According to Bowlby, infants must form an attachment with their caregiver during the critical period which is between three and six months of age. However, Bowlby later acknowledged that infants could form an attachment after this period (up to three years of age); however, he maintained that the successful formation of an attachment would be increasingly difficult after this initial period. Bowlby said that if an attachment didn’t form during this time frame, the child would be damaged for life – socially, emotionally, intellectually and physically.