Once in place, a defense mechanism such as tuning out takes on a life of its own. Little or nothing of a distressing nature need be there in the immediate environment for it to happen. It becomes, as it were, the “default” setting in the cerebral apparatus of awareness: unless some other special switch is turned on, tuned out will be the state that the brain automatically returns to. Because tuning out is based on deeply entrenched neurological responses, their later activation requires very little stimulus.
