Is intelligence hereditary? Yes. Most public discussion gets the science wrong.

If you're going through IVF and you've got a family history of sharp people (or not-so-sharp people), chances are you've wondered how much of that gets passed on. Maybe you've Googled "is intelligence hereditary" looking for a clean number.

The short answer is: a lot. Cognitive ability is one of the most heritable traits in human genetics.

But here's what changes the conversation for IVF families. Intelligence isn't just a school trait. It predicts health, lifespan, and disease risk across decades. The genetic component is the only part that doesn't fade out. And for the first time, we can measure it between sibling embryos.

Cognitive ability shapes your child's life more than most parents realize

Most people associate intelligence with school performance. That's the most visible part. But cognitive ability predicts a much wider range of outcomes than grades or degrees.

Higher intelligence is associated with longer lifespan. The reduction in all-cause mortality is roughly 20-25% per standard deviation of IQ, based on meta-analytic evidence from large cohort studies. Lower rates of smoking and obesity. Better management of chronic conditions. And substantially reduced risk of dementia: Mendelian randomization studies, which use genetic variation to test causal direction, estimate that each standard deviation increase in intelligence reduces Alzheimer's risk by approximately 35%, independent of education.

Those Mendelian randomization results matter because they aren't just correlations. When the genetic lottery hands someone higher cognitive ability, that person tends to live longer and healthier. The effect runs from intelligence to outcomes, not the other way around.

For education, the numbers are concrete. Using IQ-to-outcome data from the National Longitudinal Study of Youth (about 9,000 individuals tracked with parental SES controlled), a 10-point IQ difference shifts bachelor's degree probability from about 33% to about 56%. That's 1.67x.

Nobody's turning average children into prodigies. That's not what any of this is about. But the difference between a child starting at the 40th percentile versus the 60th percentile of cognitive ability shows up across health, education, and economic outcomes for decades. It's one of the broadest-impact traits in human genetics.

The genetic component is the one that doesn't fade out

Heritability estimates for cognitive ability in adults commonly fall around 50% to 80%. On this question, serious researchers aren't divided. Estimates are lower in childhood and higher in adulthood. Exactly why heritability increases with age still isn't fully understood, though the pattern itself is one of the most replicated findings in behavioral genetics.

Large-scale genome-wide association studies like Savage et al. (2018), which analyzed nearly 270,000 individuals, have identified hundreds of genetic variants associated with intelligence. Those variants aren't randomly scattered across the genome. They're enriched in conserved and coding regions, and the associated genes are strongly expressed in the brain, specifically in neurons involved in learning and memory. This is real biological signal. It's not a test-taking artifact.

But the heritability number alone isn't the reason cognitive screening matters for IVF families. The reason is what happens when you compare genetic influence to the alternatives.

Environmental interventions for cognitive ability mostly don't stick. Large-scale programs like Head Start tried to raise intelligence at considerable cost. The gains faded within a few years. Even schooling, which reliably adds a few IQ points per year of enrollment, appears to produce "hollow" gains. The gains look real on the test. They don't transfer to the general ability that actually predicts whether your child will be healthy, employed, and alive at 80. That's what "hollow" means. A meta-analysis of 141 educational RCTs involving more than 1.2 million students found an average effect size of just 0.06 standard deviations.

The genetic component of intelligence is different. It doesn't fade out. It doesn't wash out when you measure the underlying general ability rather than test scores. And it's the component that predicts the health, education, and longevity outcomes above.

For IVF families, this is the practical point. Sibling embryos differ on the inherited component of cognitive ability. That difference is real, persistent, and consequential. The question is whether we can measure it between embryos. We can.

We can now measure it between sibling embryos

Five years ago, the best publicly available cognitive predictors would have yielded roughly 2.5 IQ points of expected gain from screening 10 embryos (Karavani et al., Cell). Critics called that "limited utility." They weren't wrong. The scores captured only a small fraction of the relevant genetic variation.

A lot has changed since then.

The improvement came from the entire pipeline getting better: larger training datasets, smarter phenotyping (the way you define and measure cognitive ability matters more than most people realize), new meta-analytic methods, and better statistical models. One piece of our approach is SBayesRC, which uses information about what different parts of the genome actually do rather than treating every variant as interchangeable. But SBayesRC is one piece. The gains are across the board. And we're not relabeling educational attainment as intelligence. They're related but not interchangeable.

The metric that matters most for embryo screening is within-family prediction. Your embryos are siblings. They share parents, ancestry, and (eventually) household. Population-level studies pick up signal from all the things that differ between unrelated people: culture, neighborhood quality, parental education. That noise inflates apparent accuracy, especially for traits like cognition where social factors run deep. Population confounding is exactly why within-family validation matters more for cognition than for almost any other trait. If a score still predicts which sibling scores higher after stripping everything they share, the remaining signal is genuinely genetic.

CogPGT showed a within-family correlation of r = 0.456 with general cognitive ability in UK Biobank adults. An independent group recently confirmed a closely matching 0.448. On the latent trait, that's 20.8% of the variance explained. On noisier observed measures the number looks lower, but that's measurement noise in the test, not a disappearance of signal. Full methods are in our CogPGT technical paper and the preprint.

Five years ago, critics were right to call cognitive screening "limited utility." They're not right anymore.

The data also don't support the common story that cognitive screening only works for wealthy families. In the ABCD cohort, we found no significant interaction between CogPGT and family income (p = 0.25), parental education (p = 0.87), or family conflict (p = 0.33).

The autism question is the one parents ask most, so it deserves a direct answer. Older population-level work reports small positive genetic correlations between cognitive measures and autism: around 0.19 to 0.2. The best current hypothesis is that intelligence is mainly correlated with the systematising component of autism — the Asperger's end of the spectrum — rather than with low-functioning autism. In the ABCD data, CogPGT showed a slightly negative association with autistic symptoms. Higher cognitive scores weren't linked to more autism risk. But the honest answer is that we don't fully understand the relationship between intelligence and autism yet. It is genuinely unclear, and we're not going to pretend otherwise.

What IVF families should do with this

If you have only one PGT-A euploid embryo, cognitive screening changes nothing. Your decision is already made. If you have enough euploid embryos that there's a real choice, cognitive screening is rational to include if cognitive outcomes matter to you.

In practice, polygenic embryo screening becomes most useful when you have roughly twice as many euploid embryos as desired children. Fewer can still matter. More is better. The point is having real sibling variation to work with.

This isn't designer-baby science fiction. No one is creating traits outside the parents' genetic range. The embryos already differ genetically. Screening makes some of those inherited differences visible before transfer.

People reach for the word "eugenics" here. It's worth being precise about what that word means. Historical eugenics was state-sponsored coercion: governments decided who was "fit" to reproduce, and the tools were forced sterilization and institutionalization. What we're describing is the opposite. Voluntary, parent-driven decisions about children they're already creating through IVF. No one is coerced. No one is excluded.

We're not going to pretend there aren't real equity concerns. Access to IVF is already stratified by income, geography, and insurance coverage. Cognitive screening exists within that inequity. It didn't create it. But acknowledging the problem honestly doesn't mean withholding validated information from families who are already going through IVF and want it. Our ethics paper addresses this argument directly.

So if you want the shortest honest answer: intelligence is heritable. It affects your child's health, education, and lifespan in ways that are causal, not just correlated. The genetic component is now measurable between sibling embryos with real accuracy. And unlike environmental interventions, it doesn't fade out. When you have a real embryo choice to make, using that information is reasonable.

If you're curious what cognitive screening could look like for your specific embryo count, the expected gains calculator lets you see the numbers. If you want to talk through what any of it means, reach out to our team.