A Dependency need is characterized by two components: (1) It is a real need of the organism, something that must be present for the human being to thrive. (2) It is something that individuals cannot provide for themselves. An infant has very many dependency needs. Some are obvious, and some have only come to the attention of researchers as the result of epidemiological studies. It is very well known that infants must be adequately fed, provided with adequate water, kept within a narrow range of temperature, cleaned, etc. It was not well known until the middle of the twentieth century that infants also need the presence of warmth and the texture of skin or fur. In other words, infants need something that is usually called "maternal warmth" even though males and even members of other species can provide it. The phenomenon was first noticed when researchers learned of the higher mortality rates for infants maintained in orphanages. When the obvious factors such as inadequate nutrition, contagious diseases, etc., were ruled out, researchers discovered that mortality rates could be greatly ameliorated by having the nurses in charge of these infants cuddle them in a way that approximated the amount of cuddling infants would normally receive from their own parents.

One classic study involved groups of monkeys that were removed from their mothers during early infancy. The members of one group were maintained in warmed sterile cages and fed from a rubber nipple that was readily available to them. A second group was provided with a maternal figure made of wire mesh, with the nipple in the appropriate position on the figure's body. A third group was provided with a similar mock-up of a mother monkey, but the model was covered with manmade fur. The survival rates and eventual adult levels of social competency varied according to how well the experimental devices provided for the dependency needs of the infant monkeys.

citations from Scientific American articles to follow.