The Kennard principle states that brain injuries are better sustained early in life due to greater recovery rates in younger individuals.

“So there's actually a principle of biology, not many people know this, it's actually a principle neurology which is called the Kennard principle, which says, if you're going to have a brain injury, you want to have it early in life. And of course better to not have a brain injury at all but if you're going to have it you want to have it early in life. And this is based on a tremendous number of experiments examining the amount of recovery and the rate of recovery in humans that had lesions to their brain either early in life or later in life.”