What happens when baby monkeys are given food but denied warmth, comfort, and contact?
This episode examines Harry Harlow’s disturbing experiments and how they changed what we know about love and attachment.
[00:00:05] Hello, hello, hello, and welcome to English Learning for Curious Minds, by Leonardo English, the show where you can listen to fascinating stories and learn weird and wonderful things about the world at the same time as improving your English.
[00:00:22] I'm Alastair Budge, and this is part two of our three-part mini-series on The Dark Side of Psychology, where we'll look at three of the most famous and uncomfortable experiments in the history of the mind.
[00:00:36] In part one, we looked at the Milgram experiment and the idea of obedience to authority.
[00:00:43] In part three, we'll travel to the psychiatric hospitals of 1970s America for the Rosenhan experiment.
[00:00:51] But today, in part two, we turn to the work of an American psychologist named Harry Harlow.
[00:00:58] It's a fascinating story, but I do need to give you a little warning. This episode discusses distressing experiments involving infant monkeys, including isolation and cruelty. So please do take that into account before continuing.
[00:01:16] OK then, let's not waste a minute and get right into it.
[00:01:22] "What is love?"
[00:01:24] It's a question people have been asking since the dawn of time. Aristotle, Plato, and if you grew up in the 1990s like me, the classic Eurodance song by Haddaway.
[00:01:38] It's what, all being well, you feel for the most special people in your life.
[00:01:44] It's what a parent feels for their child.
[00:01:47] It's what a child feels for their parent, some of the time at least.
[00:01:52] But where does it come from? What actually is it?
[00:01:57] Does a new-born child "love" its mother, and if so, why?
[00:02:04] Well, if you were to ask the prominent early 20th century American psychologist John B. Watson, he would tell you that love was an automatic response to being touched, being caressed.
[00:02:21] In much the same way as an infant instinctively fears certain things or gets upset when they are made to do something they do not want to do, love is an automatic reaction to external stimuli. Nothing more.
[00:02:38] And too much touching, too much affection towards a child, well, it could be dangerous. It would make them weak, clingy, dependent on their parent, unable to face the world alone when the time came.
[00:02:56] In 1928, he published his recommendations in a book, Psychological Care of Infant and Child. It was wildly successful, selling more than a hundred thousand copies in its first few months, and becoming the go-to manual on child-rearing.
[00:03:17] It was unambiguous.
[00:03:20] Do not hug your child. Do not kiss them. Do not let them sit on your lap.
[00:03:28] If you must show affection, perhaps a kiss on the forehead when they go to bed, or a handshake in the morning.
[00:03:38] This might sound extraordinary now. But Watson was not a fringe figure. He was the founder of behaviourism, the dominant school in American psychology for the first half of the twentieth century.
[00:03:54] Behaviourism held that human beings could be understood as the sum of their conditioned responses. You learned what you were rewarded for.
[00:04:06] Affection, in this framework, was unnecessary, sentimental, and possibly harmful.
[00:04:14] And this had practical consequences.
[00:04:18] American hospitals often separated newborns from their mothers immediately after birth, keeping them in central nurseries to be brought out only for feeding.
[00:04:31] Orphanages and children's hospitals were quiet, clean, and clinical. Babies were fed and changed but rarely held. Some institutions even discouraged staff from picking up babies who were crying, on the grounds that this would teach them to cry for attention.
[00:04:54] Now, the dominant theory of why babies became attached to their mothers in the first place was just as cold.
[00:05:03] It was called the "cupboard love" theory, and the logic ran like this.
[00:05:10] The baby is hungry. The mother provides food. The baby learns to associate the mother with the satisfaction of hunger. Therefore the baby comes to love the mother.
[00:05:25] Love, in other words, was a side effect of feeding. It was learned, not innate.
[00:05:32] It was about the cupboard, the source of the food, not the person.
[00:05:37] So, don't give your child too much affection, hold and feed them only when necessary, otherwise they will become emotionally dependent on you.
[00:05:49] Now, even by the late 1940s, there was increasing evidence to suggest this theory might not hold water, and that the results from treating infants in this way were mixed.
[00:06:04] A psychoanalyst named René Spitz had documented the mortality rates of infants in orphanages and foundling hospitals across Europe and the Americas.
