Harry Harlow in his study The Nature of Love looked at how monkeys reacted in different situations. In his experiments he had baby monkeys in cages with either a cloth monkey that would deliver food to the baby monkey or a wire monkey that would deliver food to the baby monkey. In the study it was found that the monkeys in both cases ate the same amount of food and gained the same amount of weight. However, the monkeys that had the wire monkey mom had problems with digestion and problems with diarrhea. Further, these monkeys were tested by putting them in situations that would frighten them and they would run to the cloth monkey but when the cloth monkey was not around they would freeze.
Another interesting fact that came from this experiment was that when the monkeys were taken away from the cloth monkeys for several days when reunited they would play with the cloth monkey ignoring other objects in the room that the monkey had normally played with.
Harlow points out that the key to successful parenting is contact comfort which means that both parents need to be involved.
In creating our characters we need to understand where our MC get there contact comfort from and explore how this looks in our characters if they have had to much or to little.
Tidbit: I have four wonderful children!