Recent research from Stanford Medicine challenges the prevailing approach of studying brain function by relying on averaged data from multiple individuals, revealing that this method may obscure vital insights into how individual brains operate, particularly in children facing challenges with goal-directed tasks. This groundbreaking study highlights that the intricate patterns of brain activity in children with varying abilities become apparent only when analyzed on an individual basis rather than through group averages, suggesting profound implications for understanding neurological conditions like attention-deficit/hyperactivity disorder (ADHD).
A focal point of this research is inhibitory cognitive control, a crucial cognitive process that allows the brain to suppress distractions and irrelevant stimuli to maintain focus on a task. By studying more than 4,000 children using functional magnetic resonance imaging (fMRI) while they performed repeated trials of a task designed to measure inhibitory control, researchers unveiled dynamic brain activity patterns unique to each participant. These findings, published in the journal Nature Communications, underscore the importance of personalized analysis in neuroscience, beyond the conventional group-level data interpretations.
The Stanford team was led by Percy Mistry, PhD, a research scholar in psychiatry and behavioral sciences, alongside Nicholas Branigan, MS, specializing in research data analysis. Their collective expertise drove this expansive study, which also benefitted from the guidance of senior author Vinod Menon, PhD, a distinguished professor in psychiatry and behavioral sciences. Together, they explore how individual brains fluctuate dynamically in response to tasks demanding focused cognitive control, revealing nuances that traditional group-based studies cannot capture.
In their methodology, the researchers concentrated on a task known as the “stop-signal task.” This experimental paradigm requires participants to respond swiftly to a “Go” signal by pressing a button but to inhibit that response when an infrequent and unpredictable “Stop” cue follows immediately. This task effectively measures reactive and proactive inhibitory control processes, offering a window into the brain’s ability to regulate behavior under competing demands. While prior studies have averaged brain responses across groups of children, this study uniquely examined temporal fluctuations within each child’s individual trials.
One of the most striking revelations from this analysis was the discovery of opposing patterns between individual and group-level brain activity. In group averages, slower reaction times to the “Go” signal correlated with heightened activation in several brain regions, notably the default mode network—an area commonly associated with internally directed cognition such as daydreaming or self-referential thought. However, when examined within individuals, slower responses coincided with reduced activity in the default mode network, an inversion of the group-level trend that underscores the complexity and variability of brain function.
This unexpected divergence exemplifies Simpson’s paradox, a statistical phenomenon where trends apparent in aggregated data reverse when examined within subgroups or individuals. In this context, it signifies that cognitive control mechanisms, as reflected in brain activity, cannot be fully understood without appreciating the personalized neurocognitive dynamics at play. The implications are profound, suggesting that normative models based on group averaging might misrepresent or oversimplify the neural underpinnings of behavior in developmental populations.
Further analyses revealed that children could be categorized into subgroups based on their cognitive control and performance monitoring, the latter defined as the capacity to adjust behavior after errors. These groups exhibited distinct and often inverse brain activation trajectories, especially in response to repeated exposures in the stop-signal task. Such individualized brain responses indicate that cognitive control is not a monolithic capacity but rather comprises multiple interwoven components whose orchestration varies between individuals, particularly in developmental stages marked by neural plasticity.
The team also deployed mathematical modeling to quantify how children adapted their motor responses over successive trials. Children exhibiting adaptive behavior displayed progressively quicker stopping times with increased anticipation of “Stop” signals. Contrastingly, maladaptive children showed diminishing expectancy, reflecting deficits in performance monitoring. These behavioral adjustments were not just theoretical constructs but were mirrored in distinct patterns of brain regional activity, supporting the notion that cognitive regulation unfolds dynamically and idiosyncratically within the neural architecture.
This research also elaborates on the dual components of cognitive control: proactive control—the anticipatory preparation to inhibit responses—and reactive control—the on-the-fly suppression when a signal demands immediate cessation of action. Functional brain networks underlying these processes differ in their connectivity and activation patterns between children with strong or weak cognitive control. Intriguingly, children with weaker inhibitory control sometimes leverage alternative or compensatory neural circuits to engage proactive strategies, highlighting the brain’s flexibility and the potential for targeted interventions.
The clinical relevance of these findings extends to conditions such as ADHD, bipolar disorder, and addiction where inhibitory control deficits are prominent. By exposing the heterogeneity in how children’s brains execute cognitive control, the study lays a foundation for personalized therapeutic strategies that could help individuals harness specific inhibitory pathways. This nuanced understanding paves the way for educational and clinical methodologies that respect individual neurocognitive diversity rather than relying on generalized averages.
Moreover, this work has broader implications for the trajectory of cognitive neuroscience and psychiatry. It calls upon researchers to reconsider the efficacy of group-based analyses and to adopt paradigms that prioritize intra-individual variability and temporal neurodynamics. Such a shift is crucial to developing real-time interventions and behavioral modifications attuned to the individual’s unique brain activity patterns, acknowledging that behavior regulation is contextual and evolves moment by moment.
Vinod Menon and colleagues advocate for a paradigm shift away from the notion of an “average brain” towards appreciating the singularity of each brain’s engagement with ever-changing environmental demands. Understanding cognitive control as a dynamic interplay of contextual responses rather than a static ability enables a deeper grasp of how attentional and behavioral regulation occur across different ages and clinical populations.
The dataset underpinning this study originates from the Adolescent Brain and Cognitive Development (ABCD) study, one of the largest longitudinal neuroimaging projects tracking brain development from childhood into early adulthood. This resource, hosted in the National Institute of Mental Health Data Archive, provides an unprecedented scale and richness of data allowing such fine-grained examination of individual cognitive trajectories and neural mechanisms.
Supported by an array of federal and institutional grants, including from the National Institutes of Health and the National Science Foundation, this research represents a confluence of cutting-edge computational resources and multidisciplinary expertise from Stanford University. Through advanced imaging analytics and rigorous modeling, these findings mark a transformative step toward individualized neuroscience that can better inform educational strategies and clinical frameworks aimed at optimizing cognitive development.
By revealing that standard group averaging can obscure critical brain-behavior relationships and potentially mislead interpretations, this study reshapes our understanding of neurocognitive dynamics in childhood. It champions an individualized approach that respects the diversity of brain function and adaptation, holding promise for more effective diagnostics and personalized interventions for cognitive and behavioral disorders.
Subject of Research: People
Article Title: Nonergodicity and Simpson’s paradox in neurocognitive dynamics of cognitive control
News Publication Date: 27-Apr-2026
Web References: http://dx.doi.org/10.1038/s41467-026-71404-0
Keywords: Attention deficit hyperactivity disorder, Neuroimaging, Cognitive control, Inhibitory control, Neurocognitive dynamics, Functional magnetic resonance imaging, Stop-signal task, Performance monitoring, Proactive control, Reactive control, Simpson’s paradox, Individual differences
