Deprivation and Disruption

An Interview with Council Member Charles A. Nelson

Abstract: Early deprivation causes serious disruption in the development of brain architecture and in the behaviors related to the affected brain functions. Some brain structures, and the broad categories of development that depend on them, show more "plasticity," or sensitivity to disruption and intervention for longer periods of time, than others. When problems arise, early intervention can help get development back on track. Professor Nelson's research, including his work in Romanian orphanages, demonstrates how new scientific knowledge can lead to better public policy.

Charles A. Nelson is Professor of Pediatrics at Harvard Medical School, Professor of Education and Neuroscienceat Harvard University, and the Richard David Scott Professor of Pediatric Developmental Research at Children's Hospital, Boston (where he also serves as Director of Research at the Developmental Medicine Center). His broad research interests are concerned with how experience affects the brain and brain development. To this end, he conducts research on typically developing children, and children who have experienced early biological adversity (e.g., prematurity) or psychosocial adversity (e.g., those living in institutions in Romania). He earned his B.A. in psychology from McGill University, an M.A. in psychology from the University of Wisconsin, and a Ph.D. in child and developmental psychology from the University of Kansas.

Policy makers can better understand the development of brain architecture if they have a more detailed knowledge of the placticity of the brain. In that regard, what exactly is a "critical" period, and how is it different from a "sensitive" period?

When scientists talk about a critical period, they're usually implying that a specific experience needs to occur at a very specific time, and if it does not, the brain architecture that depends on that experience won't be built. In comparison, when scientists talk about a sensitive period in the development of brain architecture, they imply that so long as the experience occurs in a broad window of time, optimal development can occur; but after that window of time, a particular behavior is harder and harder to acquire, and eventually can become impossible to acquire.

With a critical period, after a very specific time, the door slams shut. With a sensitive period, you can see the door closing slowly and eventually it might close all the way. However, there may still be an opportunity to push the door open a little bit, if you exert enough effort.

Science has shown that there is a lot of plasticity, or ability to change, in brain architecture throughout childhood. This contradicts common misconceptions about brain development in humans. For example, the false belief that brain development as a whole has a critical period and is completely determined -- the door has slammed shut -- by age 3.

For information about commonly used terms in Council publications, see Definitions.