By GIP Project (Genetic Intelligence Project)
Giftedness, characterized by exceptional performance in cognitive tasks, has been the subject of several studies, especially regarding the heredity of this ability. The GIP Project (Genetic Intelligence Project), led by neuroscientist Dr. Fabiano de Abreu Agrela, seeks to elucidate the genetic influence on human intelligence. This project, with a database made up of more than 150 individuals with IQs ranging from 110 to 160 points, offers valuable insight into the hereditary transmission of giftedness.
GIP Project Results
Data collected by the GIP Project reveal distinct patterns of transmission of high cognitive abilities:
1. Parents with high abilities and gifted children: Most cases studied.
2. Gifted father and non-gifted mother with a child with a higher IQ than the father: A significant occurrence.
3. Gifted father and non-gifted mother with a child with a lower IQ than the father: Cases also documented.
4. Gifted father and mother with high abilities with gifted children: All cases observed.
5. Gifted mother and father with gifted children: Consistency observed in all cases.
6. Lack of cases of gifted women with non- gifted parents: A gap in the data that suggests the need for greater sampling.
Analysis of these results suggests a strong genetic component in the transmission of giftedness, particularly when both parents have high cognitive abilities. However, environmental influence and gene-environment interaction cannot be underestimated.
Review of Scientific Literature
Genome-wide association studies (GWAS) establish that human intelligence is highly heritable and polygenic. A genome-wide analysis of 3511 unrelated adults with data on 549,692 single nucleotide polymorphisms (SNPs) and detailed phenotypes in cognitive traits estimated that 40% of the variation in crystallized-type intelligence and 51% of the variation in fluid-type intelligence among individuals is explained by linkage disequilibrium between genotyped common SNP markers and unknown causal variants. If the narrow-sense heritability of intelligence is ~60% across the age groups studied in the CAGES samples, then not all of the additive variation is explained by the analyses. (DAVIES, G. et al., 2011).
Intelligence is one of the most heritable behavioral traits. The heritability of intelligence increases from about 20% in childhood to perhaps 80% in late adulthood. (Plomin and Deary, 2015).
Pedigree-based analyzes of intelligence report that genetic differences account for 50 to 80% of phenotypic variation, while for personality traits, these effects are smaller, with 34 to 48% of the variation explained by genetic differences. (Hill et al., 2018).
The heritability of general intelligence (g) increases with age, going from 0.26 at 7 years of age to 0.45 at 12 years of age, showing an increase in genetic influence at this stage of development. (Trzaskowski et al., 2014).
In a study of 1314 Dutch participants from 317 families, including monozygotic and dizygotic twins, their siblings, spouses, and parents or children, Vinkhuyzen et al. (2012) investigated the influence of mate selection on the heritability of intelligence. The results suggest that the high heritability of intelligence in adults (75% to 85%) can be partially attributed to genetic dominance (27%) and mate selection based on similar phenotypes (11%), in addition to the influence of genetic factors additives (44%) and non-shared environmental (18%).
The studies corroborate the findings of the GIP Project. For example, Plomin and Deary (2015) report that the heritability of intelligence can reach 80% in adult populations, suggesting a substantial genetic contribution (Plomin, R., & Deary, IJ (2015). Genetics and intelligence differences: five special findings. Molecular Psychiatry, 20(1), 98-108). On the other hand, phenotypic variation in intelligence is influenced by multiple genetic loci, each contributing incrementally to overall IQ (Davies, G., et al. (2011). Genome-wide association studies establish that human intelligence is highly heritable and polygenic. Molecular Psychiatry, 16(10), 996-1005).
IQ Ethical Hypothesis Analysis
Below, we present estimates of children’s IQ in four different scenarios, using an average heritability of 70% for intelligence and considering a standard variation of ±15 IQ points.
Scenario 1: Father with 150 and Mother with 120 IQ
First, we calculate the average of the parents’ IQ, which results in 135. Considering that 70% of intelligence is genetically inherited, the genetic contribution would be 94.5 points. The environmental contribution, which represents 30% and is based on the average IQ of the general population (100 points), would be 30 points. Thus, the child’s expected IQ would be the sum of these contributions, resulting in 124.5. Including the natural variation of ±15 points, the expected IQ range for the child would be 109.5 to 139.5.
Scenario 2: Father with 125 and Mother with 125 IQ
In this case, the average IQ of the parents is 125. With a heritability of 70%, the genetic contribution would be 87.5 points, while the environmental contribution would again be 30 points. Therefore, the child’s expected IQ would be 117.5. Considering the standard variation of ±15 points, the expected IQ range would be 102.5 to 132.5.
Scenario 3: Mother with 155 and Father with 130 IQ
For a mother with an IQ of 155 and a father with an IQ of 130, the average of the parents’ IQs would be 142.5. The genetic contribution, representing 70% of this average, would be 99.75 points, and the environmental contribution would be 30 points. Therefore, the child’s expected IQ would be 129.75. With the natural variation of ±15 points, the expected IQ range would be 114.75 to 144.75.
Scenario 4: Mother with 120 and Father with 115 IQ
Finally, for a mother with an IQ of 120 and a father with an IQ of 115, the average of the parents’ IQs would be 117.5. The genetic contribution would be 82.25 points (70% of the average), and the environmental contribution would be 30 points. The child’s expected IQ, therefore, would be 112.25. Including the ±15 point variation, the expected IQ range would be 97.25 to 127.25.
“Yes, giftedness has high heritability. However, genetic heritability can vary due to sentinel variants that significantly influence intelligence. Therefore, this genetic heritability for giftedness is not exact, varying from individual to individual and depending on a random combination of significant alleles present in one of the parents.”
– Dr. Fabiano de Abreu Agrela
Final considerations
Preliminary data from the GIP Project point to a strong genetic influence on giftedness, especially when both parents have high cognitive abilities. However, for a more comprehensive understanding, it is necessary to expand sampling and consider the complexity of gene-environment interaction. Continuing this type of research is crucial to unravel the mechanisms underlying the hereditary transmission of intelligence and to develop appropriate educational and support strategies for gifted individuals.
References
– PLOMIN, R.; DEARY, IJ Genetics and intelligence differences: five special findings. *Molecular Psychiatry*, v. 20, no. 1, p. 98-108, 2015.
– DAVIES, G. et al. Genome-wide association studies establish that human intelligence is highly heritable and polygenic. *Molecular Psychiatry*, v. 16, no. 10, p. 996-1005, 2011.
– PLOMIN, R.; DEARY, IJ The new genetics of intelligence. *Nature Reviews Genetics*, v. 19, p. 148-159, 2018.
– HILL, WD et al. Genomic analysis of family data reveals additional genetic effects on intelligence and personality. *Molecular Psychiatry*, v. 23, p. 2347-2362, 2018.
– TRZASKOWSKI, M. et al. DNA evidence for strong genetic stability and increasing heritability of intelligence from age 7 to 12. *Molecular Psychiatry*, v. 19, p. 380-384, 2014.
– VINKHUYZEN, AAE et al. Reconsidering the heritability of intelligence in adulthood: taking assortative mating and cultural transmission into account. *Behavior Genetics*, v. 42, p. 187-198, 2012.
– JANSEN, PR et al. GWAS of brain volume on 54,407 individuals and cross-trait analysis with intelligence identifies shared genomic loci and genes. *bioRxiv*, 2019.
