New groundbreaking research from the University of Colorado Boulder has uncovered compelling evidence that cognitive ability in adulthood can be traced back to infancy. Published recently in the prestigious journal Proceedings of the National Academy of Sciences (PNAS), this long-term study leverages twin data and genomic information to illuminate the pathways through which early cognitive signals forecast intellectual performance decades later. This innovative investigation offers robust insight into the trajectories of general cognitive ability (GCA) from as early as seven months of age, challenging long-held assumptions regarding the stability and malleability of intelligence across the lifespan.
General cognitive ability, often colloquially termed IQ, represents a composite measure of a person’s capacity for learning, reasoning, problem-solving, and understanding complex information. While it is well-established that intelligence measured in childhood remains relatively stable into adulthood and even late life, few studies have explored the extent to which infancy holds predictive power for these traits. This research, led by assistant research professor Daniel Gustavson and senior author Chandra Reynolds at the Institute for Behavioral Genetics, fills this gap by tracing cognition from infancy to age 30 in over a thousand twins. Their findings underscore that even rudimentary cognitive behaviors observed as early as seven months can portend adult cognitive function with significant implications for understanding lifelong neurodevelopmental trajectories.
The study draws on an extraordinary dataset from the Colorado Longitudinal Twin Study, an ambitious and ongoing project initiated in 1985 to disentangle the genetic and environmental contributions to cognitive and behavioral development. This cohort includes 1,098 participants meticulously monitored via laboratory assessments, home visits, surveys, and behavioral tests conducted periodically through childhood and beyond. Importantly, the twin design allows an elegant comparison between monozygotic (identical) twins, who share 100% of their DNA, and dizygotic (fraternal) twins, who share approximately half. This comparative framework is essential for parsing the relative influence of heritability versus environment on complex traits such as intelligence.
At the core of the infant assessments were seven key cognitive metrics, including vocalization frequency, attentional control as measured by task orientation, and novelty preference, the propensity to engage with unfamiliar stimuli rather than familiar toys. These early measurements are modest but meaningful indicators of cognitive engagement and processing. Remarkably, the data demonstrated that these infant cognitive indicators accounted for approximately 13% of the variance in cognitive scores at age 30, with novelty preference and task orientation emerging as the strongest predictors. Such predictive validity from infancy to adulthood, spanning more than two decades, is unprecedented in observational cognitive research.
Crucially, this stability does not imply cognitive determinism. Gustavson emphasizes that cognitive function in infancy is not fixed but rather signals underlying neurodevelopmental processes that continue to unfold and respond to environmental contexts. The research highlights the plasticity and sensitivity of early cognitive systems to external stimuli, underlining the profound importance of early-life environments. Indeed, the study finds that environmental factors before age two explain about 10% of adult cognitive variability. This finding challenges prior assumptions that genetic factors overwhelmingly dominate early-life cognitive outcomes and accentuates the critical role that interventions and enriching environments can play from infancy onward.
The dynamic interplay between nature and nurture is further elucidated through twin comparisons and genomic analyses. While heritable factors measured at age seven explained roughly half of the variance in adult cognitive ability, environmental effects, particularly during infancy and early childhood, were non-negligible and had lasting influence. Fascinatingly, as children mature, genetic influences on cognition intensify while environmental impacts wane, tracking with critical periods of neural maturation and the decreasing plasticity of brain circuits. This temporally shifting balance opens avenues for strategic timing of educational and developmental interventions.
The study’s incorporation of polygenic scores represents a cutting-edge integration of behavioral genetics and genomic epidemiology. Polygenic scores synthesize the collective impact of thousands of genetic variants, each conferring subtle contributions to cognitive traits. By leveraging data sets encompassing nearly one million individuals, including large-scale commercial biobank resources like 23andMe, the researchers calculated individualized polygenic scores for the twins. These scores showed a strong correspondence with observed cognitive abilities in adulthood and interestingly aligned with infant cognitive measures, lending credence to the notion that genetics and early cognitive markers converge in predicting lifelong cognition.
These findings carry far-reaching implications beyond academic knowledge. Professor Reynolds, who specializes in age-related cognitive decline and diseases such as Alzheimer’s, underscores that understanding early cognitive stability and environmental modulation can inform approaches to mitigate dementia risk. Cognitive aging is a continuum beginning in infancy rather than an abrupt decline initiated in midlife. Early educational foundations and enriched environments may therefore serve as "cognitive reserves," bolstering resilience against neurodegenerative conditions. This perspective appeals to policymakers, educators, and healthcare providers aiming to optimize cognitive health across the lifespan.
Moreover, this research invites a reevaluation of how we conceptualize intelligence testing and cognitive assessments. Current adult cognitive tests, often perceived as complex and multifaceted, may have foundational predictors detectable within simple infant behaviors. By acknowledging these early signals, developmental trajectories can be mapped more accurately, enabling personalized interventions that capitalize on critical windows of plasticity. The integration of twin studies with genomic data offers a blueprint for future research endeavors seeking to unravel the intricate scaffolding of cognitive development.
While the early cognitive markers identified explain a fraction of the total variance in adult cognition, even modest predictive capabilities are impactful when considering the complexities of human brain development. The work champions a nuanced understanding: genetic predispositions provide a baseline framework, but environmental contributions—especially during infancy—can modulate, enhance, or impede cognitive outcomes throughout life. Consequently, early childhood becomes a paramount period for cultivating cognitive potential, underscoring the societal value of programs dedicated to early education, parental support, and environmental enrichment.
This study is emblematic of interdisciplinary collaboration across psychology, neuroscience, genetics, and epidemiology, demonstrating the power of longitudinal twin designs unified with genomic technology to explore human cognition. The Colorado Longitudinal Twin Study exemplifies how sustained investment in comprehensive, multimodal data collection can harness insights inaccessible through cross-sectional or purely behavioral approaches. Such research expands the frontier of developmental cognitive neuroscience and lays the groundwork for future discoveries encompassing molecular, environmental, and psychosocial dimensions.
In conclusion, the University of Colorado Boulder research team has substantially advanced our understanding of how infancy shapes adult cognition, affirming the enduring influence of early life alongside genetics. The predictive stability of cognitive ability from a simple test in seven-month-old infants to sophisticated adult cognitive assessments three decades later highlights the impressive continuity of neurodevelopment. Combining rigorous twin methodologies with cutting-edge genomic analytics, the study reveals not only the complexity of intelligence but also the critical importance of early environments and the promise they hold for lifelong cognitive wellness.
Subject of Research: People
Article Title: Stability of general cognitive ability from infancy to adulthood: A combined twin and genomic investigation
News Publication Date: 19-May-2025
Web References: http://dx.doi.org/10.1073/pnas.2426531122
Keywords: Cognitive function, Genetic variation, Cognitive development, Education, Dizygotic twins, Monozygotic twins
