Is This the Study That Rewrites IQ Theory?

For as long as intelligence has been studied, we’ve been told that our raw IQ is mostly a genetic hand-me-down.

Sure, we've learned how to sharpen the knives we were handed and increase our “effective IQ" through good habits, deliberate practice, and focus. But the raw numbers themselves, which we typically derive from Binet tests or Raven’s Progressive Matrices, have been thought by many in the field to be all but carved in stone.

Now, new research from Horvath and Fabricant challenges that assumption, and it does so with the kind of study design psychologists dream of: examining identical twins reared apart. Their findings suggest that education, of all things, may hold surprising power to raise measured intelligence.

For educators, this study could be a validation of an instinct we've tapped on for years. For the rest, it offers hope that misreadings of prior research had closed off.

What We Thought We Knew About IQ

The nature-nurture debate has always been an uneasy truce.

In the early 20th century, behaviorists like John B. Watson believed that the environment could shape any child into any type of adult. But by the 1970s and 1980s, the pendulum was already swinging hard toward heredity.

Studies of identical twins, such as the landmark Minnesota Study of Twins Reared Apart, led by Thomas Bouchard, showed correlations of around 0.75 in IQ between twins separated at birth. That’s roughly the same heritability as height, which often ranges in the 0.80s.

Robert Plomin’s decades of work extended that insight, using genome-wide association studies to show that intelligence is strongly polygenic and stable across the lifespan. His research suggested that as we age, genetic factors account for an even greater share of IQ variance, a concept known as the “genetic amplification hypothesis.”

In this light, education can look more like a sorting mechanism than a sculptor. Many took this as intellectual fatalism, beginning to believe that our ceilings were fixed and schooling merely revealed who we were meant to be.

Yet others saw something missing from that picture. Even if the hardware is largely set, the software with which we deploy our curiosity and reasoning can be dramatically upgraded. Psychologists have long known that effective IQ, or the ability to get more from the same mental engine, can improve through metacognition, motivation, and something as simple as "enclothed cognition" (Galinsky, 2012).

Horvath and Fabricant have added spice to the stew, showing that education itself can lift not just performance, but the underlying IQ scores, even when genes are held constant.

Education as the Great Intelligizer

The idea that education influences intelligence isn’t new.

Decades ago, researchers like Arthur Jensen and James Flynn debated the direction of causality: Do smarter kids stay in school longer, or does staying in school make kids smarter? Flynn’s own discovery of the steady rise of IQ scores across generations hinted that something environmental, perhaps schooling or nutrition, was at play.

A large meta-analysis by Stuart Ritchie and colleagues in Psychological Science (2018) quantified how education leads to improved cognitive skills, with increases decoupled from the underlying raw IQ. Some critics argue that education studies are unable to untangle self-selection to begin with, given how smart kids seek more education to begin with.

Horvath and Fabricant approached it differently. By studying identical twins reared apart, individuals who share 100 percent of their genes but experience different environments, they could isolate the effect of schooling itself.

They grouped pairs based on how divergent their educational paths were, from minimal difference to radically distinct. The results were startling, with twins that had the largest gap in years of education differing by as much as 15 IQ points.

That’s a full standard deviation's worth of a difference, enough to shift someone from the average range into the gifted category. For the first time, we have twin-based evidence suggesting that education does more than polish existing ability; it adds new horsepower.

The Brain That Keeps Learning

The implications of the study go well beyond education policy. If schooling can boost IQ even when genes are identical, then intelligence may be more dynamic, and more democratic, than previously thought.

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Neuroplasticity offers a biological explanation. Studies by Draganski et al. (2004) showed that adults who learned juggling developed measurable increases in grey matter volume in the visual and motor areas of the brain. Similar results have been found in musicians and bilinguals. The brain, it seems, responds to cognitive challenge like a muscle to exercise. Horvath and Fabricant’s findings also echo recent research showing that philosophy training can improve critical reasoning and abstract thought (Prinzing and Vazquez, 2025).

The line between “raw” and “effective” intelligence is blurring, and perhaps what we’ve called “innate ability” is better understood as potential, one that education can still unlock well into adulthood.

What Horvath and Fabricant’s work does is restore a sense of agency. The walls of the IQ fortress, once thought impregnable, now show cracks wide enough for growth through disciplined curiosity to slip through.

For anyone who’s ever felt capped by a test score or a label, know this: We can still grow smarter. We might not be able to do it overnight, nor through gimmicks. But what we now know is that the brain, like the mind, keeps learning as long as we keep teaching it.