thumb|upright|Monkey clinging to the cloth mother surrogate in fear test
Harry Frederick Harlow (October 31, 1905 – December 6, 1981) was an American psychologist best known for his maternal-separation, dependency needs, and social isolation experiments on rhesus monkeys, which manifested the importance of caregiving and companionship to social and cognitive development. He conducted most of his research at the University of Wisconsin–Madison, where humanistic psychologist Abraham Maslow worked with him for a short period of time.
Harlow's experiments were ethically controversial; they included creating inanimate wire and wood surrogate "mothers" for the rhesus infants. Each infant became attached to its particular mother, recognizing its unique face. Harlow then investigated whether the infants had a preference for bare-wire mothers or cloth-covered mothers in different situations: with the wire mother holding a bottle with food, and the cloth mother holding nothing, or with the wire mother holding nothing, while the cloth mother held a bottle with food. The monkeys overwhelmingly chose the cloth mother, with or without food, only visiting the wire mother that had food when needing sustenance.
Later in his career, he cultivated infant monkeys in isolation chambers for up to 12 months, from which they emerged intensely disturbed. Some researchers cite the experiments as a factor in the rise of the animal liberation movement in the United States. A Review of General Psychology survey, published in 2002, ranked Harlow as the 26th most cited psychologist of the 20th century.
Biography
Harry Harlow was born on October 31, 1905, to Mabel Rock and Alonzo Harlow Israel. Harlow was born and raised in Fairfield, Iowa, the third of four brothers. Little is known of Harlow's early life, but in an unfinished autobiography he recollected that his mother was cold to him and he experienced bouts of depression throughout his life. After a year at Reed College in Portland, Oregon, Harlow obtained admission to Stanford University through a special aptitude test. After a semester as an English major with nearly disastrous grades, he declared himself as a psychology major.
Harlow attended Stanford in 1924, and subsequently became a graduate student in psychology, working directly under Calvin Perry Stone, a well-known animal behaviorist, and Walter Richard Miles, a vision expert, who were all supervised by Lewis Terman. The change was made at Terman's prompting for fear of the negative consequences of having a seemingly Jewish last name, even though his family was not Jewish.
Harlow received numerous awards and honors, including election to the United States National Academy of Sciences (1951), the Howard Crosby Warren Medal (1956), election to the American Philosophical Society (1957), the National Medal of Science (1967), election to the American Academy of Arts and Sciences (1961), and the Gold Medal from the American Psychological Foundation (1973). He served as head of the Human Resources Research branch of the Department of the Army from 1950 to 1952, head of the Division of Anthropology and Psychology of the National Research Council from 1952 to 1955, consultant to the Army Scientific Advisory Panel, and president of the American Psychological Association from 1958 to 1959.
thumb|right|200px|Graves of Harlow and Margaret Kuenne at Forest Hill Cemetery
Harlow married his first wife, Clara Mears, in 1932. One of the select students with an IQ above 150 whom Terman studied at Stanford, Clara was Harlow's student before becoming romantically involved with him. The couple had two children together, Robert and Richard. Harlow and Mears divorced in 1946. That same year, Harlow married child psychologist Margaret Kuenne. They had two children together, Pamela and Jonathan. Margaret died on August 11, 1971, after a prolonged struggle with cancer, with which she had been diagnosed in 1967. Her death led Harlow to depression once more, for which he was treated with electro-convulsive therapy. In March 1972, Harlow remarried Clara Mears. The couple lived together in Tucson, Arizona, until Harlow's death in 1981. after obtaining his doctorate under the guidance of several distinguished researchers, including Calvin Stone and Lewis Terman, at Stanford University. He began his career with nonhuman primate research. He worked with the primates at Henry Vilas Zoo, where he developed the Wisconsin General Test Apparatus (WGTA) to study learning, cognition, and memory. It was through these studies that Harlow discovered that the monkeys he worked with were developing strategies for his tests. What would later become known as metalearning, Harlow described as "learning to learn" or "learning sets". At the time, the two competing theories of learning were Hull-Spence, which stated that learning was via trial and error, and Gestalt, which stated learning was via moments of sudden insight. The learning sets showed that there was no real conflict between the two, as learning begins by trial and error, but if a new problem resembles more and more previous problems, then it is more and more likely to be solved suddenly and insightfully.
thumb|upright|Harlow exclusively used rhesus macaques in his experiments.
In order to study the development of these learning sets, Harlow needed access to developing primates, so he established a breeding colony of rhesus macaques in 1932. Due to the nature of his study, Harlow needed regular access to infant primates and thus chose to rear them in a nursery setting, rather than with their protective mothers.
Noticing their attachment to the soft cloth of their diapers and the psychological changes that correlated with the absence of a maternal figure, Harlow sought to investigate the mother–infant bond. such as René Spitz's and 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. Bowlby de-emphasized the mother's role in feeding as a basis for the development of a strong mother–child relationship, but his conclusions generated much debate. It was the debate concerning the reasons behind the demonstrated need for maternal care that Harlow addressed in his studies with surrogates. Physical contact with infants was considered harmful to their development, and this view led to sterile, contact-less nurseries across the country. Bowlby disagreed, claiming that the mother provides much more than food to the infant, including a unique bond that positively influences the child's development and mental health.
To investigate the debate, Harlow created inanimate surrogate mothers for the rhesus infants from wire and wood. In an experiment called the "open-field test", an infant was placed in a novel environment with novel objects. When the infant's surrogate mother was present, it clung to her, but then began venturing off to explore. If frightened, the infant ran back to the surrogate mother and clung to her for a time before venturing out again. Without the surrogate mother's presence, the monkeys were paralyzed with fear, huddling in a ball and sucking their thumbs.
Some of Harlow's final experiments explored social deprivation in the quest to create an animal model for the study of depression. This study is the most controversial, and involved isolation of infant and juvenile macaques for various periods of time. Monkeys placed in isolation exhibited social deficits when introduced or re-introduced into a peer group. They appeared unsure of how to interact with their conspecifics, and mostly stayed separate from the group, demonstrating the importance of social interaction and stimuli in forming the ability to interact with conspecifics in developing monkeys, and, comparatively, in children.
Critics of Harlow's research 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, overestimate the importance of contact comfort and underestimate 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 in Washington, D.C., August 31, 1958.
Partial and total isolation of infant monkeys
Beginning in 1959, 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.
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: