This past weekend, I read somewhere that a good school can compensate for the effects of heredity. I thought of this when I read the study by Ghirardi and colleagues. The researchers focus on the interaction between genetic predisposition and socioeconomic status (SES) in predicting school performance. More specifically, the question was: does the influence of genetic predisposition on cognitive and non-cognitive skills differ depending on the family in which a child grows up? They looked at cognitive skills, such as intelligence, and non-cognitive skills, such as perseverance and social skills.
Polygenic scores (PGIs) play a central role in this research. A polygenic score measures an individual’s genetic predisposition to develop certain traits. The results show that (Dutch) children with a higher genetic predisposition for cognitive skills generally perform better in school. This seems logical. This is reflected in higher grades for math and reading at a young age, better CITO scores at age 12, and a greater chance of entering higher education tracks like HAVO or VWO.
Children with a higher predisposition for non-cognitive skills, such as perseverance and motivation, also perform better in school. However, the effects of these non-cognitive skills are generally smaller than those of cognitive skills. For example, the influence of non-cognitive predisposition on CITO scores is significantly smaller than that of cognitive predisposition.
In addition, the study investigated how a family’s SES affects the relationship between genetic predisposition and school performance. Two theories were tested:
- the Scarr-Rowe hypothesis and the compensatory advantage hypothesis. The Scarr-Rowe hypothesis suggests that children from higher SES families have a better chance of realizing their genetic potential, leading to better school performance.
- On the other hand, the compensatory advantage hypothesis suggests that children from wealthy families, even with lower genetic predispositions, still achieve higher educational outcomes due to their favourable environment.
The results support the compensatory advantage hypothesis. This means that children from higher SES families still perform well in school even if they have less genetic predisposition for cognitive skills. Wealthy parents can compensate for their children’s genetic disadvantages by providing additional support, such as homework help or tutoring. This ensures that children from affluent families are less dependent on their genetic predisposition than children from less well-off families.
The research employed three methods: a between-family, within-family, and trio analysis. Each method was designed to minimize various forms of bias and distortion. The between-family analysis compared children from different families to separate genetic and environmental influences. The within-family analysis looked at differences between siblings within the same family to better understand genetic effects. The trio analysis combined data from both children and their parents, allowing the researchers to also account for the genetic influence of the parents.
Although the study provides important insights, there are some limitations. The sample size is relatively small, particularly in the within-family and trio analyses. Larger samples could improve the accuracy of the results, especially when identifying interactions between genetic predisposition and SES. Additionally, the concept of non-cognitive skills is less well-defined than that of cognitive skills. Further studies are needed to better quantify and understand these non-cognitive skills.
Finally, the study emphasizes that the results must be replicated in other countries and education systems to determine how general these findings are. With its early selection and clear separation between educational tracks, the Dutch education system provides a unique context. In countries with other education systems, the results could potentially be different.
What is the key lesson? Although genetics is an important factor, the family environment and parental support appear crucial to getting the most out of children. In practice, this seems to happen mostly in families with higher SES.
Abstract of the study:
This study examines the role of genes and environments in predicting educational outcomes. We test the Scarr-Rowe hypothesis, suggesting that enriched environments enable genetic potential to unfold, and the compensatory advantage hypothesis, proposing that low genetic endowments have less impact on education for children from high socioeconomic status (SES) families. We use a pre-registered design with Netherlands Twin Register data (426 ≤ N individuals ≤ 3875). We build polygenic indexes (PGIs) for cognitive and noncognitive skills to predict seven educational outcomes from childhood to adulthood across three designs (between-family, within-family, and trio) accounting for different confounding sources, totalling 42 analyses. Cognitive PGIs, noncognitive PGIs, and parental education positively predict educational outcomes. Providing partial support for the compensatory hypothesis, 39/42 PGI × SES interactions are negative, with 7 reaching statistical significance under Romano-Wolf and 3 under the more conservative Bonferroni multiple testing corrections (p-value < 0.007). In contrast, the Scarr-Rowe hypothesis lacks empirical support, with just 2 non-significant and 1 significant (not surviving Romano-Wolf) positive interactions. Overall, we emphasise the need for future replication studies in larger samples. Our findings demonstrate the value of merging social-stratification and behavioural-genetic theories to better understand the intricate interplay between genetic factors and social contexts.