How Harry Harlow Used Monkeys For Strange Love Experiments

In the middle of the 20th century, Harry Harlow conducted cruel experiments on baby rhesus monkeys to prove that the bond between mother and child goes beyond the need for food.

The University of Wisconsin-Madison Harry Harlow with one of the rhesus monkeys and his surrogate “mother”.

Harry Harlow was fascinated by the idea of ​​love. Specifically, she wants to explore how infants develop loving bonds with their families. And he did so in several controversial experiments involving baby rhesus monkeys and surrogate “mothers” made of cloth or wire.

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At the time, most scientists believed that babies were motivated to bond with their mothers because of the need for food. Some psychologists even advise parents not to comfort or restrain their children too much, because they may become dependent adults.

But Harlow’s experiments revealed the opposite – when given the choice between a ‘wire’ mother with milk and a ‘cloth’ mother without food, the baby monkeys chose to hang on to the cloth mother. In addition, Harlow showed that children who live alone do not develop social skills.

Harlow’s experiments were controversial and cruel, but they showed an important truth about babies’ need for touch, love, and reassurance.

Born on October 31, 1905, as Harry Israel, Harlow grew up in Fairfield, Iowa, with his parents and three siblings. According to his biographer, Deborah Blum, who writes Love in Goon Park: Harry Harlow and the Science of AffectionHarlow was a kind, if bored, child whose lonely early years were mostly defined by an illness from which his brother, Delmer, suffered.

“I have no recollection of partial maternal separation, but perhaps some percentage of maternal affection was lost,” Harlow later wrote of Delmer’s illness, according to Blum. “[T]its absence may have resulted in satisfying the loneliness of teenagers and adults.

An able student when he got it, Harlow finished 13th in his class of 71 and outperformed all his classmates on an aptitude test administered by the University of Iowa. Yet he had little ambition beyond being “famous”, according to his yearbook – and secretly he feared “going crazy”.

However, Harry Harlow graduated from Stanford University in California in 1924. After struggling as an English major, he switched to psychology and spent six years as an undergraduate. the Stanford-Binet IQ Test.

In fact, it was Terman who suggested that Harlow change his name from “Israel” to avoid the suggestion that he was Jewish. “Terman chose Harlow for me,” Harlow later wrote, “and as far as I know I am the only scientist nominated by his principal.”

After graduating in 1930, Harry Harlow found a professorship at the University of Wisconsin in Madison. And there he would expand his famous – and controversial – experiment on baby rhesus monkeys.

The wire is against. Mother Cotton Experiments

Rhesus monkeys with mothers

Harry Harlow/Public DomainA baby rhesus monkey curls up at the feet of its “cloth” mother, ignoring its “wire” mother.

For more than 20 years, Harry Harlow has worked at the University of Wisconsin in relative obscurity. But in 1957, he began an experiment with baby rhesus monkeys that would make him famous – and infamous.

ACCORDING The New York Times, most scientists at the time agreed that children’s relationships with their mothers were based on food. Therefore, many prominent psychologists advise parents not to hug their children or respond to their cries, because of this they will become too dependent.

“When you are tempted to take care of your child, remember that a mother’s love is a dangerous instrument,” said behaviorist John B. Watson.

But Harry Harlow and others, according to the Association for Psychological Sciences, question that logic. To dig deeper, Harlow began a series of experiments with baby rhesus monkeys in his lab in Wisconsin.

First, Harlow conducted an experiment where he raised baby monkeys in complete isolation. According to the Association for Psychological Science, isolated monkeys wound themselves, walked around their cages and stared. When introduced to others, they didn’t know how to get along – and some stopped eating and died.

Rhesus monkey in the forest

Creative Touch Imaging Ltd./NurPhoto via Getty ImagesA rhesus monkey in the wild holding her baby, the contact Harlow makes is significant.

Significantly, they were also nervous about holding their cloth diapers, which led Harlow to develop the next phase of his study. In this experiment, Harlow took baby monkeys and placed them with two substitute “mothers,” one of wire and the other of soft cloth.

Sometimes the wire mother has a bottle and sometimes the fabric mother has one. But regardless, Harlow found that the baby monkeys spent more time in the mother’s cloth. When the wire mother has milk, the babies approach her to feed, then return to the cloth mother. According to PBS, when the cloth mother had milk, the children ignored the wire mother.

In addition, the mere presence of a surrogate gives children more confidence. When placed in a new environment with a replacement, the monkey explores. If left unattended, the monkey will tremble with fear, scream and cry.

Harlow also tested how having a peer group affects baby monkeys. He found that monkeys who grew up with peers and a mother easily socialized with others. Monkeys with cloth mothers do the same – but it takes longer. However, monkeys with a mother but no peers are fearful and aggressive, and monkeys without one lack social skills.

So what exactly did Harry Harlow’s experiments establish?

Harry Harlow’s legacy today

In his experiments with rhesus monkey babies, Harry Harlow disproved the scientists of his time who believed that physical contact did not matter and that babies were connected to their mothers out of a desire to survive. Instead, he established the concept of “contact comfort.”

Given sufficient contact comfort, Harlow’s experiments suggested, human infants grow up to be well-adjusted members of society. Without it, they become fearful, aggressive, and socially awkward.

Ironically, Harlow has always struggled to form strong relationships in her own life. He had two failed marriages (although he remarried his first wife after his second wife died) and, according to Very Good, could be “sarcastic, mean-spirited, misanthropic, chauvinistic and cruel”.

Furthermore, his experiments are now considered by some to be highly controversial and unethical. By removing infant rhesus monkeys from their mothers, often placing them in solitary confinement, Harlow inflicted severe psychological pain on his subjects. But Harry Harlow may have found his work essential to better understanding one of life’s most powerful emotions.

“Love is a wonderful, deep, tender and rewarding state,” he said when he presented his work at the 66th annual congress of
American Psychological Association in August 1958. Saying that love is “a motive that permeates our whole life”, Harlow added:

“Because of its intimate and personal nature, it is considered by some to be an unsuitable subject for experimental research. However, whatever our personal feelings, our designated mission as psychologists is to analyze all aspects of human and animal behavior in their variable components.

His experiments on rhesus monkeys were controversial. But they also convincingly show how love – or the lack of it – can shape our lives.


After reading about Harry Harlow and his experiences with rhesus monkeys, learn about the twins Jim who were separated at birth but lived very similar lives. Or, go inside the study that suggests monkeys are better at problem solving than humans.

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