The New Genetics of Intelligence (Robert Plomin and Sophie von Stumm)
by Saleha Suleman
For centuries, humans have been defined by how intelligent they are. Although the definition of intelligence has changed with evolving times and the differences in lifestyles, the importance of intelligence has not. It is a predictor for occupational, health and overall quality of life outcomes, more than any other trait. This is because a higher intelligence involves the ability to adapt to quickly changing circumstances and undertakings that one would face in their work.
Worldwide, the most standard and widely accepted measurement for intelligence has been IQ (intelligence quotient). An IQ test is able to quantify a person’s reasoning and problem-solving abilities through various tests that the person goes through, and so should be able to account for creativity, thinking outside the box as well as skills needed in schooling subjects such as mathematics. The genetics of intelligence, however, has eluded humans for the longest time. Judging from simple logic, it can be said that there is a certain component of intelligence that is hereditary. But how much it is, and whether it outweighs other factors such as family support, schooling, socioeconomic status and others has not been determined yet. Simply put, intelligence is one of the facets of the ‘nature versus nurture’ debate.
In this paper, the authors performed a meta-analysis to accumulate the findings thus far of the effect of genetics on intelligence. They did this by reviewing results from initial genome wide association studies (GWAS) and showed how genome-wide polygenic scores (GPSs) are a better predictor of intelligence due to it’s accuracy and ability to measure the effects of thousands of DNA variants that are associated with intelligence.
The main findings of the paper are presented in the infographic bellow. Since this is a review, the authors confirmed that there have been multiple attempts to gauge the effect of genetics on intelligence, but the most recent success has come from the use of GPSs. At the time this paper was published, there was also a much larger scale GWAS study being performed that would allow identification of up to 10% of variance. Such studies would allow a clearer definition of the relationship of intelligence with socioeconomic environment, family support, educational attainment of parents and other environmental factors that have so far been attributed to nature in the nature versus nurture debate.
It is important to remember that such studies, and even any tests that would be available to take at a clinic for example, would still be probabilistic and not determinate. Because of that, despite the potential to understand the human mind more, as well as the fact that understanding measurable outcome differences in people of different genetic intelligence would be revolutionary, there have been major ethical concerns for these studies. These include four; biological determination and potential for stigmatization and discrimination, both which can see people being afforded opportunities such as in careers or social circles because of their genetic intelligence, ownership of information, and finally the emotional impact of knowing one’s own personal genetic intelligence levels. As results from current studies become available, it will be of utmost value to distinguish the benefits and shortcomings for them.
Plomin, R. and Von Stumm, S., 2018. The new genetics of intelligence. Nature Reviews Genetics, 19(3), pp.148-159.