A person’s economic and political views are shaped by genetic predispositions in cognitive ability that interact with social class in childhood. People with a high genetic potential for cognitive ability are more likely to adopt left-wing policies if they grew up in a poor environment and right-wing policies if they grew up in a wealthy environment. The study was published in the journal Political Psychology.
Understanding differences in economic policy preferences is a major goal of political science. Traditional models of political economy assume that individuals support policies that are economically advantageous. In a strictly theoretical system of equal redistribution of flat taxes, those with below-average incomes should want complete redistribution, while those with above-average incomes should oppose it. Actual political systems are more chaotic, but the basic power relations generally hold.
Low-income earners tend to benefit from proportional taxation and redistribution, while high-income earners bear the costs. In recent years, researchers have discovered that genetics also influences political behavior. Studies using a variety of methods have demonstrated the overlap between genetic and political preferences. This overlap means that ideological preferences partially share the same genetic structure as other measurable traits.
Our distant ancestors did not have modern tax systems or mass political parties, so evolutionary forces could not directly shape economic ideology. Genetic influences on these preferences must act through intermediate traits that scientists call endophenotypes. Some researchers have proposed that cognitive ability may serve as one of these intermediate characteristics.
However, previous research findings on cognitive ability and economic ideology have been highly contradictory. Several studies have shown a clear link between cognitive ability and economic conservatism. Other studies found a negative association, and some found no association at all.
Rafael Aarskog, a researcher at the Ministry of Government at Uppsala University in Sweden, thought he could reconcile these contradictory results. He proposed an interaction between genes and environment. This occurs when certain genetic factors behave differently depending on the environment surrounding the individual.
Aalskog theorized that cognitive abilities do not in and of themselves push people toward a particular political ideology. Rather, cognitive abilities help people analyze complex policy packages and accurately infer the interests of their own class. The modern economy is filled with a wide variety of taxes, regulations, and benefit programs. Analytical work is required to assess how these policies interact.
By applying these conceptual frameworks, this study connects classical economic theory with modern genetics. People who can easily perform the mental arithmetic required to consider tax proposals optimize their policy preferences. Those who find it more difficult may answer policy questions more randomly or rely on social cues that are not strictly tied to their personal class background.
In addition to this, political science maintains long-standing theories about sensitive periods in human development. This theory states that the influence of the environment on attitudes is strongest during late adolescence and early adulthood. After this period, political preferences tend to stick. On this basis, Aalskog suggested that individuals’ perceptions of class interests are primarily shaped by their parents’ relative economic status during these formative years.
To test these ideas, Aarskog analyzed data from a large sample of fraternal twins born between 1943 and 1958 in the Swedish Twin Registry. Fraternal twins are siblings born at the same time who share, on average, half of their genetic sequence. Exploiting within-family differences between dizygotic twins provides an excellent natural experiment for behavioral researchers.
Researchers emphasize within-family sibling designs because comparing two people from a broader population introduces confounding variables. Between two random strangers, genetic correlations can be distorted by regional ancestry differences and environmental influences on parental genes. Fraternal twins share exactly the same family environment, and their genetic differences arise purely from the random shuffling of their DNA during conception.
Due to this randomization, systematic downstream differences in sibling behavior are interpreted as causal. Researchers can confidently conclude that genetic differences, rather than unmeasured environmental factors, caused behavioral differences.
To perform the analysis, Aarskog used a genetic measure of variation called the polygenic index. Polygenic indices are individual-level predictors of specific traits based entirely on an individual’s DNA. Geneticists construct these indicators by identifying thousands of small DNA variations, known as single nucleotide polymorphisms, that correlate with the target trait. The metrics used in this study summarize each twin’s genetic propensity for cognitive ability, based on previous large-scale genomic discoveries.
He combined this genetic data with the twins’ responses to an extensive survey conducted by the Swedish Twin Registry in 2009-2010. The survey included more than 30 detailed questions about political preferences. Participants rated policy proposals on a 5-point scale ranging from “strongly disagree” to “strongly agree.” Aarskog isolated 12 sections that specifically dealt with economic ideology, including opinions on taxation, welfare distribution, the public sector, and government regulation.
To measure the family’s socio-economic status, Aarskog used data from a Swedish registry covering the parents of twins. He calculated a relative affluence score by comparing parents’ income and education level to other adults in a given local parish. This allowed us to measure the class background locally. Sociologists have found that people typically compare their economic status to their neighbors rather than to the national average.
Looking at the average effect across the sample, genetic measures of cognitive ability had no effect on economic conservatism. The effect size appeared to be virtually zero. Without closer inspection, this may appear to be just a lack of effect.
When Aarskog took family socio-economic background into account, the average null effect collapsed, revealing two distinct and contradictory trends. Among children raised in relatively poor families, a higher genetic index of cognitive ability led to more left-wing economic views. These people supported higher taxes and redistribution of wealth.
Among children from wealthier backgrounds, the effect was completely reversed. A higher genetic index among these privileged people led to more right-wing views. They supported market dependence and cuts in welfare spending. Genetic factors have changed how individuals optimize their political views based on their childhood class.
In the scientific classification of gene-environment interactions, researchers often distinguish between dimmer and lens effects. The dimmer effect occurs when a change in the environment changes the magnitude of genetic influences, making them stronger or weaker. Lensing occurs when the environment actually changes the direction of genetic influences. Aalskog’s findings provide a rare and robust example of a lens effect on socially relevant behavior.
The researchers also controlled for the income and education level of the adult twins. Environmental interactions hold even when considering later life resources. This suggests that genetic influences do not simply influence voters’ current bank account balances, but particularly the formation of class identity early in life.
As a placebo test to test his theory, Aalskog applied the same analytical model to social ideology. Social ideology includes cultural and moral issues such as immigration, criminal justice policy, and animal rights. Unlike economic ideology, optimizing social preferences based on household class has no direct individual economic benefit.
In this test, he found that a higher genetic index was naturally associated with lower social conservatism overall. Its effects worked in parallel on both the rich and the poor. There were no interactions based on socio-economic background.
This study has some limitations and caveats. Genetic predictors are noisy measurements that capture only a portion of the actual genetic traits associated with cognitive ability. Comparing genetic differences within local twin pairs further amplifies this measurement noise. As a result, the reported effects may be much smaller than the actual biological effects.
The geographic and historical realities of the respondent group are also important. The people in this sample grew up in Sweden during the mid-twentieth century, an era defined by the rapid expansion of the modern welfare state. Class-based politics and labor movements were very prominent in their daily lives.
In populations where economic ideology is not the main demarcation line of public debate, the findings may look quite different. In a political environment where left-wing economic positions are supported by socially conservative populists, class dynamics may manifest in other ways. Further research is needed to clarify which specific political relationships are affected by sociocultural changes.
Ultimately, the results of this study indicate that genetic influences on political behavior are highly dependent on the social environment. Effects that appear mathematically zero on average can obscure changes in subsurface dynamics. This heavy dependence on external environmental factors serves as a strong argument against genetic determinism.
The study, “Class, Genes, and Rationality: A Gene-Environment Interaction Approach to Ideology,” was authored by Rafael Aarskog.
