Harry Harlow

Overview
Harry Frederick Harlow (October 31, 1905–December 6, 1981) was an American psychologist best known for his maternal-deprivation and social isolation experiments on rhesus monkeys, which demonstrated the importance of care-giving and companionship in the early stages of primate development. He conducted most of his research at the University of Wisconsin-Madison, where he worked for a time with humanistic psychologist Abraham Maslow.

Some of Harlow's experiments involved rearing infant macaques in isolation chambers that prevented them from having any contact with other monkeys or human beings. The monkeys were left alone for up to 24 months, and emerged severely disturbed.

The experiments were controversial, with some researchers citing them as factors in the rise of the animal liberation movement. William Mason, who worked with Harlow, told writer Deborah Blum that Harlow "kept this going to the point where it was clear to many people that the work was really violating ordinary sensibilities, that anybody with respect for life or people would find this offensive. It's as if he sat down and said, 'I'm only going to be around another ten years. What I'd like to do, then, is leave a great big mess behind.' If that was his aim, he did a perfect job."

Education and career
Born Harry Israel on Halloween night, he changed his name to Harry Harlow in 1930. He earned his B.A. and Ph.D. from Stanford University, and did his research primarily at the University of Wisconsin-Madison where he worked for a time with humanistic psychologist Abraham Maslow.

Early papers

 * The effect of large cortical lesions on learned behavior in monkeys. Science. 1950.
 * Retention of delayed responses and proficiency in oddity problems by monkeys with preoccipital ablations. Am J Psychol. 1951.
 * Discrimination learning by normal and brain operated monkeys. J Genet Psychol. 1952.
 * Incentive size, food deprivation, and food preference. J Comp Physiol Psychol. 1953.
 * Effect of cortical implantation of radioactive cobalt on learned behavior of rhesus monkeys. J Comp Physiol Psychol. 1955.
 * The effects of repeated doses of total-body x radiation on motivation and learning in rhesus monkeys. J Comp Physiol Psychol. 1956.

Surrogate mother experiment


In a well-known series of experiments conducted between 1963 and 1968, Harlow removed baby rhesus monkeys from their mothers, and offered them a choice between two surrogate "mothers," one made of terrycloth, the other of wire.

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.

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 behavior as the monkeys with no mother.

Once the monkeys reached an age where they could eat solid foods, they were separated from their cloth mothers for three 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. Harlow claimed from this that the need for contact comfort was stronger than the need to explore.

The study 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.

Critics of Harlow's claims have observed that clinging is a matter of survival in young rhesus monkeys, but not in humans, and have suggested that his conclusions, when applied to humans, overestimated the importance of contact comfort and underestimated the importance of nursing.

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. The 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 such as René Spitz's and conducted his own surveys on children raised in a variety of settings. In 1953, his colleague, James Robertson, produced a short and controversial documentary film titled A Two-Year-Old Goes to Hospital demonstrating the almost immediate effects of maternal separation. Bowlby's report, coupled with Robertson's film, demonstrated the importance of the primary caregiver in human and non-human primate development.

Partial and total isolation of infant monkeys
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.

In the total isolation experiments baby monkeys would be left alone for three, six, 12, or 24 months of "total social deprivation." The experiments produced monkeys that were severely psychologically disturbed. Harlow wrote:

Harlow tried to reintegrate the monkeys who had been isolated for six months by placing them with monkeys who had been reared normally. The rehabilitation attempts met with limited success. Harlow wrote that total social isolation for the first six months of life produced "severe deficits in virtually every aspect of social behavior." Isolates exposed to monkeys the same age who were reared normally "achieved only limited recovery of simple social responses." Some monkey mothers reared in isolation exhibited "acceptable maternal behavior when forced to accept infant contact over a period of months, but showed no further recovery." Isolates given to surrogate mothers developed "crude interactive patterns among themselves." Opposed to this, when six-month isolates were exposed to younger, three-month-old monkeys, they achieved "essentially complete social recovery for all situations tested." The findings were confirmed by other researchers, who found no difference between peer-therapy recipients and mother-reared infants, but found that artificial surrogates had very little effect.

Pit of despair


Harlow was well known for refusing to use euphemisms and instead chose deliberately outrageous terms for the experimental apparatus he devised, including a forced mating device he called a "rape rack," tormenting surrogate mother devices he called "iron maidens," and in about 1971, an isolation chamber he called the "pit of despair" developed by him and a student, Steven Suomi, now director of the National Institute of Child Health and Human Development's Comparative Ethology Laboratory, at the National Institutes of Health.

In the latter of these devices, alternatively called the "well of despair," baby monkeys were left alone in darkness for up to six weeks or repetitively separated from their peers and isolated in the chamber. These procedures quickly produced monkeys that were severely psychologically disturbed and declared to be valuable models of human depression.

Harlow tried to rehabilitate monkeys that had been subjected to varying degrees of isolation using various forms of therapy. "In our study of psychopathology, we began as sadists trying to produce abnormality. Today we are psychiatrists trying to achieve normality and equanimity." (p.458)