Wolf Singer, PAS Academician and Ernst Struengmann Institute for Neuroscience in Cooperation with Max Planck Society, Frankfurt, Germany

1. Introduction

Human beings are born with extraordinary potential, but realizing that potential depends not only on biology but also on its embedding in the material and cultural world. From the very beginning of life, the brain is shaped by a continuous interplay between genetic instructions and the surrounding environment. While much of the body matures in predictable ways, the brain is unique in that it develops itself through learning. It records experiences not in a notebook, but in its very structure – the intricate, ever-changing web of connections among its billions of neurons.

This process of shaping and reshaping the brain’s structure is particularly pronounced during development, which in humans extends until about age 25. This epigenetic shaping of brain architecture allows us to adapt to the environment’s specific demands, learn languages, form relationships, and master skills. However, this plasticity also comes with a price: the brain is not only open to enrichment but also vulnerable to harm and deprivation. The more plastic a system, the more its eventual shape depends on the conditions under which it develops. In children and adolescents, the brain is at its most plastic state. It is during these early phases of life that we form the mental models that govern our behavior. The architecture of the brain is not only responsible for perception, memory, and reasoning but also for the formation of moral judgment, social interaction, and emotional self-regulation. It is the substrate of our identity. Crucially, it is not set in stone by our genes. While genetic programs provide a basic scaffold, it is experience – what we see, hear, touch, and do – that determines the final form.

This makes the early years – especially childhood and adolescence – a time of both great opportunity and great risk. Every interaction, every stimulus, and every absence of experience contributes to the shaping of brain architectures and ultimately determines what kind of person a child becomes. It is during these years that fundamental capacities are established: perception, language, emotional regulation, decision-making, moral judgment, and social competence. These are not traits we simply “grow into.” They emerge from complex patterns of neural activity that gradually stabilize over time.

Yet, the environment in which today’s children grow up is radically different from that of any previous generation. Digital media, smartphones, social networks, and algorithmically curated content play an increasingly central role in how young people experience the world. These technologies are not neutral; they compete for attention, mediate relationships, and shape behavior in subtle but powerful ways. For a brain that is still under construction, this new digital environment can act as a scaffold or a constraint. The critical question we must ask is: are we providing the right kinds of experiences to support healthy brain development?

The challenge is that brain development is largely invisible. A child who spends hours with a screen may seem quiet and content. However, beneath the surface, neural networks are adapting to that experience. They are being tuned to the patterns of stimulation they receive, while other, potentially more valuable pathways may remain underdeveloped. The effects may not be immediately obvious, but their consequences can last a lifetime.

Understanding this process is not just a scientific concern; it is a societal responsibility. If we wish to guide the development of young minds wisely, we must first understand the forces that shape them. This includes not only biology but also technology, culture, and education. Only by recognizing the brain as a system that builds itself through experience can we begin to evaluate which kinds of environments support and which may hinder the growth of capable, resilient, and empathetic individuals.

In the following sections, we will explore what neuroscience has discovered about how the brain develops, why certain periods are especially sensitive, how experience shapes its internal architecture, and what the rise of digital media means for the next generation. This understanding is essential for parents, educators, policymakers, and all who care about the well-being of children in the 21st century.

2. The Functional Architecture of the Brain

The brain does not operate as a collection of isolated parts. It is a network – a dynamic and hierarchically organized system of interconnected regions, each contributing to the integrated whole of perception, action, and thought. This network is what I refer to as the brain’s functional architecture, and understanding how it is formed is essential to understanding brain functions and ultimately ourselves.

This architecture is both the product of evolution and the imprint of experience. Genes provide the basic scaffolding, determining the general layout: where different processing modules reside, how they are initially connected, and what kinds of neurons populate them. This inherited structure reflects the accumulated knowledge of our species, honed by millions of years of natural selection. It enables newborns to respond to their environment in meaningful ways from the outset. However, it is not complete; it is a first draft.

What transforms this draft into a functioning adult brain is the experience-dependent refinement of connections. As the child interacts with the world, neural activity shapes the architecture by reinforcing some pathways and weakening others. This process is not random; it follows clear principles: neurons that are activated together tend to connect more strongly – “neurons that fire together wire together.” In this way, the brain becomes a record of experience, a biological memory of the world as it is encountered and understood by the individual.

