By Bruce D. Perry, M.D., Ph.D.


We are time-bound creatures. We have a beginning and an end. Within these boundaries, time passes at a constant rate — the hour of our birth is as long as the hour of our death. Yet while time is constant, we are not. Hours in infancy have more power to shape us than months in middle age. The relative impact of time — time lost or time invested — is greatest early in life. Indeed, humanity was created in childhood.

This is so because of biological relativity. In brief, a biological system is influenced by any experience (a time-limited event) relative to the rate of change in that system. The power of time and experience, therefore, is increased in rapidly changing systems. For humans, the greatest rate of change is during development and, of all of the body's systems, the most dynamic, complex and rapidly changing is the brain. This remarkable organ is comprised of 100 billion neurons, each forming up to hundreds of synaptic connections with other neurons. Chains of neurons form complex functional networks that, ultimately, allow us to walk, talk and think — to create, laugh, love — to envy, hate, and even kill. The properties of the human brain allow us humanity.

Democratic government, complex economies, astounding technologies and social justice are not inevitable genetic manifestations of the human brain; rather they are the distilled products of thousands of generations of experience. The brain has the amazing capacity to store, categorize, process, modify and pass elements from experience to the next generation. It is in this sociocultural distillate — the collective memory of family, community and culture — that an individual child grows. And it is the developing brain's malleability that allows the experiences of many generations to be absorbed in a single lifetime. Yet this capacity to absorb the sociocultural distillate of the family and community decreases during the life span. The relative impact of experience on the individual, and thereby, on society, is greatest in early childhood.

In childhood, time and experience are magnified, amplified and empowered by the opportunity to express our genetic potential — or not. The young child's undeveloped brain organizes in a "use-dependent" way, mirroring the pattern, timing, nature, frequency, and quality of experience. By age three, the brain is 90 percent adult size and the emotional, behavioral, cognitive and social foundation for the rest of life is in place. During early childhood, the organizing neural networks that are developing require touch, sight, sound, smell and movement in order to develop normally. Absent experiences of sufficient duration or quality, some of the genetic potential of the individual will be lost. An infant born in a hunter-gatherer clan 20,000 years ago had the genetic potential to read and write, to play piano, use a joy-stick and understand the double-helix of DNA. Instead, he learned to distinguish between two- and five-day-old antelope tracks, to throw a stick with incredible precision, to read the visual-spatial cues of terrain.

In another example, even Mozart could not have composed had he never heard music. More important, Mozart could not have composed had he never heard music in the first years of his life. Our hunter-gatherer infant would transition to the modern world with no problem, while the hunter-gatherer adult would never make the adjustment. Once developed — once organized — the brain is much harder to modify. At birth, we have a broad potential. For the next few years this potential is narrowed, focused and refined so that the brain expresses the capabilities that are most adaptive for the environment it has perceived. Childhood experiences, therefore, create the person. These organizing childhood experiences can be consistent, nurturing, structured and enriched, resulting in flexible, responsible, empathic and creative adults. Conversely, neglect, chaos, violence and threat create impulsive, aggressive, remorseless and anti-social individuals.

An appreciation of biological relativity and the crucial organizing power of childhood experience have never been more important to our species. Human groups — family, clan, society — are, after all, dynamic interdependent biological units. The rate of change in these groups has been increasing dramatically. Indeed, sociocultural evolution has been accelerating so fast that humankind has changed more in the last two thousand years than in the previous 90,000 — and more in the last two hundred years than in the previous two thousand. Humankind now lives in such a dynamic, human-modified world that in some areas (e.g., transportation, and communications) more change takes place in a single lifetime than in the previous thousand generations! We are now more vulnerable to time.

The implications of this are sobering. We are changing so rapidly that the structures of our families, social systems and communities are not stable from generation to generation. At the same time, the collective experience of our culture(s), the sociocultural distillate, carried in the myths, values, belief systems, child-rearing practices, language, literature, laws, history, arts and science are expanding explosively. Our modern society must face the difficult choices of what we value and pass on. What elements of our history (social or military), what language we speak in schools (Spanish or English), what belief systems (lying is ok sometimes), what skills (football or dance) — what is so important that we mandate instruction (driving a car or child rearing). And more important, how do we divide these responsibilities among the adults in a child's life — parents, grandparents, neighbors, childcare workers, teachers. How should our modern society create and support stable systems to protect, nurture, educate, and enrich our children? More than anything, we must recognize that early childhood is not a passive time. It is, in fact, the most crucial time in the life of an individual — and, thereby, in the life of a society. This generation must understand biological relativism and its most obvious message: to improve society, improve the lives of children.

Time is short. Our world is rapidly changing. Thoughtful dialogue about our society's values, beliefs and child-rearing practices must take place now. The choices we make will have profound impact on the trajectory of our society — and our species. If we choose well, untapped potentials will emerge. If we remain passive and let the momentum of our dissolving social structures sweep us into the next generation, we lose the creativity and productivity of millions of children. And we lose our future.

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Dr. Bruce D. Perry, M.D., Ph.D., is an internationally recognized authority on brain development and children in crisis. Dr. Perry leads the ChildTrauma Academy, a pioneering center providing service, research and training in the area of child maltreatment ( In addition he is the Medical Director for Provincial Programs in Children's Mental Health for Alberta, Canada. Dr. Perry served as consultant on many high-profile incidents involving traumatized children, including the Columbine High School shootings in Littleton, Colorado; the Oklahoma City Bombing; and the Branch Davidian siege. His clinical research and practice focuses on traumatized children-examining the long-term effects of trauma in children, adolescents and adults. Dr. Perry's work has been instrumental in describing how traumatic events in childhood change the biology of the brain. The author of more than 200 journal articles, book chapters, and scientific proceedings and is the recipient of a variety of professional awards.