We develop the vital bond of attachment between a mother and her child through a smiling response. As a visual stimulus, the smile has acquired its unique configuration primarily through the simple act of tucking in the corners of the mouth. The mouth opens to a certain point and the lips are drawn back, as in the expression of fear, but with the curling of the corners, the character of the expression changes radically. This development, in turn, has led to the possibility of another contrasting facial posture: that of the mouth down. By adopting a line of the mouth that is completely opposite to the smile, it is possible to indicate an anti-smile. Like laughter, 50 also the hostile face has evolved by a pendulum movement from the friendly face.

But there’s more to smiling than a ‘mouth line’. As adults, we can convey our mood with a twist of the mother’s lips, but the baby brings so much more to the battle. When smiling with full intensity, also kicks and waves arms, stretches hands toward stimulus and moves hands, produces babble, tilts head back and chin sticks out, leans trunk forward or twists to side, and exaggerates his breath. His eyes become brighter and may droop slightly; wrinkles appear under or along the eye and sometimes also on the bridge of the nose; the skin fold between the sides of the nose and the side of the mouth is accentuated and the tongue may protrude slightly. The body movements seem to indicate a struggle on the part of the baby to establish contact with the mother. With her clumsy physique, the baby is probably showing us all that remains of the ancient private attachment response.