Personality similarity in unrelated look-alike pairs: Addressing a twin study challenge

Evidence for the Scarr–Rowe Effect on Genetic Expressivity in a Large U.S. Sample

Using the continuous parameter estimation model (CPEM), a large genotyped adult sample of the population of Wisconsin, USA (the Wisconsin Longitudinal Study) is examined for evidence of the Scarr–Rowe effect, a gene × environment (G×E) interaction that reduces the heritability of IQ among those with low socioeconomic status (SES). This method allows the differential expressivity of polygenic scores predictive of both educational attainment and IQ (EA3) on the phenotype of IQ to be directly operationalized throughout the full range of these variables. Utilizing a parental SES factor-weighted composite as a measure of childhood SES, evidence for the Scarr–Rowe effect was found, that is, the genetic expressivity of EA3 on IQ increased with increasing parental SES (β = 0.08, p = 4.71×10−10, df = 6,255). The effect was found for both the male and female samples separately, β(males) = 0.08, p = 5.27×10−5, df = 3,018; β(females) = 0.08, p = 1.93×10−6, df = 3,236. The effects were furthermore robust to removing outlying values of parental SES and to log-transforming the SES variable. The results are similar to those produced using a more conventional two-way interaction model, with IQ predicting the EA3 × log of parental SES interaction after the main effects; however, CPEM allows for greater model degrees of freedom, thus is better powered to detect the effect when it is small in magnitude (CPEM β = 0.05, p = 6.69×10−5 vs. two-way interaction β = 0.02, pone-tailed = .045, in both models log parental SES is used).

Pairs of Genetically Unrelated Look-Alikes : Further Tests of Personality Similarity and Social Affiliation

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 (r_i = -.02 and - .04, respectively). In contrast, mean r_i 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 (r_i = -.18) was also below the correlations reported for MZ and DZ reared-together twins (r_{i =} .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.

Reared-Apart Chinese Twins: Chance Discovery/Twin-Based Research: Twin Study of Media Use; Twin Relations Over the Life Span; Breast-Feeding Opposite-Sex Twins/Print and Online Media: Twins in Fashion; Second Twin Pair Born to Tennis Star; Twin Primes; Twin Pandas

A January 2017 reunion of 10-year-old reared-apart Chinese twin girls was captured live on ABC's morning talk show Good Morning America, and rebroadcast on their evening news program Nightline. The twins' similarities and differences, and their participation in ongoing research will be described. This story is followed by reviews of twin research concerning genetic and environmental influences on media use, twin relations across the lifespan and the breast-feeding of opposite-sex twins. Popular interest items include twins in fashion, the second twin pair born to an internationally renowned tennis star, twin primes and twin pandas.

Twin Studies of Multiple Myeloma / Research Reviews and News: Critique of Twin Research; Opposite-Sex Twins and Sexual Attraction; Twinning Rates and Assisted Reproductive Technology; Family History of Multiple Implantation / Human Interest: Book Party: Born Together — Reared Apart; Morning Sickness and Twins; Sexuality in Conjoined Twins; Kofi Annan: Opposite-Sex Twin; Switched at Birth

A foundation for studying multiple myeloma, launched by a monozygotic twin, is described. Twin studies of that disease are also examined. A summary of selected research studies and news events follows, with specific reference to a new critique of twin research, sexual attraction in separated opposite-sex twins, twinning rates following assisted reproductive technology and family histories of multiple implantation. Human interest topics cover a gathering of researchers from the Minnesota Study of Twins Reared Apart, morning sickness and twin pregnancy, sexuality in conjoined twins, a famous hidden twin, and a film about switched at birth babies.

The 14th Congress of the International Society for Twin Studies: Selected Highlights/Research Summaries: Twin Study of Telomere Erosion; Genetics of Monozygotic Twinning; Developmental Dysplasia; Fertility of Mothers of Twins / General Interest: Video Portraits; Separated at Birth; Childhood Actors; Adult Twin Film Villains

Selected highlights from the 14th International Congress on Twin Studies, set in Florence, Italy in April 2012, are presented. This meeting, which traditionally occurred every three years, is now being held every two years. Reviews of research on the topics of stress and aging (telomere erosion), the genetics of MZ twinning, developmental dysplasia, and fertility of mothers of twins follow. The final section includes several public interest items, namely an exhibit of twins' video portraits, unusual physical look-alikes, and young and adult twin television and film actors.