Grief doesn’t discriminate by age, and infants are no exception. Yes, infants do grieve. Some people may find this surprising, but, it’s true. When infants experience traumatic loss (it doesn’t have to be a death, but any kind of loss of the familiar, safe, comfortable), the way they deal with that loss often manifests in the form of grief.
In the case of adoption, that loss usually shows up as a change in not only the caregiving environment but the caregiver him- or herself. Having gotten accustomed to “the familiar” (be it the face of a loving foster parent, the feel of a particular family dynamic, or the physical space of a caregiver’s home), any change in that familiar routine and those familiar faces can cause an infant to experience honest-to-goodness grief. Because infants are pre-verbal and can’t tell us what they are thinking, this grief looks mainly physical and behavioral.