New research published in scientific report suggest that the relationship between young people’s cognitive ability and future socio-economic status is primarily driven by genes. The findings provide evidence that genetic factors play a greater role in educational and occupational success than environmental conditions. This underlying biology may help explain why some social interventions aimed at reducing inequality tend to be insufficient in the long term.
Social scientists have spent decades understanding the psychological mechanisms that produce socioeconomic status. Obtaining an education and securing a job are the main ways young people earn a living and begin to establish themselves in society. Past research has reliably shown that general cognitive ability, often measured as intelligence quotient, is the strongest predictor of a person’s future socio-economic status.
However, it remains unclear whether this relationship is primarily caused by a person’s unique genetics or by their personal life experiences. These experiences may include the social networks you build during college or specific opportunities you encounter in the job market. Petri J. Kajonias, an associate professor in the Department of Psychology at Lund University in Sweden, a personality researcher, and an organizer of PersonRightpodden, conducted this study to answer that question.
“Most people, including psychology researchers, do not realize that most correlations in psychological science are primarily driven by genetics, rather than environment. This unawareness is due to Sweden’s famous focus on social equality through intervention. This is particularly true for researchers, but not many social science studies have attempted to control for individual genetics. This is probably one of the first studies based on genetic information in Sweden to examine the well-known and very strong relationship between IQ and socio-economic status.
In particular, Kajonius wanted to quantify exactly how much of the association between young people’s cognitive abilities and their later socio-economic status was due to genetic inheritance. To find out, researchers used data from the TwinLife project, a large, representative study of German families. The sample included 440 twin pairs, consisting of 228 identical twin pairs and 212 dizygotic same-sex twin pairs.
By analyzing twins, scientists can estimate how much of a particular trait is due to inheritance. Identical twins share all of their genes, while fraternal twins share about half of their genes on average. By comparing the similarities between these two types of twins, researchers can mathematically calculate how much of a trait is due to genetics or to environmental exposure.
The participants in this particular analysis were young people who were making a career transition. In the first wave of data collection, the average age was approximately 23 years, and in the second wave 4 years later, the average age was approximately 27 years. During the first phase of the study, participants completed a computer-based cognitive assessment.
This assessment measured the ability to reason and solve problems using unfamiliar information, a core element of general intelligence. Four years later, the researchers measured the participants’ socioeconomic status using four different variables. Two of these variables focused on educational background, categorizing the complexity and level of schooling completed by each participant on a scale of 0 to 10.
Two other variables measured occupational status to provide a complete picture of career success. One person ranked the social prestige of their current job. The other classified occupations based on the level of autonomy and status they have in the broader labor market. Researchers used statistical models to separate the effects of genetics from those of the environment.
This data reveals that cognitive abilities in young adulthood are highly heritable. Specifically, about 75 percent of the differences in cognitive ability between individuals can be explained by genetic makeup.
Socioeconomic outcomes at age 27 also showed a significant genetic influence. Genetic factors explained 49 to 66 percent of the difference in educational attainment between participants. For occupational status, genetics accounted for 32 to 71 percent of individual differences.
Genetic factors played a dominant role in the relationship between cognitive ability at age 23 and socioeconomic status at age 27. Common genetic traits explained 69 to 81 percent of the association between cognitive ability and educational outcomes. Genetics explained up to 98 percent of the association between cognitive ability and occupational status.
This means that the same genetic predispositions that contribute to higher cognitive abilities also tend to promote socio-economic success. The overlap in genetic factors was several times greater than the overlap in environmental factors. These environmental factors typically consist of shared family resources or random life events such as meeting the right person at the right time.
The shared genetic influence between cognitive ability and socioeconomic status may operate in several different ways. The same genes may simultaneously influence brain development and behaviors that promote career success, creating a direct biological link. Alternatively, genes may enhance cognitive abilities, making it easier for people to obtain higher education and obtain higher-paying jobs.
“The important message for the average person is that psychology manifests in life primarily through genetic makeup and less so through environmental conditions,” Kajonias told SciPost. “When it comes to life outcomes such as education, occupation, and income, there is no doubt that individuals are more important than the ratings they are given. This may therefore be one reason why social interventions aimed at equality often fail in the long term.”
Although these findings highlight the profound influence of biology on life outcomes, it is important not to mistake heredity for absolute destiny. A high genetic explanation for a trait only indicates an increased probability, not a predetermined certainty.
“Heritability does not necessarily mean determinism, it just increases the probability,” Kajonius says. “It’s a common example, but the genetic problem of poor eyesight can be easily solved by wearing glasses.”
This study has some limitations. The 4-year interval between the first and second measurements is a relatively short period of time. Tracking these young people from ages 23 to 27 may not provide enough time for their cognitive abilities to fully shape their long-term career trajectories.
Additionally, the statistical model used in the study simplified analysis by strictly partitioning effects into genes and environment. This approach did not take into account more complex interactions, such as how certain genes respond differently in completely different environments. Future research should aim to investigate these complex interactions over longer periods of a person’s life.
Ultimately, Kajonias hopes this line of research will help both scientists and the public understand that psychological differences are largely influenced by our biology. Recognizing that people have different genetic predispositions can help policy makers design more effective social interventions. Treating populations as completely homogeneous often leads to programs that do not have the intended long-term results.
The study, “The long-term association between cognitive ability and socioeconomic status is partially genetic in nature,” was authored by Petri J. Kajonius.
