ABSTRACT
There is general agreement that injury to the brain in infancy has different consequences than similar injury in adulthood. In fact, this difference was noted as long ago as 1965 by Broca. However, no uniform agreement exists on how or why the consequences are different in infancy and adulthood. One of the most common views on the effects of early brain injury has come to be known as the Kennard Principle. Beginning in the 1930s, Margaret Kennard studied the effects of motor cortex lesions in monkeys. She reported that infant monkeys appeared to have a better behavioral outcome than adult monkeys with similar injuries (Kennard, 1938, 1940). Later, Hans-Leukas Teuber concluded from Kennard’s results that if you are going to have brain damage, have it early, which is what Teuber dubbed the Kennard Principle. The Kennard Principle has some intuitive appeal because it is a common observation that infants seem to recover quickly from many maladies. Because the infant brain is developing, it seems reasonable that it would compensate better than the adult brain. In fact, it is rare for children to experience lasting aphasia, which is a major problem for adults with left-hemisphere injuries. Various authors have used this observation as evidence for plasticity in the infant brain (e.g., Lenneberg, 1967).
