Dr. Greene's Answer
Many theories have been put forward to explain this common behavior. Perhaps the rocking and even the head-banging provide a form of pleasure related to the movement. This joy in movement is called our kinesthetic drive. All infants are rocked by their mothers when they are carried about in utero. Later on, they enjoy being held and rocked in parents’ arms. Movement activities continue as kids grow: the pleasure of jump rope, swings, slides, amusement park rides (bumper cars!) and dancing. These activities all engage the vestibular system of the brain. The amount and type of movement that provides pleasure varies from child to child.
Kids who are understimulated (those who are blind, deaf, bored, or lonely) head bang for stimulation. But children who are overstimulated (in an overwhelming environment) find these rhythmic movements soothing.
For some children, head-banging is a way to release tension and prepare for sleep. Some kids head-bang for relief when they are teething or have an ear infection (Primary Pediatric Care, Mosby 1992). Some kids bang their heads out of frustration or anger, as in a temper tantrum. Head-banging is an effective attention-seeking maneuver.
The more reaction children get from parents or other adults, the more likely they are to continue this habit. Generally, healthy children do not head-bang in order to injure themselves.