The cortex, the outer layer of the brain responsible for higher cognitive and executive functions, is a particularly striking example. Despite serving diverse tasks – vision, language, planning, reasoning, and remembering – its regions are constructed according to a shared blueprint. Each area consists of circuits that are canonically structured, but their specific functions are defined by their input and output connections. This means that the same basic module can evolve into a center for face recognition in one region and into a control unit for voluntary movement in another, depending on how it is wired.

Furthermore, these cortical modules are embedded in a dense mesh of reciprocal connections. They continuously communicate with one another, exchanging signals in real time. This reciprocity enables the brain to function not as a collection of discrete processors, but as a coherent system. What we call perception, for instance, is never a simple registration of sensory input. It is an interpretation shaped by prior knowledge stored in the architecture itself.

This brings us to a fundamental insight: all knowledge and all capacity for reasoning or judgment reside in the structure of connections between neurons. There is no separate “seat” of thought apart from the network. Cognition emerges from the architecture, which is shaped by both inheritance and experience.

In practical terms, this means that development is not merely about adding new content to a finished machine. It involves building the machine itself. The child’s brain is under construction, its wiring still flexible, and its modules still awaiting assignment. This flexibility is a strength – it allows for learning and adaptation – but it also presents a vulnerability. Experiences that are rich, coherent, and emotionally meaningful will shape a brain better equipped to understand and engage with the world. Conversely, experiences that are fragmented, superficial, or disconnected from bodily action may lead to architectures that are less well-tuned for the complexities of real life.

In the sections that follow, I will explore how this architectural development unfolds over time, what makes certain phases particularly sensitive, and why the type of experience, not just its content, matters so deeply for the growing mind.

3. Critical Periods – Windows of Irreversible Change

The development of the brain does not proceed in a smooth, linear fashion. Instead, it unfolds through a sequence of biologically timed windows known as critical periods. During these phases, the brain exhibits an exceptional degree of plasticity – an increased capacity to form and refine connections in response to experience. These are the moments when external input has the greatest power to shape internal structure.

Critical periods begin early in life and extend into the third decade, with various functions maturing at different times. Basic sensory systems, such as vision, hearing, and tactile sensation, are the first to develop. This is why infants must be exposed to light and sound from the beginning – without it, the circuits for seeing and hearing fail to form properly. As development progresses, more complex functions emerge: sensory-motor coordination during early childhood, language acquisition, spatial orientation, emotional regulation, and, later, the social and executive abilities that characterize adolescence.

Each of these functions has its own sensitive phase during which the underlying neural circuits are particularly malleable and can be refined, stabilized, or removed. If experience during these phases is lacking, disordered, or misaligned with the brain’s expectations, the result can be a permanent loss or an abnormal layout of connections, leading to dramatic consequences for the respective functions. Once the critical period of a particular area of the brain closes, the changes become irreversible. There is no further outgrowth of connections, nor is it possible to physically remove dysfunctional connections. A striking example comes from studies of visual development: if one eye is deprived of input during the critical period, even temporarily, the brain may reorganize itself so that the eye never fully recovers, despite being structurally intact. The neural connections that would have processed signals from that eye have been reassigned or eliminated. The system has moved on.

These windows of plasticity are marked by intense growth followed by pruning. In early development, the brain overproduces connections, exploring a vast range of possibilities. Later, it eliminates those that are not reinforced by experience. This pruning process is not a loss but rather a refinement – like a sculptor removing what is unnecessary to reveal form. However, once the sculpture is set, it cannot easily be reshaped. This is why we say that the changes that occur during critical periods are, in many cases, irreversible.

Importantly, the sequence of these critical periods follows a progression from lower to higher functions. This indicates that early experiences establish the foundation for later capacities. A child who lacks rich sensory input may struggle later with language. A teenager deprived of meaningful social interaction may find it more difficult to develop empathy or a stable sense of self. These are not merely psychological observations – they reflect the logic of neurodevelopment.

Adolescence, in particular, is a phase of significant reorganization. The brain transitions from an overconnected system with a relatively flat hierarchy to one where central hubs, such as the prefrontal cortex, take control over behavior and decision-making. This transition underlies the development of self-regulation, abstract thinking, and moral reasoning. It is also a time of vulnerability when the balance between different networks is delicate and still in flux. The groundwork laid earlier in life must now be integrated into a coherent system.

Because of this, the quality of experience during critical periods is not just important – it is decisive. The brain cannot simply be “updated” later if these windows are missed or filled with impoverished input. What is built during these years will, to a large extent, define the adult mind.

