In certain animal species immediate separation of a mother from here young for a brief period after deliver (the sensitive period) may result in aberrant maternal behaviour. In the human, disorders of mothering, including child abuse, increase disproportionately in situations associated with early neonatal separation of mother and infant, such as prematurity. Mothers in the United States who were offered early contact with their premature infants showed differences in attachment behaviour when compared with mothers whose first contact with their infants was three weeks after delivery. Mothers who had one hour of close physical contact with their nude full-term infants within the first two hours after delivery and who had 15 extra hours of contact in the frist three days behaved significantly differently during a physical examination of the infant at one month and one year, and in their speech to their infants at two years, from a control group of mothers who had only routine contact. In a similar study in Guatemala, mothers who had 45 minutes of early extra contact showed significantly more attachment behaviour at the time of the first breast-feeding (12 hours). These and other studies in the human suggest that shortly after birth there is a sensitive period which appears to have long-lasting effects on maternal attachment and which may ultimately affect the development of the child.