Genetic tendency for impulsivity is linked to lower education and earlier parenthood

The human tendency to prefer immediate rewards over long-term goals is partly rooted in our DNA, according to a recent study published in the American Journal of Human Biology. The findings suggest that these genetic differences are also linked to major life milestones, including how much education a person completes and when they start a family. Ultimately, the research indicates that both biology and environment shape our approaches to planning for the future.

In psychology and evolutionary biology, scientists study how humans allocate their time and energy throughout their lives. This concept is known as life history theory. Evolutionary biologists focus on how humans balance their resources between their own growth and their reproduction.

Within this framework, humans face a biological trade-off between the quantity and quality of their offspring. A person might have many children but invest fewer resources in each one. Alternatively, they might have fewer children but invest heavily in the skills and success of each individual child.

Some people follow a fast life strategy, which tends to involve shorter periods of education, having children at a younger age, and focusing less on long-term planning. Other people follow a slow strategy, which emphasizes future rewards. This slow strategy includes extended education, delayed parenthood, and greater investment in fewer children.

Historically, psychologists have explained these different strategies by pointing to a person’s surroundings. They suggest that early environmental conditions, such as childhood adversity, unpredictability, or a lack of resources, push individuals toward a faster life strategy to ensure survival. In this psychological view, a fast strategy is a practical response to a world where the future is uncertain.

Evolutionary biologists take a slightly different approach. They highlight inherited variations and biological trade-offs that have developed through natural selection over thousands of years. The scientists conducted this new study to bridge these two perspectives.

“In our study, we asked whether genetic differences may also play a role. Using genetic data, we tested whether a genetic predisposition (polygenic score) toward delay discounting (preferring immediate rewards) is linked to life-history traits,” said study author Martin Fieder, an associate professor at the University of Vienna and co-author of Not So Weird After All: The Changing Relationship Between Status and Fertility.

Delay discounting refers to the human tendency to devalue a reward if there is a long wait to receive it. People who score high in delay discounting prefer a smaller reward right now over a larger reward in the future. This preference serves as a key measure of human impulsivity and future orientation. By looking at genetic data, the scientists aimed to test whether a natural predisposition toward delay discounting is linked to the genetic foundations of life milestones.

Finding a genetic link would suggest that differences in life strategies arise from inherited tendencies as well as environmental factors. To explore these connections, the scientists analyzed data from the Wisconsin Longitudinal Study. This is a long-term project tracking a random sample of individuals who graduated from high schools in Wisconsin in 1957.

The researchers focused on a specific group of 2,713 men and 2,980 women born between 1937 and 1940. They restricted their analysis to unrelated white individuals of European ancestry. This specific restriction helps prevent statistical errors that can happen when mixing genetically diverse populations in this type of analysis.

The researchers utilized a tool called a polygenic score to measure genetic predispositions. A polygenic score is a number that summarizes how an individual’s specific genetic variants might influence a particular trait or behavior. The scientists obtained polygenic scores for delay discounting, educational attainment, age at first child, and total number of children for each participant.

First, the researchers compared the genetic scores against each other to look for molecular overlaps. They controlled for the participants’ birth years and broad genetic background structures to ensure statistical accuracy. Then, they compared the delay discounting genetic scores against the participants’ actual, real-world life outcomes.

These real-world outcomes included the exact number of years of education completed after high school. They also included the specific age the participants had their first child, and their final number of children. Education is considered a vital part of a slow strategy because it represents a long-term investment in skills that pay off later in life.

The scientists found strong relationships at the genetic level for both men and women. A genetic predisposition for high delay discounting was strongly associated with genetic scores for lower educational attainment. The same impulsivity genetic score was also linked to genetic scores for having a first child at a younger age and having a higher total number of children.

When looking at the real-world life outcomes, the patterns pointed in the exact same direction. Participants with a higher genetic score for delay discounting tended to complete fewer years of education. They also tended to have their first child earlier in life and have a slightly larger number of children overall.

“Our findings suggest that tendencies such as being more focused on immediate rewards (fast life history strategy) versus long-term goals may be linked—at least partly—to genetic differences. These tendencies are also related to important life outcomes like education and when people start families,” Fieder told PsyPost.

While the genetic predispositions clearly matched the real-world behaviors, the actual percentage of the behavior explained by the genes was relatively small. The genetic score for delay discounting accounted for about 4.5 percent of the variation in the participants’ years of education. For reproductive traits like the age at first birth and total number of children, the genetic score explained only 1 to 2 percent of the variation.

“The effects should be interpreted carefully,” Fieder said. “Current polygenic scores capture only part of the underlying genetic influences, so the results mainly show directional associations rather than the full size of genetic effects.”

There are a few limitations to keep in mind regarding this study. The genetic data came exclusively from individuals of European ancestry, which means the findings might not apply to people from other genetic backgrounds. Additionally, the original dataset did not include a direct psychological test of the participants’ actual delay discounting behaviors. This required the researchers to rely purely on their genetic predispositions for that specific trait.

The researchers also could not separate the direct genetic effects from the indirect effects of the parents’ genetics. A parent’s genes shape the environment a child grows up in, which can indirectly influence the child’s life choices.

Looking ahead, the researchers aim to expand this work by studying a broader and more diverse group of people. They plan to use genetic scores built from more comprehensive DNA sequencing, which tends to provide a clearer and more detailed picture of human biology. Investigating other biological markers, such as hormone levels or patterns of brain activity, might also help clarify the specific physical processes that connect impulsive tendencies to major life milestones.

“Genetics are important, particularly for human behavior and attitudes, where their role is often underestimated,” Fieder said. “Our tendencies may be less freely chosen than we often assume.”

The study, “Genetic and Phenotypic Associations of the Polygenic Score of Delay Discounting and Life History Traits,” was authored by Martin Fieder and Susanne Huber.