1.1 First 1000 days
The first 1000 days refers to the time needed for a child to grow from conception to the second birthday. It is a time of rapid change. During this period the architecture of the developing brain is very open to the influence of relationships and experiences (Shonkhoff et al. 2016). Early experiences affect the nature and quality of the brain’s developing architecture by reinforcing some synapses and pruning others through lack of use. The first 1000 days shape the brain’s architecture, but higher-order brain functions continue to develop into adolescence and early adulthood (Kolb, Harker, and Gibb 2017).
The classic nature versus nurture debate contrasts the viewpoints that variation in development is primarily due to either genetic or environmental differences. The current scientific consensus is that both genetic predisposition and ecological differences influence all traits (Rutter 2007). The environment in which a child develops (before and soon after birth) provides experiences that can modify gene activity (Caspi et al. 2010). Negative influences, such as exposure to stressful life circumstances or environmental toxins may leave a chemical signature on the genes, thereby influencing how genes work in that individual.
During the first 1000 days, infants are highly dependent on their caregivers to protect them from adversities and to help them regulate their physiology and behavior. As Figure 1.1 illustrates, caregivers can do this through responsive care, including routines for sleeping and feeding. To reach their developmental potential, children require nutrition, responsive caregiving, opportunities to explore and learn, and protection from environmental threats (Black et al. 2017). Gradually, children build self-regulatory skills that enable them to manage stress as they interact with the world around them (Johnson et al. 2013).