In the next section, we will examine more closely the types of experiences the brain needs to mature properly and the reasons why passive exposure is insufficient.

4. Experience as the Architect – Why Active Engagement Matters

If the brain is shaped by experience, then the nature of that experience matters deeply. It is not sufficient for the senses to be stimulated. What is important is how the individual engages with the environment – whether passively or actively, superficially or in depth, with or without purpose. In both the laboratory and daily life, we find repeatedly that only active, self-directed interaction leads to the kind of neural activity that refines and stabilizes the brain’s architecture.

This distinction is perhaps best illustrated by a classic experiment in developmental neuroscience: the kitten carousel, introduced by Held and Hein from MIT. In this setup, two young cats are exposed to the same visual environment but in radically different ways. The carousel includes two connected gondolas for the kittens. One kitten can touch the ground and explore the space through its own movements, while the other is passively carried, seeing the same sights but lacking the ability to act. When later tested, only the active kitten develops normal depth perception and visuo-motor coordination. The passive one, despite receiving identical sensory input, fails to build the necessary neural circuits. The difference lies not in what they saw, but in how they experienced it.

This principle – active engagement as a prerequisite for learning – is not limited to motor skills or perception; it applies just as much to the development of higher cognitive functions. Attention, motivation, and emotional investment all serve as gates for plasticity, determining whether experience leaves a mark on the brain. A child who passively listens to language will not learn to speak with the same fluency as one who engages in dialogue. A teenager scrolling through images may not form the same emotional insights as one who navigates complex relationships face-to-face.

The mechanisms behind this are now well understood. Synaptic changes, which form the basis of learning and memory, depend on the coordinated firing of neurons. For this to occur effectively, the brain must be in a state of readiness: alert, interested, and actively processing information. Passive exposure does not consistently create the neural conditions required for such change. While it may generate fleeting impressions, it does not build lasting structures.

This has important consequences in the context of digital media. Many forms of screen-based interaction are designed for ease and efficiency. Algorithms anticipate user preferences, reducing the need for exploration. Interfaces flatten complexity. Virtual environments often separate action from consequence and observation from physical feedback.

While there are certainly interactive and educational uses of technology, much of it promotes a mode of engagement that is receptive rather than generative.

Of course, not all passive experiences lack value. We learn from listening, reading, and observing others. However, even in this context, the distinction between active and passive is not absolute. A child who listens to a story and imagines its characters is not passive in the neurological sense. Their brain is engaged, drawing on memory, emotion, and prediction. What matters is the degree of mental activity – the extent to which the experience demands interpretation, response, and connection to the self.

Ultimately, the brain selects the signals it needs for its maturation. It does not indiscriminately absorb all input. It relies on attention to filter what matters and on movement and interaction to test what is learned. This is how the functional architecture becomes adapted to the real world: through a process of inquiry, feedback, and embodied experience.

As we shall see in the next section, adolescence represents a particularly delicate phase in this process. The need for meaningful, engaged experience is never greater – and the risks of misalignment never more serious.

5. Adolescence – A Fragile Phase of Reorganization

Adolescence is often described in psychological terms as a time of identity formation, emotional volatility, and growing independence. From a neurobiological perspective, it encompasses all of these aspects – and more. It represents a phase of radical reorganization in the brain’s functional architecture, building on what came before and setting the stage for adult cognition and behavior. However, it is also a period of particular vulnerability when the balance between flexibility and stability becomes delicate.

During this stage, the brain’s functional organization undergoes a large-scale restructuring. During childhood, functional networks are organized in a relatively flat manner. In adolescence, this configuration shifts toward a more centralized architecture. Hubs begin to emerge – regions such as the prefrontal cortex assume greater control, integrating information across distant areas and coordinating complex behaviors. This shift enables higher-order functions like impulse control, planning, abstract thinking, and moral reasoning. In a sense, adolescence is when the brain learns to govern itself.

However, this transformation is not smooth. It relies on the timely strengthening of connections, particularly long-range projections between brain regions. These pathways are sensitive to activity-dependent processes and require repeated, meaningful use to consolidate. If these connections are underused or misaligned with the demands of the environment, they may not form as robustly, leaving the system less integrated and more susceptible to dysfunction.

One of the hallmarks of this phase is the transient instability of neural coordination. Research has shown that the synchronization of brain activity – what we call phase locking – temporarily becomes disrupted during early adolescence. This temporary loss of coherence may explain some of the mood swings, impulsivity, and cognitive lapses often associated with this period. It is as though the brain is recalibrating, shedding inefficient patterns and testing new configurations before settling into its mature form.

