If an infant does not express jealousy and has not been exposed to a jealousy-inducing event, do not assume that jealousy is nonexistent in that infant. If parents wish to know the status of their infant’s jealousy development, they do not need to await the day they confront him with his newborn baby sister or brother. All they have to do is set up a situation that triggers jealousy by violating their infants’ expectations of receiving preferential treatment.
From Preventing Sibling Rivalry by Sybil Hart, PhD
Myth Number Two
Sibling Rivalry Is Caused by Changes in Routine and Underpreparation
The arrival of a newborn baby coincides with other changes in family life. Sometimes the changes are so numerous they appear to be overwhelming, especially to a toddler. Baby paraphernalia, old, borrowed and bought, accumulate from various sources and are amassed in heaps all over the house. The assemblage might include a bassinet, baby bathtubs, playpens, bottles, cans of formula, boxes and jars of baby food, intercom systems, cameras, video recorders, different kinds of film, photo albums, strollers, walkers, swing sets, cradles and other rocking devices, various infant carriers to strap into a car or a stroller or onto an adult, mountains of disposable diapers, sheets, wipes, pacifiers, nipples, teething rings, baby soaps, lotions, oils and ointments, stuffed animals, toys, games, wall hangings, frescoes, mobiles, audiotapes with songs, videotapes with movies and clothing that will not fit or be appropriate for years to come.