[00:06:15] The babies were being fed. They were being kept warm. On the surface, their basic physical needs were being met; they were being treated properly.
[00:06:26] And yet they were dying, in some institutions at rates of over thirty per cent in the first year of life. The survivors were often developmentally damaged, withdrawn, and unable to form normal relationships.
[00:06:45] Spitz documented babies who had stopped vocalising. Babies who had stopped reaching for objects. Babies who lay in their cots with empty eyes, no longer responding when staff approached them.
[00:07:00] In the medical language of the time, they were said to have wasted away.
[00:07:06] Spitz called what he saw "hospitalism."
[00:07:11] Something about the absence of physical contact and emotional connection, he thought, was killing these children.
[00:07:19] He couldn't prove it, and the dominant theory of the time — behaviourism — suggested that there was nothing wrong with this. Physical contact was not just unnecessary, but could also be dangerous to the development of a child.
[00:07:37] Yet what Spitz saw in these hospitals and orphanages suggested otherwise.
[00:07:44] What the field needed was an experiment.
[00:07:48] In 1957, in a laboratory at the University of Wisconsin, a fifty-two-year-old psychologist named Harry Harlow began work on what would become the most influential set of experiments in the history of developmental psychology.
[00:08:06] Harlow ran the Primate Laboratory at Wisconsin.
[00:08:11] He had been studying rhesus monkeys for years, mostly investigating their problem-solving and learning.
[00:08:20] He needed a steady supply of monkeys, and would raise them in his laboratory, often in isolation, for the practical purpose of keeping them disease-free.
[00:08:34] And he noticed something strange about the baby monkeys, the ones who were being raised without any contact with their mother, or any other monkey for that matter.
[00:08:45] They clung to the cloth nappies that lined the floors of their cages. If the nappies were taken away to be cleaned, the baby monkeys became distressed. They wrapped themselves around the cloth as if it were a parent. These baby monkeys seemingly just wanted to hold something. They craved contact.
[00:09:10] This made no sense when looked at through the lens of the theories of the time.
[00:09:17] The cloth nappies served no physical purpose — they didn't provide food. So why were the monkeys forming what looked like an emotional attachment to a piece of fabric?
[00:09:31] Harlow designed an experiment to investigate.
[00:09:35] He built two surrogate mothers. Each was roughly the size of a rhesus monkey, with a crude face stuck on the top to look like a head.
[00:09:47] One was made of bare wire mesh. It was hard, cold, and uncomfortable to touch. But it had a bottle of milk, fitted into its chest, from which the baby monkey could feed.
[00:10:04] The other surrogate was wrapped in soft, brown cloth. It was warm. It was comfortable. But it had no milk.
[00:10:15] Both surrogates looked more or less the same. And if the cupboard love theory was correct, the baby monkeys should bond with the milk-providing wire mother. That was where their food came from. That was where, according to behaviourist theory, attachment should form.
[00:10:38] As you might have guessed, that is not what happened.
[00:10:43] The baby monkeys spent almost all their time clinging to the cloth mother. They went to the wire mother only when they were hungry. They fed quickly, and returned. They slept on the cloth mother.
[00:11:00] When something frightening was introduced into the cage, like a loud mechanical toy banging across the floor, they ran to the cloth mother and clung to her for comfort, even though she had never given them anything.
[00:11:16] The baby monkeys were bonding to the source of comfort, not to the source of food.
[00:11:24] Contact, warmth, softness. It seemed that these were as much of a basic need as the need for food.
[00:11:34] In 1958, Harlow gave a now-famous address to the American Psychological Association titled "The Nature of Love."
[00:11:45] He stood in front of his colleagues, many of whom had spent their careers explaining love as a secondary, learned response, and he told them in no uncertain terms that they were wrong.
[00:12:00] Love, he said, was about touch. It was about closeness. It was a primary biological need, not a luxury.
[00:12:11] This was followed up with a series of different and ever-more-controversial experiments.
[00:12:19] In one famous extension, called the "open field" test, Harlow placed baby monkeys in a strange, unfamiliar room full of objects, sometimes with their cloth mother, sometimes with their wire mother, sometimes alone.
