The Critical Window for Development
Brains develop in early childhood. Construction of the brain begins at conception and by the 1001st day, or the baby’s second birthday, the brain has reached 80% of its adult size. The quality of relationships and experiences during this critical period establishes either a sturdy or fragile foundation for all of the learning, health and behavior that follow.
The most rapid development occurs in the first 1,000 days of life – a critical window for learning to see, talk, walk and think. Development can occur later but with much more difficulty. One in 4 young children live in poverty—growing up with poorer nutrition, and exposed to fewer colors, experiences, relationships that “grow” the brain. Studies show that children in poverty are to 30 million fewer words than children from professional families, which is later reflected in lower fourth grade reading levels. The best chance to close the gap is during the first 1,000 critical days with a loving, adult who cares for the baby, talks, reads, provides the foundation for academic success.
Toxic stress damages the developing brain, which can lead to life-long physical and mental health problems. Scientists now know that chronic, unrelenting stress in early childhood, caused by severe neglect, exposure to violence, or repeated abuse can be toxic to the developing brain.
Nurturing relationships can buffer the effects of early adversity. Absence of a nurturing adult makes “tolerable” stress become “toxic” over time; however, babies can overcome early adversities with a nurturing caregiver.
The brain’s capacity for change decreases with age. Interventions at age 10 won’t have nearly the impact they would have at age 2. The brain is most “plastic” or open to change early in life than after brain circuitry is hardwired in adulthood.
Capacities developed in early childhood are prerequisites for later success. The emotional and physical health, social skills, and cognitive-linguistic capacities that emerge in the early years are critical for success in school and later in the workplace and community.
 INBRIEF: The Science of Early Brain Development, Centering on the Developing Child, Harvard University (www.developingchild.harvard.edu).