A six-year-old boy that has been an only child until three months ago has had his parents’ undivided attention for six years; and now he has to share that attention with an intruder. To make matters worse, the new sibling is getting more attention than he is (in his perception, anyway). He has made the connection of diapers, bottles, and generally being helpless to getting parents’ attention and he is probably trying to use that to regain the attention that he lost. Both parents need to spend lots of one-on-one time with him, together or one at a time, in activities that are appropriate to his age – playing board games, trips to the movies or zoo, etc. without the baby around. Reassure him that he can do these activities because he is a “big boy” and babies can’t, for example, “Big boys can go to the movies but babies can’t because they might cry during the movie and have to leave.” With continuous reassurance that he is a “big boy” and enough parental attention, the infantile behavior should stop.