[00:12:37] The babies with the cloth mother, after an initial moment of fear, would run to her, cling to her and calm themselves.
[00:12:46] And then, slowly, they would begin to explore.
[00:12:50] They would venture out from the cloth mother to investigate a toy, then run back to her. Then venture further. The cloth mother was a base, a place of safety from which the world could be approached.
[00:13:06] The babies with the wire mother showed none of this. They sat in a corner, paralysed by fear. They did not approach the wire mother for comfort, because she did not provide any.
[00:13:20] They did not explore. The world remained, for them, an unmanageable place.
[00:13:28] This was the discovery that gave attachment its place in modern developmental psychology.
[00:13:34] A loving, comforting parent was not just nice to have.
[00:13:39] The parent was, literally, the foundation from which children built the courage to engage with the world.
[00:13:47] Harlow also showed that monkeys raised entirely without any mother at all, even a fake one, grew up profoundly damaged.
[00:13:57] They could not socialise with other monkeys. They could not mate. The females who did become mothers, through artificial insemination, were often unable to care for their own babies. Some attacked them, while others ignored them as they starved. It seemed like if they had never felt maternal comfort in their infancy they were utterly unable to provide it to their offspring.
[00:14:24] Now, the implication for human beings was hard to ignore.
[00:14:29] If a baby monkey needed soft, warm contact in order to develop normally, what did that say about us, about the babies in those silent, clinical orphanage wards, about the prevailing advice to mothers not to hug or show affection towards their children?
[00:14:50] By the early 1960s, Harlow had become one of the most influential psychologists in America.
[00:14:58] He had been on the cover of news magazines. His monkey experiments were used as examples in every introductory psychology textbook.
[00:15:08] But the work he is now most criticised for was still to come.
[00:15:15] In the 1960s and into the 1970s, Harlow's work on isolation became more extreme, and I'm sorry but here's where it starts to become a little more difficult.
[00:15:28] He wanted to study not just the development of love, but its absence. What happens to a creature deprived of comfort entirely?
[00:15:41] He built what he called a "vertical chamber apparatus." It was a small, stainless steel box, shaped like an upside-down pyramid, with smooth, sloping sides that prevented any kind of grip.
[00:15:57] Baby monkeys were placed inside, alone, for periods ranging from a few days to months at a time.
[00:16:07] In his notes, Harlow called it "the pit of despair."
[00:16:12] The monkeys that came out were broken.
[00:16:16] They sat in corners, rocking back and forth, hugging themselves. They would not eat properly. They would not interact with other monkeys. They were the closest thing anyone had ever produced to a clinical model of severe depression in a non-human animal.
[00:16:35] Harlow's official purpose was research into depression.
[00:16:40] He believed that if he could produce something like depression in an animal, he could study its mechanisms and perhaps find treatments that would help human beings. And his work did produce real findings about the biology of depression and the long-term effects of early deprivation.
[00:17:00] But the cost was extreme, and the design of the experiments was, even by the standards of the time, shocking. Today, experiments like these would be considered ethically indefensible.
[00:17:16] And even back then, many of his own colleagues were uncomfortable. His graduate students sometimes refused to take part.
[00:17:26] Yet he went further still. In another set of experiments, he created what he called "rejecting mothers."
[00:17:36] These were surrogate mothers built to actively harm the baby monkey clinging to them. One model would suddenly blow out cold compressed air, blasting the baby off. Another would shake violently. Another would extend brass spikes from its surface.
[00:17:59] In each case, the baby monkey, after being attacked, would crawl back and cling to the rejecting surrogate even more tightly. There was nowhere else to go.
[00:18:12] At this point, even some people who accepted the scientific importance of his earlier work thought he had crossed a line.
[00:18:22] Now, Harlow was not the only professional working on this idea.
[00:18:27] Across the Atlantic, a British psychiatrist named John Bowlby was developing what would become known as attachment theory. This was the idea that the bond between a baby and its primary caregiver is a fundamental psychological need with lifelong consequences.
[00:18:48] Bowlby's interest in the subject was, in some ways, personal.
[00:18:53] He had grown up in an upper-class English family in which the parents barely interacted with their children.
