The concept of comfort objects is discovered by the reader in chapter 2. Comfort objects are given to the little children at the Nurturing Center before they turn one year old. All children are born and cared for at the Nurturing Center. When that child turns one, he or she is adopted by a family that has applied for a child and been chosen to receive that child. A one year old child is old enough to recognize faces and voices. Many one year old children have even learned to walk. What I'm trying to say is that the child is "with it" enough to recognize that his or her new family is not the same family that took care of him/her for the past year. It's scary. My own children didn't even like being handed off to grandma when they were one (and they saw her like once a week). Strangers were terrifying.
The comfort object is exactly what it sounds like. It is an object meant to give the one year old some kind of tangible comfort during the adoption process. That's why the object is usually something soft and cuddly (unlike my boys, their comfort objects are Hot Wheels).
Many of the comfort objects, like Lily's, were soft, stuffed, imaginary creatures. Jonas's had been called a bear.
The comfort objects are one of the few instances in the entire novel where the reader sees some emotional softness from the people. Unfortunately, children don't get to keep their comfort object forever. When a child turns eight, the comfort object is taken away and given back to the nurturing center to be used again.
"Lily," her mother said fondly, "you're very dose to being an Eight, and when you're an Eight, your comfort object will be taken away. It will be recycled to the younger children."
Comfort objects help the babies feel safe and secure when they make the transition from the Nurturing Center to their assigned families. All babies age at the same time. In other words, every child born in a year turns “one” at the same time, regardless of when in that year the child was born. At this time they are taken from the Nurturing Center, where they have been raised by Nurturers, and given to a family unit. A mother and father have applied for a child, and they are given a family and a name at the Ceremony of One. The object helps ease the transition, just as our children use stuffed animals and baby blankets to comfort them when they are sad or scared. Comfort objects are taken awhile when the child turns eight.
While in many ways the people in The Giver seem to be very cut off from sentimentality and what they might call frivolous emotions, a bit of the old humanity remains, particularly in regard to the small children. Because of this, a comfort object is given when they leave the Nurturing Center and are placed with a family unit. A significant detail of Gabe's "hippo" is that it is, in fact, an elephant. By introducing the comfort object into the narrative, the author can be seen as showing two important things: the first being that although the adults seem to be removed from feelings of attachment, they still recognize the inherent need for small children to be comforted; the second is that society's memories are void of even a basic knowledge of the biological and ecological diversity of their own history. The "hippo" is a mythical creature to these people that is, in reality, a representation of another animal completely.