Harlow's Experiment Summary

Harlow was researching the primates at the Henry Vilas Zoo, to study learning and memory in monkeys. While doing this Harlow discovered something very interesting, the monkeys were starting to develop strategies for Harlow’s tests that he set up. They were known as ‘learning sets’ but then later to be said as ‘Learning to learn’.
To further this development, Harlow was in need of regular access to infant primates. He then thought breeding his own colony of Rhesus monkeys in the year 1932. To help the studies Harlow decided to hand rear the infants in a nursery setting, where he would separate the infants from their mothers 12 hours after birth and place them in wire cages on their own with a cloth on the floor.
While caring for the infant monkeys, Harlow was intrigued as to why every time they took the cloth away to give them a clean one, they would cry and through a fit. In human infants we would call this behaviour a tantrum. They often cling on to the cloth with their little hands as hard as they could and while sleeping they would cuddle up to it. Most scientists didn't pay much attention to this, they would say that it's because of reduction of food, that if they could feed like they would of a mother, the infant would be satisfied. Harlow did not accept this answer and was rather intrigued with what he could find about this matter.
The scientist learned to hand rear the infants properly, but when they were with other infants, they huddled in a corner while clinging to the cloth, the infants were unable to socialise.
With this as inspiration, Harlow wanted to test the ‘bonds between mother and child’. In those days scientists were to believe that if you fussed over your child to much that it would become spoilt. It was a big thing to neglect your Child’s cries unless for feeding or changing. With the infant monkeys, Harlow wanted to prove this theory wrong, that babies do need nurturing to develop better in life, that they need the bond between mother and
child.
To begin the tests Harlow invented what he called a surrogate mother. Separated from their mother about 12 hours after birth, the infant monkeys were raised with a surrogate mother. Harlow tried 2 different types of ‘mother’; Wire mother who was made completely out of wire with a nipple so the infant monkeys can feed, the other was a ‘cloth mother’ made with wood wrapped with cloth. Both surrogate mothers were equipped with a light bulb to keep the infants warm by imitating the warmth from a real mother.
Eventually the infant ran and clung to the ‘cloth mother’. Thinking that the infant would let go when it is hungry, the scientists observed the infant for hours to notice that when the infant became hungry it would hang on to the ‘cloth mother’ and reach over to the ‘wire mother’ to feed. It would repeat this actions several times.
While Harlow was undergoing all this research, he noticed that the infants who were being raised by a wire mothers were having difficulties in digesting the milk. Although the cloth surrogate infant was gaining the same weight as the wire surrogate infant, the wire mother infants were having constant diarrhea.
Harlow's interpretation on this particular behavior was that the lack of contact and comfort was psychologically impacting on their stress levels which was effecting their digestive system.