[00:19:02] He was raised primarily by a beloved nanny named Minnie, who sounded like a sort of Mary Poppins figure.
[00:19:11] When Bowlby was four years old, his parents fired Minnie, on the grounds that the boy was becoming too attached to her. The loss devastated him, and he wrote that it had been an experience as painful as the death of a parent.
[00:19:32] His work, the work that came to define the field of attachment, was in part an attempt to understand what had been done to him as a child.
[00:19:43] Bowlby and Harlow were in frequent correspondence, and Harlow's monkey experiments supported Bowlby's theoretical framework.
[00:19:53] Together, their work transformed the field, and had enormous practical consequences.
[00:20:00] Orphanages across the Western world were quietly closed down, or radically reformed, in favour of foster care and adoption.
[00:20:10] Hospital procedures changed. Mothers were no longer routinely separated from their newborns. Fathers were allowed into delivery rooms. Affection was encouraged.
[00:20:24] Essentially this transformed into the general guidance there is in most countries today, that infants need comfort and affection, that you should respond to your baby when it cries, and that holding and cuddling your child is not just nice for you and them, but necessary.
[00:20:44] It's perhaps easy for us today to say "of course this is true, of course babies need to be cuddled", but this was strictly advised against in the best-selling child-rearing manual of the early 20th century.
[00:21:01] And then, in 1989, came a tragic piece of human evidence that seemed to support the central lesson of Harlow’s work.
[00:21:11] In Romania, during the Ceaușescu dictatorship, huge numbers of children had passed through state orphanages. When he was overthrown and Western observers entered the country, they saw the scale of deprivation in these institutions for the first time.
[00:21:31] Tens of thousands of children had been fed and changed, but rarely held, rarely talked to, rarely played with. Many struggled for years afterwards, even after being adopted into loving families. Food, warmth and a bed had not been enough. Without comfort, attention and affection, many had been deeply scarred.
[00:21:59] Romania had become one of the most tragic natural experiments in early deprivation. It did not mirror Harlow’s laboratory work exactly, of course. But it powerfully supported his central idea: young primates, human or otherwise, need more than food to develop.
[00:22:20] Now, I haven't yet told you anything, really, about Harlow himself.
[00:22:25] He was, by most accounts, not a kind person.
[00:22:30] He had grown up in a household with a depressive father and a distant mother.
[00:22:36] He was sharp-tongued and often cruel to those who worked for him. He was married three times.
[00:22:43] He drank heavily. He suffered serious depression himself, severe enough that he was hospitalised and treated with electroconvulsive therapy.
[00:22:54] He seemed to show no affection towards his monkeys, once saying 'The only thing I care about is whether the monkeys will turn out a property I can publish. I don't have any love for them. Never have. I don't really like animals. I despise cats, I hate dogs. How could you like a monkey?'
[00:23:12] By his own description, he was a man who couldn't really love anything.
[00:23:19] It is, perhaps, odd.
[00:23:21] Here was a man whose greatest contribution to science was demonstrating that love and physical comfort were basic needs of all primates. Yet, by most accounts, he was incapable of giving either.
[00:23:36] Now, to wrap things up, there's one more thing worth saying about this experiment, and about Harlow's legacy.
[00:23:43] And that is that he made love measurable.
[00:23:47] Before Harlow, love had been the province of the poets. A thing of feeling, of metaphor, of sentiment. After Harlow, you could record it in an experimental log.
[00:24:01] You could draw a graph of it. You could measure, with cold scientific precision, the difference between a creature that had received it and one that had not.
[00:24:14] There is, maybe, something almost poetic about that. The cold-hearted, lonely man in his Wisconsin laboratory took the most romantic concept human beings have, and proved it was real.
[00:24:30] OK, then, that is it for today's episode, the second part of our three-part series on The Dark Side of Psychology.
[00:24:38] In our final part, we'll be heading to the psychiatric hospitals of 1970s America for the Rosenhan experiment, in which eight perfectly sane volunteers checked themselves in, and then had a much harder time getting out than they had bargained for.
[00:24:54] You've been listening to English Learning for Curious Minds by Leonardo English.
[00:24:59] I'm Alastair Budge, you stay safe, and I'll catch you in the next episode.
