Educational attainment of same-sex and opposite-sex dizygotic twins: An individual-level pooled study of 19 twin cohorts

Karri Silventoinen*, Leonie H. Bogl, Aline Jelenkovic, Eero Vuoksimaa, Antti Latvala, Weilong Li, Qihua Tan, Dongfeng Zhang, Zengchang Pang, Juan R. Ordoñana, Juan F. Sánchez-Romera, Lucia Colodro-Conde, Gonneke Willemsen, Meike Bartels, Catharina E.M. van Beijsterveldt, Esther Rebato, Robin P. Corley, Brooke M. Huibregtse, John L. Hopper, Jessica TylerGlen E. Duncan, Dedra Buchwald, Judy L. Silberg, Hermine H. Maes, Christian Kandler, Wendy Cozen, Amie E. Hwang, Thomas M. Mack, Tracy L. Nelson, Keith E. Whitfield, Emanuela Medda, Lorenza Nisticò, Virgilia Toccaceli, Robert F. Krueger, Matt McGue, Shandell Pahlen, Nicholas G. Martin, Sarah E. Medland, Grant W. Montgomery, Kauko Heikkilä, Catherine A. Derom, Robert F. Vlietinck, Ruth J.F. Loos, Patrik K.E. Magnusson, Nancy L. Pedersen, Anna K. Dahl Aslan, Matthew Hotopf, Athula Sumathipala, Fruhling Rijsdijk, Sisira H. Siribaddana, Richard J. Rose, Thorkild I.A. Sørensen, Dorret I. Boomsma, Jaakko Kaprio

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Comparing twins from same- and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same- and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (β = −0.05 educational years, 95% CI −0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an opposite-sex co-twin (β = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between same-sex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.

Original languageEnglish
Article number105054
JournalHormones and Behavior
Volume136
ISSN0018-506X
DOIs
Publication statusPublished - Nov 2021

Keywords

  • Education
  • Testosterone exposure
  • Twin testosterone transfer hypothesis
  • Twins

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