Harry Harlow received his BA and PhD (1930) in psychology from Stanford University and immediately joined the faculty at the University
of Wisconsin. Within a year, he had established the Psychology Primate Lab, which continued expanding until it joined with the Wisconsin Regional Primate Lab in 1964. Harlow became the director of the merged
research center. Among the scientists to work there was Abraham Maslow, who would later establish the school of humanistic psychology.
The following information about Harry Harlow's surrogate mother experiments has been adapted from the Wikipedia:
Harry Harlow website.
Rhesus monkeys (Macaca mulatta) from Hainan island, China are the most common monkeys used in biomedical research. In his most popularized series of experiments, conducted between 1963 and 1968, Harry
Harlow offered young rhesus monkeys a choice between two surrogate "mothers." In the first group, the terrycloth mother provided no food while the wire mother did, in the form of an attached baby
bottle containing milk. In the second group, the terrycloth mother provided food; the wire mother did not. It was found that the young monkeys clung to the terrycloth mother whether it provided them with
food or not and that the young monkeys chose the wire surrogate only when it provided food. Apparently the terrycloth mothers provided something that was more valuable to the young monkeys than food. She
was providing contact comfort. Harry Harlow's interpretation was that the preference for the terrycloth mother demonstrated the importance of affection and emotional nurturance in mother-child relationships
Whenever a frightening stimulus was brought into the cage the monkeys ran to the cloth mother for protection and comfort no matter which mother provided them with food. This response decreased as the monkeys grew older.
When the monkeys were placed in an unfamiliar room with their cloth surrogates, they clung to it until they felt secure enough to explore. Once they began to explore they would occasionally return to the cloth mother for comfort. Monkeys
placed in an unfamiliar room without their cloth mothers acted very differently. They would freeze in fear and cry, crouch down, or suck their thumbs. Some of the monkeys would even run from object to object, apparently searching for the cloth mother
as they cried and screamed. Monkeys placed in this situation with their wire mothers exhibited the same behaviors that the monkeys with no mother accompanying them did.
Once the monkeys reached an age where they could eat solid foods they were separated from their cloth mothers for 3 days. When they were reunited with their mothers they clung to them and did not venture off to explore as they had in
previous situations. Harry Harlow claimed from this that the need for contact comfort was stronger than the need to explore.
The study also found that monkeys who were raised with either a wire mother or a cloth mother gained weight at the same rate. However, the monkeys that had only a wire mother had trouble digesting the milk and suffered from diarrhea
more frequently. Harlow interpreted this to mean that not having contact comfort was psychologically stressful to the monkeys.
Harlow first reported the results of these experiments in "The nature of love," the title of his address to the sixty-sixth Annual Convention of the American Psychological Association, Washington, D. C., August 31, 1958.
These studies were motivated by John Bowlby's World Health Organization-sponsored study and report, Maternal Care and Mental Health in 1950, in which Bowlby reviewed previous surveys of the effects of institutionalization on child development.
Bowlby's report was quickly recognized by psychologists and policy-makers as an unrivaled contribution to the field of child development. In 1953, his colleague, James Robertson, produced a short and controversial documentary film titled
A Two-Year-Old Goes to Hospital demonstrating the nearly immediate effects of maternal separation. Bowlby's report, coupled with Robertson's film, demonstrated to doctors and psychologists the clear importance of maternal care in humans, just as Dr. Benjamin
Spock's 1946, The Common Sense Book of Baby and Child Care had already done for nearly everyone else, but Bowlby's theoretical conclusions generated much debate.
It was this debate, about the reasons behind the demonstrated and acknowledged need for maternal care, that was addressed by Harlow in his studies with the cloth and wire surrogates.
Later research
From around 1960 onwards, Harlow and his students began publishing their observations on the effects of partial and total social isolation. Partial isolation involved raising monkeys in bare wire cages that allowed them to see, smell, and hear other monkeys,
but provided no opportunity for physical contact. Total social isolation involved rearing monkeys in isolation chambers that precluded any and all contact with other monkeys.
Harlow et al reported that partial isolation resulted in various abnormalities such as blank staring, stereotyped repetitive circling in their cages, and self-mutilation. These monkeys were then observed in various settings. Some of
the monkeys remained in solitary confinement for 15 years. A variation of this housing method, using cages with solid sides as opposed to wire mesh, but retaining the one-cage, one-monkey scheme, remains a common housing practice in primate laboratories
today.
In the total isolation experiments baby monkeys would be left alone for 3, 6, 12, or 24 months of "total social deprivation." This procedure produced monkeys that were severely psychologically disturbed. | 
