The Extent Genetics Plays a Role in Intelligence in Identical Versus Fraternal Twins

Studying the extent to which genetics impacts intelligence in twins has brought forth the consequence this knowledge can have in the way the future of intelligence may be shaped if the idea of the ethical versus unethical ability to alter intelligence is possible. The study of the correlation between genetics and intelligence in identical versus fraternal twins is a concept that dates back to the 1980s. While intelligence is being thoroughly researched across disciplines, the majority of behavioral, genetic, and psychiatric research remains focused on the extent genetics affects intellectual abilities. The present research has concluded that genetics impacts 60% to 80% of the variation of intelligence in twins (Panghal et al, 2020) and environmental factors play less than 20% of the variation of intelligence in twins (Malykh et al, 2005). However little of the sources go into which environmental components affect intellectual abilities.
The purpose of this study is to explore existing studies to investigate the extent to which genetics plays a role in the intelligence of identical versus fraternal twins, to find out how intelligence is shaped in people and if intelligence is based on the concept of nature (genetics) or nurture (the environment individuals grow up in). This study will examine how intelligence is measured and the impact age and socioeconomic (environment) has on the extent genetics plays on intelligence in identical versus fraternal twins.

Hi my name is Destinee Biyoudi-Monthe. And before I get started, let me ask you a question: what do you know about where your intelligence comes from? My research topic is the extent genetics plays on intelligence in identical versus fraternal twins.

The idea if intelligence can be altered is a big debate that has been going on. Studies of this correlation began in the 1980s that focused on twins to test verbal, performance, and full-scale IQ variation in intelligence. It is said that 60% to 80% of the variation in intelligence is due to genetics and less than 20% due to environment, with the implication that identical twins are more likely to be alike intelligence-wise than fraternal twins. In this image (figure 1), we are able to see this study tested high intelligence and how it is affected by genetics and environmental factors, and it shows that identical twins had a higher mean average than fraternal twins. For my research, I wanted to focus on three themes: how intelligence is measured, and how age and environmental factors, such as socioeconomic, impact intelligence. In order to explore if intelligence is based on nature (genetics) and/or nurture (environment).

Two of the main intelligence measurement implied were dynamic testing and cognitive testing. Dynamic testing is a more unbiased approach that tests intellectual growth, compared to cognitive testing which tests intellectual ability.

When it comes to ages’ impact, I had contradictory sources one stated that genetics plays a bigger role in intellectual abilities as you get older and the other one stated the opposite. In this figure (figure 2), this was the Russian twin study, that you can see in the figure the statistics for the variance in verbal, performance, and full-scale IQ data in identical versus fraternal twins. And the differences were not significant enough in this particular study.

With environment, genes play a 45% role in observed variation in processing speed (and the greater processing speed = the greater intellectual ability), 17% is due to shared environment, and 9% to 37% is due to non-shared environment. It’s been said in this image (figure 3), we can see that the richer you are the more genetics plays a role, and the poorer you are the more environment plays a role. But overall, genetics plays a bigger role than the environment when it comes to intelligence in twins.

When it comes to the research, only a few of the sources used dynamic testing to measure intelligence and little is known about how and why the environment impacts intelligence. So, I plan to identify the best intelligence measurement practice to implement and how and why environmental factors, such as socioeconomic, impact intelligence. If I were to do the study, I would choose a sample size of 40 identical twins and 40 fraternal twins in their adolescent years. I would choose a dynamic testing where they would be testing pre the study and post the study to see if the had any intellectual growth within the 1-2 months long the study will take. With this particular study, I will focus on how the amount of educational resources impacts intelligence. So there would be four environments, one would have no educational resources (and each of the sample would be split into each of these environments), the second environment would be little of the resources will be given, third one would be a normal amount, and the fourth one would be loads of resources that would essentially give that group an advantage on the test. If the study was conducted, I would expect genetics to be the leading player in intellectual variability compared to environment.

Thank you. If you have any questions, you can email me.

And these are my references.