This reorganization also marks a period when certain neuropsychiatric conditions can begin to manifest. The onset of schizophrenia, for example, typically occurs in late adolescence or early adulthood. While the precise causes remain unclear, the timing suggests a link with the closing stages of neural development – particularly the refinement of long-range connections and the establishment of self-monitoring functions in the prefrontal cortex. It serves as a stark reminder that development does not guarantee successful maturation; instead, it must be supported both biologically and environmentally.

In this context, the role of experience becomes critical once again. Freud called this period “the second chance.” Adolescents need opportunities to test themselves in real-world settings – to negotiate relationships, confront challenges, explore ideals, and deal with consequences. These experiences are not simply shaping social or moral norms deposited in memory; they structure the functional architecture of the brain and contribute to the stabilization of new configurations. Without them, development may stall or deviate.

The risk posed by digital media is that they might substitute for these experiences rather than support them. Virtual interactions often lack the richness and immediacy of face-to-face contact. If the adolescent brain practices control and empathy less frequently, or in oversimplified contexts, the circuits supporting these functions may remain underdeveloped.

To guide this phase well, we must acknowledge its biological foundations. Adolescence is not just a turbulent stage to be endured. It is a fragile and essential process of integration. What is rehearsed during these years is rehearsed for life.

In the final section, we will turn to the questions that arise when the developmental blueprint of the brain is increasingly shaped by digital environments – and what this might mean for future generations.

6. Digital Media and Virtual Environments – The Big Questions

We are experiencing a transformation in the developmental environment. For children and adolescents today, digital media are no longer occasional tools but constant companions. They shape communication, define play, mediate learning, and increasingly substitute for real-world interaction. In light of what we know about how the brain develops – how it depends on rich, embodied, and actively engaged experience – this shift raises urgent questions.

The developing brain is exquisitely sensitive to the type of input it receives. It constructs its internal models of the world based on experience: from what it hears and sees, from what it touches and moves through, and from what it does. When that experience is passive or abstracted from bodily action, key developmental mechanisms may not be properly engaged. When it is dominated by algorithmically curated content, the opportunity for exploration and self-directed learning can be limited. When social interactions occur largely through screens, emotional feedback may be dulled, nonverbal subtleties lost, and the essential training of empathy and cooperation weakened.

These concerns are not rooted in nostalgia for a pre-digital world; they are grounded in neuroscience. We know that the brain’s architecture is shaped by activity and that critical periods exist during which the foundations of perception, reasoning, and social understanding are laid. We understand that these periods are sensitive to deprivation – not only of stimulation but also of meaningful engagement. Additionally, we know that adolescence represents a turning point, when the brain must integrate earlier experiences into a coherent whole. The timing of these processes is not negotiable; what is missed cannot simply be reintroduced later.

The key distinction is not between “digital” and “analog,” but between passive and active, between external noise and internal structure-building. A digital environment that encourages exploration, challenges assumptions, fosters dialogue, and supports emotional engagement can effectively promote development. Conversely, one that rewards distraction, minimizes effort, and replaces human presence with artificial feedback may not.

This does not mean that all exposure to digital media is harmful, or that children must be shielded from modern tools. Rather, it emphasizes the need to be intentional in how these tools are integrated into young lives. We must ask: Does this interaction invite curiosity? Does it require agency? Does it connect to the body, to emotion, to others? Is it shaping a brain that is capable of navigating the complexities of the real world?

As a society, we have not yet answered these questions. However, neuroscience has provided us with the tools to explore them effectively. We understand more than ever how the brain develops and why the early years of life are so profoundly significant. What remains is to apply this knowledge – to recognize that the environment we create for the next generation is not merely a background to their lives. It shapes the architecture of their minds.

Further reading:

The publication cited below is a review published in the Reports of the Ernst Strüngmann Forum that contains references to research papers supporting the claims made in this contribution.

Wolf Singer, “The role of oscillations and synchrony in the development of the nervous system” (2018) in Emergent Brain Dynamics; Prebirth to Adolescence. Eds. April A. Benasich and Urs Ribary, The MIT Press, 2018 ISBN 9780262038638. DOI: https://doi.org/10.7551/mitpress/11957.001.0001. ISBN electronic: 9780262348591. The chapters of the book can be downloaded from the Home Page of the Forum: esforum.de