Martin Arstad Isungset

• Isungset, Martin Arstad; Freese, Jeremy; Andreassen, Ole & Lyngstad, Torkild Hovde (2022). Birth order differences in education originate in postnatal environments. PNAS Nexus. 1(2). doi: 10.1093/pnasnexus/pgac051. Full text in Research Archive Show summary

  Abstract Siblings share many environments and much of their genetics. Yet, siblings turn out different. Intelligence and education are influenced by birth order, with earlier-born siblings outperforming later-borns. We investigate whether birth order differences in education are caused by biological differences present at birth, that is, genetic differences or in utero differences. Using family data that spans two generations, combining registry, survey, and genotype information, this study is based on the Norwegian Mother, Father, and Child Cohort Study (MoBa). We show that there are no genetic differences by birth order as captured by polygenic scores (PGSs) for educational attainment. Earlier-born have lower birth weight than later-born, indicating worse uterine environments. Educational outcomes are still higher for earlier-born children when we adjust for PGSs and in utero variables, indicating that birth order differences arise postnatally. Finally, we consider potential environmental influences, such as differences according to maternal age, parental educational attainment, and sibling genetic nurture. We show that birth order differences are not biological in origin, but pinning down their specific causes remains elusive.

• Isungset, Martin Arstad; Conley, Dalton C; Zachrisson, Henrik Daae; Ystrøm, Eivind; Havdahl, Alexandra & Njølstad, Pål Rasmus [Show all 7 contributors for this article] (2022). Social and genetic associations with educational performance in a Scandinavian welfare state. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 119(25). doi: 10.1073/pnas.2201869119. Full text in Research Archive Show summary

  Recent research has suggested that across Western developed societies, the influence of genetics on educational outcomes is relatively constant. However, the degree to which family environment matters varies, such that countries with high levels of intergenerational mobility have weaker associations of family background. Research in this vein has relied on twin-based estimates, which involve variance decomposition, so direct assessment of the association of genes and environments is not possible. In the present study, we approach the question by directly measuring the impact of child genotype, parental genetic nurture, and parental realized education on educational achievement in primary and secondary school. We deploy data from a social democratic context (Norway) and contrast our findings with those derived from more liberal welfare state contexts. Results point to genetics only confounding the relationship between parent status and offspring achievement to a small degree. Genetic nurture associations are similar to those in other societies. We find no, or very small, gene–environment interactions and parent–child genotype interactions with respect to test scores. In sum, in a Scandinavian welfare state context, both genetic and environmental associations are of similar magnitude as in societies with less-robust efforts to mitigate the influence of family background.

• Lillehagen, Mats & Isungset, Martin Arstad (2020). New Partner, New Order? Multipartnered Fertility and Birth Order Effects on Educational Achievement. Demography. ISSN 0070-3370. doi: 10.1007/s13524-020-00905-4. Full text in Research Archive
• Isungset, Martin Arstad; Lillehagen, Mats & Ugreninov, Elisabeth (2019). One Order Fits All? Birth Order and Education in Immigrant Families. European Sociological Review. ISSN 0266-7215. doi: 10.1093/esr/jcz040. Full text in Research Archive Show summary

  Birth order causes social inequality between siblings. In Western countries, earlier-born perform better than later-born. In non-Western countries, however, earlier-born generally perform worse than later-born. We use administrative data to compare birth order effects between the native population and Norwegian-born children of immigrants (450,864 individuals nested within 202,191 families). The outcome is based on lower secondary school points—a combined measurement of all marks at the end of compulsory education. We found negative effects of birth order on school points for Norwegian natives. This finding is in line with previous studies from Western countries using measures of educational achievement. Birth order effects amongst Norwegian-born children of immigrant parents vary according to maternal country of origin, with some displaying similar effects as natives and others displaying no birth order effects. These findings are surprising in light of the main theories on birth order, which are universalistic and do not predict group-differences. We argue that the universalistic theories need to be supplemented to account for our findings, and discuss the potential importance of cultural variation in family-related behaviours such as strategic parenting, kindergarten attendance, and peer-influence in high-achieving immigrant groups.

• Isungset, Martin Arstad; Lillehagen, Mats & Ugreninov, Elisabeth (2017). Fødselsrekkefølge og utdanningsoppnåelse: Har foreldrenes landbakgrunn betydning? Tidsskrift for samfunnsforskning (TfS). ISSN 0040-716X. 58(1), p. 36–61. doi: 10.18261/ISSN.1504-291X-2017-01-02. Full text in Research Archive Show summary

  Social background is given as one of the main explanations behind educational and work-related outcomes as an adult. There is a long-standing research tradition, however, indicating that there are socioeconomic differences, i.e. birth-order effects, between siblings in the same family. While these have been documented convincingly in recent years, there has been a dearth of studies on important sub-groups. In this article, we use register data to compare birth-order effects among the majority population and children of immigrants. We analyze the largest groups of Norwegian-born to immigrant parents separately. For the majority population, our results are in line with previous studies: At 25 years of age, first-borns have had half a year more education than their fourth and later-born siblings. The main findings for the children of immigrants indicate, on the contrary, few or no differences in terms of birth order, and in light of the previous literature this sheds some new light on the phenomenon. The two main theories on why birth-order effects arise are universal in nature and birth-order effects should thus be found independently of (immigrant) parental background. We suggest that differences in family socialization practices, immigrant status as well as differences related to institutional adaptation are possible explanations.

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• Holst, Cathrine & Isungset, Martin Arstad (2019). Presentasjon av NOU-studie for forskergruppa Social Inequality and Population Dynamics (SIPD). Full text in Research Archive
• Lillehagen, Mats & Isungset, Martin Arstad (2018). New partner, new order? Multipartnered fertility and birth order effects on educational attainment. Full text in Research Archive
• Isungset, Martin Arstad; Baier, Tina & Lyngstad, Torkild Hovde (2021). Gender, Genes, and Income: How Equality of Opportunity Changed in Norway Across the 20th Century. Open Science Foundation. doi: 10.31235/osf.io/e5wjk. Full text in Research Archive Show summary

  The income gender gap shrank dramatically in western democracies over the twentieth century. We ask whether genetic influences on lifetime income, i.e. the heritability, is the same for men and women across birth cohorts. We interpret heritability as achievement and shared environ-ments as social ascription on the basis of gender. We use data on 11,677 twin pairs born in Norway between 1915 and 1991 linked with full-population administrative income data covering the years 1967-2016. The heritability of lifetime income doubled across birth cohorts as women faced fewer social barriers to earn income. The increase in heritability and decrease in gendered shared environments indicate more equality of opportunity between gender for later-born cohorts. However, it also shows that in an extensive welfare state like Norway where gender equality has been a political priority since the 1950s, equality of opportunity was low until very recently. Furthermore, when we study men and women separately, the heritability is lower for women than for men, showing that genes are not pathwayed to influence lifetime income equally. Although we argue that genetically informed designs can be used to evaluate equality of opportunity between genders, we discuss the many interpretive challenges that remain.

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