Specific cognitive skills like reading, math, and processing speed are strongly influenced by genetics, even when separated from a person’s overall intelligence. A massive new meta-analysis reveals that specific cognitive abilities rely on inherited DNA just as much as general intelligence does. This distinction opens the door for future genetic profiles to help guide individualized education. The study was published in Intelligence.
Historically, psychology and behavioral genetics have focused heavily on general cognitive ability, often referred to as general intelligence. This concept sits at the very top of a widely used psychological framework called the Cattell-Horn-Carroll model of intelligence. General intelligence represents the overlapping mental energy or broad processing power that helps individuals perform well across a wide variety of mental tasks. It acts as an underlying engine that drives performance across diverse mental challenges.
Underneath this broad umbrella, the model features a middle tier of 16 specific cognitive abilities. These specialized domains include skills like quantitative knowledge, reading and writing, short-term memory, visual processing, and processing speed. The lowest tier of the model contains hundreds of individual cognitive tests used in schools and clinical settings. Researchers group these individual tests into the middle tier to better understand how specific domains function.
Past behavioral research has established that general intelligence is roughly 50 percent heritable. Heritability is a statistical measure that describes how much of the variation in a specific trait within a population can be attributed to inherited genetic differences. It does not mean a single individual’s intelligence is strictly half genetic and half environmental. Instead, it explains the differences connecting people within a given group.
Family and adoption studies have shown a surprising developmental trend regarding general intelligence. The heritability of general intelligence actually increases as people grow older. It climbs from about 20 percent in infancy to 40 percent in childhood, eventually reaching 60 percent in adulthood. People seem to grow into their genetic predispositions as they gain the independence to select environments that match their innate abilities.
Far less data has been available regarding the genetics of the middle tier of specific cognitive abilities. King’s College London researcher Francesca Procopio and her colleagues wanted to understand if these specific abilities were as heritable as general intelligence. They also wanted to know if certain specific abilities were more heavily influenced by genetics than others. Early reviews from the 1970s and 1980s hinted at similar genetic roots, but those early studies relied on very small sample sizes.
A major focus of their modern inquiry was whether the genetic influence on specific cognitive abilities is simply a byproduct of general intelligence. People with high general intelligence tend to perform well on specific tests, creating an overlapping statistical effect. The researchers wanted to isolate specific abilities to see if they possessed their own distinct genetic foundations. If they could separate specific skills from general intelligence, they could map out unique cognitive profiles.
To answer these questions, Procopio and her team conducted a meta-analysis combining data from 77 previous publications. They focused on twin studies, a classic and highly reliable method in behavioral genetics. By comparing identical twins, who share 100 percent of their genes, to fraternal twins, who share about half of their genes, researchers can estimate the genetic contribution to a given trait. Any extra similarity observed in identical twins is attributed to their shared DNA.
The authors compiled 747,567 twin comparisons spanning 11 of the 16 specific cognitive domains within the broader theoretical model. They mapped the numerous different tests used in the original studies into these broad categories to create a unified framework. This aggregation allowed them to calculate average heritability estimates for the specific abilities and compare them across different age groups. The final data set provided enough statistical power to detect small differences between cognitive domains.
The combined results showed that the average heritability across all specific cognitive abilities is 56 percent. This number is slightly higher than the average heritability of overall general intelligence. However, the exact level of genetic influence varied widely among the different specific domains. Some areas of cognition appear far more dependent on inherited differences than others.
Quantitative knowledge, reading and writing, and processing speed were the most heritable traits, with estimates sitting above 60 percent. In contrast, fluid reasoning and short-term memory fell closer to 40 percent. Fluid reasoning involves the capacity to solve novel problems and is often thought to be a core component of general intelligence. This specific contrast presented an unexpected puzzle for the research team.
Many psychologists assume that acquired knowledge domains depend primarily on school instruction and shared childhood experiences. The data showed that these learned subjects were more strongly linked to genetics than innate fluid reasoning. This finding challenges the assumption that subjects taught in school represent pure environmental achievement rather than innate biological ability. It suggests that individuals have strong genetic predispositions toward acquiring specific types of academic knowledge.
The team also noticed surprising differences within functionally similar categories. Processing speed, which involves automatically performing easy cognitive tasks under focused attention, was highly heritable at 64 percent. Meanwhile, reaction and decision speed, which involves making basic responses to simple stimuli, possessed one of the lowest heritability estimates at 42 percent. The authors propose that tasks requiring higher levels of mental complexity might simply capture more genetic influence.
The meta-analysis then evaluated developmental patterns, revealing different aging trajectories for specific abilities compared to general intelligence. The genetic influence on general intelligence predictably increases from childhood through adulthood as individuals select their own intellectual environments. Specific cognitive abilities do not display this same climbing trend over the lifespan. Instead, they follow a much flatter trajectory after an initial childhood bump.
The heritability of specific abilities rises from early to middle childhood and then slightly declines or plateaus. For example, reading and writing heritability showed a general trend of decreasing influence from middle childhood onward. The researchers suggest that difficulties in reliably testing young children might artificially inflate the apparent jump in childhood heritability. Some researchers suspect that universal education reduces environmental disparities, which allows genetic predispositions for these subjects to stabilize during the school years.
When the researchers mathematically adjusted the data to remove the influence of general intelligence, they uncovered another unexpected result. The isolated specific cognitive abilities remained highly heritable, averaging 53 percent. This means that a large portion of the genetic foundation for skills like math or spatial reasoning is entirely independent. It is distinct from the genes that drive a person’s overall intellectual horsepower.
The study does include some limitations based on the available historical data. Five of the 16 specific cognitive categories completely lacked twin comparisons, meaning certain domains like motor or olfactory abilities could not be analyzed. Additionally, only two cognitive categories had enough available data to track across the entire human lifespan. This lack of continuous data makes it difficult to draw absolute conclusions about cognitive aging.
Splitting the data into different age groups naturally reduced the statistical power of the developmental analysis. The researchers also note that studies from different decades and countries often use different exact testing methods, adding noise to the combined data. Organizing diverse cognitive tests into broad categories inevitably requires some subjective categorization. The mathematical methods used to separate general intelligence from specific abilities are also approximations because no paper-and-pencil test is perfectly reliable.
Going forward, the team hopes these findings will encourage more detailed genetic research using modern DNA sampling. They want to identify the exact genetic variants associated with specific abilities to build customized cognitive profiles. Identifying these sequences could eventually allow scientists to predict individual cognitive strengths and weaknesses from a young age. This knowledge would act as an additional tool for educators and parents.
By understanding these profiles independently of general intelligence, educators might one day tailor early interventions. Instead of waiting for a student to struggle in a specific subject, teachers could anticipate learning hurdles and adjust their teaching methods. Fostering a child’s innate strengths while minimizing their weaknesses could help them reach their full educational potential. Ultimately, this research shifts the focus from a single intelligence score to a diverse landscape of individual abilities.
The study, “The genetics of specific cognitive abilities,” was authored by Francesca Procopio, Quan Zhou, Ziye Wang, Agnieska Gidziela, Kaili Rimfeld, Margherita Malanchini, and Robert Plomin.