From the Guidelines
A child's intelligence is influenced by both parents, with no single parent contributing more than the other, and environmental factors such as nutrition and stimulation playing a significant role in cognitive development. The genetic contribution to intelligence is complex and involves multiple genes from both parents, making it a balanced inheritance 1. While there is evidence suggesting that certain factors, such as breastfeeding, may have a positive impact on child neurodevelopment and cognition, with meta-analyses associating breastfeeding initiation and duration with higher performance in intelligence tests in children and adolescents, the genetic basis of intelligence remains a key factor 1.
Key Factors Influencing Intelligence
- Genetic inheritance from both parents
- Environmental factors, including:
- Nutrition, with breastfeeding shown to have a positive impact on child neurodevelopment and cognition 1
- Education quality
- Emotional support
- Intellectual stimulation
- Epigenetic factors, which influence how genes are expressed based on environmental conditions
The study on human milk and child neurodevelopment highlights the importance of the first 1000 days of life in brain and behavioral development, during which nutrition and environmental input play crucial roles in shaping the child's cognitive abilities 1. However, when considering the question of who a child gets their majority of intelligence from, it's essential to prioritize the most recent and highest quality evidence, which indicates a balanced genetic contribution from both parents.
Prioritizing Evidence
The most recent study 1 provides insight into the complex interplay between genetic and environmental factors in intelligence development, emphasizing the role of both parents and the environment. In contrast, older studies, such as the one on the management of grown-up congenital heart disease 1, may not directly address the question of intelligence inheritance and are therefore less relevant to this specific inquiry.
Clinical Implications
In real-life clinical practice, understanding the balanced genetic contribution to intelligence and the significant impact of environmental factors can inform strategies to support cognitive development in children. This includes promoting breastfeeding, ensuring access to quality education, and providing emotional and intellectual stimulation. By recognizing the complexity of intelligence development, healthcare providers can offer more comprehensive support to families, focusing on both genetic and environmental aspects to foster optimal cognitive growth and development.
From the Research
Genetic Influence on Intelligence
- The majority of intelligence is influenced by genetic factors, with heritability estimates ranging from 20% to 80% depending on the age and population studied 2, 3, 4, 5.
- Genome-wide association studies (GWAS) have identified specific gene loci associated with intelligence, as well as educational attainment, which is correlated with intelligence 2, 3.
- Polygenic scores, which summarize the effects of thousands of genetic variants, can explain 7-15% of inter-individual differences in educational attainment and 7-10% in intelligence among persons of European descent 2.
Parental Contribution to Intelligence
- While there is no direct evidence to suggest that a child gets the majority of their intelligence from one parent, research suggests that genetic factors contribute significantly to intelligence 2, 3, 4, 5.
- Assortative mating, where individuals with similar traits (including intelligence) mate, can contribute to the high narrow heritability of intelligence, suggesting that both parents may contribute to a child's intelligence 5.
Environmental Influence on Intelligence
- Environmental factors, such as social conditions, can also influence intelligence, and the relative importance of genetic factors can vary depending on individual environmental conditions 2, 5.
- The interaction between genetic and environmental factors is complex, and more research is needed to fully understand the relationship between genetics, environment, and intelligence.