Later-born children also develop expectations that spark jealousy. Even though they have not received exclusive parental attention, they have enjoyed the special status of being the youngest child in the family and of receiving preferential treatment, because parents tend to give the youngest child the most attention. Thus, regardless of whether an infant is a firstborn or a later-born child, during early infancy he becomes accustomed to being treated as the number one baby. For the number one baby, parental attention toward another baby violates her expectations, which leads to a special kind of frustration, known as jealousy. Anger and jealousy, like all emotions, -don t just snap into place.
Newborns start off capable only of simple feelings of pleasure and pain.
Through increased experience and cognitive maturation, these sensations are elaborated and refined into various distinct emotions. Just as infants do not know how to run without first learning how to sit, stand and walk, they do not instantaneously develop jealousy in the precise moment when a sibling is initially presented. Jealousy emerges through a gradual, though invisible, developmental process in which infants slowly acquire certain kinds of expectations. Through their experiences with parents, infants come to expect parental attention and they expect it to have certain qualities. Happy babies expect it to be plentiful, prompt, predictable and tender.