In a paper published in the Journal of Mental Science for July, 1950, I suggested that head-banging originated in the infant's desire to reproduce the thrust of the mother's apex-beat against his head while he was being nursed on her left arm, either as a means of self-comfort or in retaliation for what he had felt to be an attack or as both combined. In the present paper I propose to analyse this infantile experience further, and to trace to some of its component elements certain other peculiarities of childish behaviour.I shall begin by considering the case of a bottle-fed baby, that is to say, one who at every feed is held in his mother's left arm with his right temple against her left breast (and I shall suppose that the mother is not herself a case of dextrocardia.) In addition to the teat in his mouth and the milk being swallowed, such an infant feels the thrust of the mother's apex as a series of taps against his head which tend to impart to the latter a rolling side-to-side movement, he hears her heart-beat as a rhythmic lub-dup, he feels the rise and fall of her chest in respiration as a slower to and fro rocking of his whole body, and he hears the sighing rustle of her breathing beneath his ear. The sound and thrust of the heart-beat are of course louder and stronger at the limit of the mother's expirations, and indeed the tap of the apex may be felt only then. In other words, the suckling hears two separate series of interwoven unsynchronized rhythmic sounds continuing throughout the whole of his feeding times. In addition to all this, he feels the warmth of the maternal body, the steady clasp of the mother's arm, he smells the milk and the woman's body odour (sweaty, or scented by her soap and talcum powder), and lastly, he feels (and may smell) her breath as an intermittent warm breeze on his face and in his hair. The mother seldom speaks while she is feeding her baby, and the room is often quiet, mother and child being alone together. A breast-fed baby also feels smooth warm skin under his fingers, but he has the mother's heart against his head, during only half his feeding times.The other occasions on which a woman commonly holds a child firmly against her breast are, of course, when she is trying to comfort a crying baby, or to restrain a struggling toddler from escaping to some forbidden activity. Here the child is angry and the mother herself often either anxious or angry or both, so that her heartbeat is greatly increased in force, and the furious infant feels it as a series of aggressive blows on his head, each of which is accompanied by a bumping noise.
Williams on Ethics, Knowledge, and Reflection