female pairs, Mage=42.01 years, (SD=16.24). This study extends findings by Segal (2013) and Segal, Graham and Ulrich (2013), based on 23-25 U-LA pairs: correlations were negligible for all five personality factors. In contrast, big five personality correlations are higher for reared-apart MZA (Mr_i=.53) and dizygotic (DZA) twins (Mr_i=.15). The U-LA correlation was also negligible for self-esteem, compared with the correlations for MZ (r_is=.30-.35) and DZ reared-together twins (r_is=.11-.16). The criticism that monozygotic co-twins’ matched looks explain their similar treatment is refuted in favor of a genetic component underlying twins’ personality similarity. Moreover, a smaller proportion of U-LAs expressed close initial and current social relationships than did MZA and DZA twins, consistent with 2013 findings. It is argued that U-LAs do not perceive behavioral similarities in one another that maintain close social relations.

Segal, N.L. (2013). Personality similarity in unrelated look-alike pairs: Addressing a twin study challenge. Personality and Individual Differences, 54, 23-28.

Segal, N.L., Graham, J.L., & Ettinger, U. (2013). Unrelated look-alikes: A replicated study of personality similarity and new qualitative findings on social relatedness. Personality and Individual Differences, 55, 169-176.