Now consider the situation where an infant does not express anger and has not been frustrated. Jealousy works in much the same way. Frustrated expectations precipitate jealousy just as they might precipitate anger. In the case of jealousy, however, the expectations associated with jealousy are specifically related to what psychoanalysts have named a love object, such as a spouse or parent, and how she gives out attention to other individuals. This holds true for adults as well as infants.
Infant jealousy is usually a response to a parent s directing attention toward a sibling.
Firstborn children are upset by this because they develop the expectation of receiving exclusive parental attention since there are no other children present during the course of the day. 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.