[00:00:05] Hello, hello, hello, and welcome to English Learning for Curious Minds, by Leonardo English, the show where you can listen to fascinating stories and learn weird and wonderful things about the world at the same time as improving your English.
[00:00:22] I'm Alastair Budge, and this is part two of our three-part mini-series on The Dark Side of Psychology, where we'll look at three of the most famous and uncomfortable experiments in the history of the mind.
[00:00:36] In part one, we looked at the Milgram experiment and the idea of obedience to authority.
[00:00:43] In part three, we'll travel to the psychiatric hospitals of 1970s America for the Rosenhan experiment.
[00:00:51] But today, in part two, we turn to the work of an American psychologist named Harry Harlow.
[00:00:58] It's a fascinating story, but I do need to give you a little warning. This episode discusses distressing experiments involving infant monkeys, including isolation and cruelty. So please do take that into account before continuing.
[00:01:16] OK then, let's not waste a minute and get right into it.
[00:01:22] "What is love?"
[00:01:24] It's a question people have been asking since the dawn of time. Aristotle, Plato, and if you grew up in the 1990s like me, the classic Eurodance song by Haddaway.
[00:01:38] It's what, all being well, you feel for the most special people in your life.
[00:01:44] It's what a parent feels for their child.
[00:01:47] It's what a child feels for their parent, some of the time at least.
[00:01:52] But where does it come from? What actually is it?
[00:01:57] Does a new-born child "love" its mother, and if so, why?
[00:02:04] Well, if you were to ask the prominent early 20th century American psychologist John B. Watson, he would tell you that love was an automatic response to being touched, being caressed.
[00:02:21] In much the same way as an infant instinctively fears certain things or gets upset when they are made to do something they do not want to do, love is an automatic reaction to external stimuli. Nothing more.
[00:02:38] And too much touching, too much affection towards a child, well, it could be dangerous. It would make them weak, clingy, dependent on their parent, unable to face the world alone when the time came.
[00:02:56] In 1928, he published his recommendations in a book, Psychological Care of Infant and Child. It was wildly successful, selling more than a hundred thousand copies in its first few months, and becoming the go-to manual on child-rearing.
[00:03:17] It was unambiguous.
[00:03:20] Do not hug your child. Do not kiss them. Do not let them sit on your lap.
[00:03:28] If you must show affection, perhaps a kiss on the forehead when they go to bed, or a handshake in the morning.
[00:03:38] This might sound extraordinary now. But Watson was not a fringe figure. He was the founder of behaviourism, the dominant school in American psychology for the first half of the twentieth century.
[00:03:54] Behaviourism held that human beings could be understood as the sum of their conditioned responses. You learned what you were rewarded for.
[00:04:06] Affection, in this framework, was unnecessary, sentimental, and possibly harmful.
[00:04:14] And this had practical consequences.
[00:04:18] American hospitals often separated newborns from their mothers immediately after birth, keeping them in central nurseries to be brought out only for feeding.
[00:04:31] Orphanages and children's hospitals were quiet, clean, and clinical. Babies were fed and changed but rarely held. Some institutions even discouraged staff from picking up babies who were crying, on the grounds that this would teach them to cry for attention.
[00:04:54] Now, the dominant theory of why babies became attached to their mothers in the first place was just as cold.
[00:05:03] It was called the "cupboard love" theory, and the logic ran like this.
[00:05:10] The baby is hungry. The mother provides food. The baby learns to associate the mother with the satisfaction of hunger. Therefore the baby comes to love the mother.
[00:05:25] Love, in other words, was a side effect of feeding. It was learned, not innate.
[00:05:32] It was about the cupboard, the source of the food, not the person.
[00:05:37] So, don't give your child too much affection, hold and feed them only when necessary, otherwise they will become emotionally dependent on you.
[00:05:49] Now, even by the late 1940s, there was increasing evidence to suggest this theory might not hold water, and that the results from treating infants in this way were mixed.
[00:06:04] A psychoanalyst named René Spitz had documented the mortality rates of infants in orphanages and foundling hospitals across Europe and the Americas.
[00:06:15] The babies were being fed. They were being kept warm. On the surface, their basic physical needs were being met; they were being treated properly.
