A new study from Lund University, tracking roughly 880 twins from the German TwinLife project, reports that between 69 and 98 percent of the link between IQ at 23 and socioeconomic status at 27 can be attributed to genetic factors. IQ itself came in at around 75 percent heritable. These are not modest numbers, and they are not easy ones to sit with.
I read the paper the week after submitting my latest doctoral chapter. The timing was awkward. I had spent years inside an institution that rewards a very specific kind of cognitive output, and here was a study quietly suggesting that the capacity to produce that output may have arrived with me, not been built by me.
The question I had been avoiding finally had data attached to it. How much of what I call effort is actually inheritance wearing effort’s clothes?
What the research found
The study, published in Scientific Reports by personality psychologist Petri Kajonius, followed approximately 880 twins from the German TwinLife project. Participants took IQ tests at age 23. Four years later, researchers measured their socioeconomic status based on education, occupation, and income.
The results were striking. IQ at 23 was strongly predictive of socioeconomic outcomes at 27. The link between the two was largely explained by genetics, ranging from 69 to 98 percent across different outcome measures. That wide spread reflects how differently genetics appears to bear on education, occupation, and income when measured separately. IQ itself was estimated to be around 75 percent heritable in this sample, consistent with a range frequently reported in the behavioral genetics literature, though researchers note that heritability estimates are population-specific and can shift meaningfully across different environments and life stages.
Because the twins were raised in the same households, researchers could attempt to separate genetic from environmental factors. This is a standard design in twin research, though one that carries its own assumptions. The method relies on what scientists call the “equal environments assumption”: that identical and fraternal twins experience their shared home in roughly comparable ways. Critics have questioned how cleanly this holds in practice. With that caveat in view, the pattern in the data was consistent: identical twins, who share all of their DNA, diverged from fraternal twins, who share about half, in ways that pointed toward inherited traits as the primary driver of later outcomes.
“We knew this before,” Kajonius said, “but this study shows even more clearly that we are driven by our genes and become who we are largely because of them.”
What unsettled me most was not the finding about IQ. It was the quieter implication beneath it: that the capacity to benefit from opportunity may itself be partly inherited.
Not just raw intelligence, but the kind of cognitive responsiveness that allows a person to absorb education, translate effort into outcomes, and convert access into advancement.
The part no one talks about
We tend to talk about inequality in terms of access. Who has good schools, stable homes, enough to eat. Those things matter enormously. The researchers themselves were careful to say that targeted interventions can still help people succeed, and that the environment is not irrelevant.
But the study gestures at something harder to address. Even when two people grow up in the same household, with the same resources, the same dinner table, they may still diverge significantly based on what they were born carrying.
This is the finding that tends to produce discomfort in progressive spaces, and I understand why. It can feel like it lets systems off the hook. If outcomes are partly genetic, then what is the point of policy?
I think this reading is wrong, and not just rhetorically wrong. It collapses two separate claims. The claim that genetics shapes individual variance within a given environment is not the same as the claim that environments do not matter. A study showing high heritability inside Germany tells us very little about what would happen if you transplanted the same children into systems with radically different educational floors or ceilings. Heritability is a within-group statistic. Treating it as a verdict on policy is a category error, and a convenient one for anyone who would rather not fund schools.
What the research actually shows is not that effort is meaningless. It is that effort interacts with something prior to it. The person who seems to work harder may also be the person for whom working hard feels more natural, more rewarding, more neurologically reinforced. The ease with which some people absorb feedback, persist through difficulty, or feel motivated by challenge is not simply a matter of character or will.
Kajonius himself noted that the findings might offer some reassurance to parents. Many worry that their mistakes will permanently shape their children’s outcomes. The data suggests parents may have less control over long-term socioeconomic trajectories than commonly assumed.
That does not mean parenting is unimportant. It means the story is more complicated than either pure nurture or pure nature.
What it does to the story I tell about myself
I have spent years inside institutions that reward a particular kind of cognitive performance. Academic writing. Research methodology. The ability to sit with complex material and produce something coherent on the other side of it.
I worked hard. I still do. But the study made me ask a different question: would the work have looked the same if the underlying architecture had been different?
The honest answer is probably not.
There is a version of this that feels deflating, like the credit dissolves. Holding it a little longer produces something else. A kind of softening, toward myself and toward other people.
The student who struggled in my class last semester. The person who read the same book I read and retained almost none of it. The friend who cannot seem to get traction no matter how clearly they understand what they need to do. I think about them differently now.
Not with pity, which would be its own kind of condescension. With a recognition that what looks like effort or motivation from the outside is not always a clean expression of character. The ease or difficulty of engaging with the world is itself shaped by things that arrived before the person did.
The question underneath the question
There is a line Kajonius offers at the end of his findings, almost as a counterweight. He suggests that rather than focusing only on maximising status or income, people may benefit more from pursuing what they naturally enjoy and excel at.
It sounds like something you might read on a motivational poster. The research gives it a different texture. If the internal conditions under which a person thrives are partly heritable, if the shape of what feels engaging or rewarding is not entirely chosen, then the advice is less cheerful and more precise. It is not “follow your passion.” It is closer to: stop treating your cognitive profile as a deficiency to be corrected, and start treating it as a real constraint worth designing around.
That is a meaningful distinction. The first is inspiration. The second is information.
If the relationship between genetics and outcome is as strong as this study suggests, then one of the most self-respecting things a person can do is stop trying to perform a version of success that was never calibrated to them in the first place. Stop measuring yourself against trajectories built for a different cognitive profile.
This is not resignation. It is a form of precision.
What stays after the discomfort passes
I still sit down to write when I do not want to. I still prepare lectures I have given before. None of that has changed, and I am not sure it should.
What has changed is harder to name. The meritocratic story I was handed, the one in which effort is the variable and everything else is background, does not survive contact with this data. Neither does its opposite, the determinist story in which the work I did was decorative. Both are too clean.
What remains is the uncomfortable possibility that I have been rewarded, in part, for traits I did not choose and cannot fully claim, and that the people I have quietly judged for not keeping up may have been running a different race in different shoes the whole time. I do not know what to do with that yet. I am not sure the honest move is to know.
About this article
This article is for general information and reflection. It is not medical, mental-health, or professional advice. The patterns described draw on published research and editorial observation, not clinical assessment. If you’re dealing with a serious situation, speak with a qualified professional or local support service. Editorial policy →
