Recent research on human brain development has shown that spanking and other corporal punishment will have a significant adverse affect on the development of a child's brain and brain function. Whenever a child experiences fear and stress, especially when combined with high emotional confusion or emotional separation from a parent or other caregiver, that child becomes biologically and neuro-chemically alarmed and on high alert.
The human brain consists of four distinct layers, the brain stem, mid-brain, limbic system, and the cortex. The brain stem is responsible for the most primitive functions of the body like breathing, body temperature regulation, and blood pressure. The midbrain, also called diencephalon, is a bit more complex, but still mostly reflexive, and is where a person operates when he or she is in a state of alarm. This is the instinctive "fight or flight" area of the brain and is a non-thinking and non-feeling place. The limbic system is the area responsible for experiencing and expressing emotions. The cortex, especially the pre-frontal cortex, is responsible for thinking, problem-solving, showing judgement and a conscience.
Two other key parts of the brain are the hippocampus, which stores memories, and the amygdala, which is part of the limbic system and determines which part of the brain is activated in a given situation. The hippocampus and amygdala work together to determine which parts of the brain are in charge. At any given moment, one of the three upper levels (midbrain, limbic system or cortex) is in charge based on the decisions of the amygdala and hippocampus.
The brain produces powerful chemicals called hormones. Normal development sees the brain release healthy doses of hormones to help a child learn resilience. During times of fear, however, stress hormones can flood the brain, causing anxiety and panic in the child, meaning he or she is less capable of thinking. During an unhealthy "hormone dump," a child will become hypersensitive and overly-reactive until the hormones dissipate, which may take an hour or as long as a day. Because a child's brain is constantly being wired, high states of alarm can "over-wire" a child's midbrain, making it denser and more dominant than it should be.
During these episodes of fear, the hippocampus stores memories for the purpose of protecting and preparing the child for future incidences. For the rest of the child's life, the memories stored in the hippocampus can trigger the same responses that activates the reflexive midbrain.
Whenever a child is highly fearful or alarmed because a parent or other caregiver is inflicting physical pain (like spanking) combined with unhealthy and out of control emotion, his or her brain development is being adversely impacted. A child with a brain that has been developed in healthy ways can function relatively smoothly, allowing the child calmness to think, emotionally connect, pay attention and grow intellectually.
Withholding discipline is not the answer. Finding healthy ways of effective discipline (limit setting, healthy consequences, making amends, etc.) will help develop a child's brain in healthy fashion.