[00:06:26] And yet they were dying, in some institutions at rates of over thirty per cent in the first year of life. The survivors were often developmentally damaged, withdrawn, and unable to form normal relationships.
[00:06:45] Spitz documented babies who had stopped vocalising. Babies who had stopped reaching for objects. Babies who lay in their cots with empty eyes, no longer responding when staff approached them.
[00:07:00] In the medical language of the time, they were said to have wasted away.
[00:07:06] Spitz called what he saw "hospitalism."
[00:07:11] Something about the absence of physical contact and emotional connection, he thought, was killing these children.
[00:07:19] He couldn't prove it, and the dominant theory of the time — behaviourism — suggested that there was nothing wrong with this. Physical contact was not just unnecessary, but could also be dangerous to the development of a child.
[00:07:37] Yet what Spitz saw in these hospitals and orphanages suggested otherwise.
[00:07:44] What the field needed was an experiment.
[00:07:48] In 1957, in a laboratory at the University of Wisconsin, a fifty-two-year-old psychologist named Harry Harlow began work on what would become the most influential set of experiments in the history of developmental psychology.
[00:08:06] Harlow ran the Primate Laboratory at Wisconsin.
[00:08:11] He had been studying rhesus monkeys for years, mostly investigating their problem-solving and learning.
[00:08:20] He needed a steady supply of monkeys, and would raise them in his laboratory, often in isolation, for the practical purpose of keeping them disease-free.
[00:08:34] And he noticed something strange about the baby monkeys, the ones who were being raised without any contact with their mother, or any other monkey for that matter.
[00:08:45] They clung to the cloth nappies that lined the floors of their cages. If the nappies were taken away to be cleaned, the baby monkeys became distressed. They wrapped themselves around the cloth as if it were a parent. These baby monkeys seemingly just wanted to hold something. They craved contact.
[00:09:10] This made no sense when looked at through the lens of the theories of the time.
[00:09:17] The cloth nappies served no physical purpose — they didn't provide food. So why were the monkeys forming what looked like an emotional attachment to a piece of fabric?
[00:09:31] Harlow designed an experiment to investigate.
[00:09:35] He built two surrogate mothers. Each was roughly the size of a rhesus monkey, with a crude face stuck on the top to look like a head.
[00:09:47] One was made of bare wire mesh. It was hard, cold, and uncomfortable to touch. But it had a bottle of milk, fitted into its chest, from which the baby monkey could feed.
[00:10:04] The other surrogate was wrapped in soft, brown cloth. It was warm. It was comfortable. But it had no milk.
[00:10:15] Both surrogates looked more or less the same. And if the cupboard love theory was correct, the baby monkeys should bond with the milk-providing wire mother. That was where their food came from. That was where, according to behaviourist theory, attachment should form.
[00:10:38] As you might have guessed, that is not what happened.
[00:10:43] The baby monkeys spent almost all their time clinging to the cloth mother. They went to the wire mother only when they were hungry. They fed quickly, and returned. They slept on the cloth mother.
[00:11:00] When something frightening was introduced into the cage, like a loud mechanical toy banging across the floor, they ran to the cloth mother and clung to her for comfort, even though she had never given them anything.
[00:11:16] The baby monkeys were bonding to the source of comfort, not to the source of food.
[00:11:24] Contact, warmth, softness. It seemed that these were as much of a basic need as the need for food.
[00:11:34] In 1958, Harlow gave a now-famous address to the American Psychological Association titled "The Nature of Love."
[00:11:45] He stood in front of his colleagues, many of whom had spent their careers explaining love as a secondary, learned response, and he told them in no uncertain terms that they were wrong.
[00:12:00] Love, he said, was about touch. It was about closeness. It was a primary biological need, not a luxury.
[00:12:11] This was followed up with a series of different and ever-more-controversial experiments.
[00:12:19] In one famous extension, called the "open field" test, Harlow placed baby monkeys in a strange, unfamiliar room full of objects, sometimes with their cloth mother, sometimes with their wire mother, sometimes alone.
[00:12:37] The babies with the cloth mother, after an initial moment of fear, would run to her, cling to her and calm themselves.
[00:12:46] And then, slowly, they would begin to explore.
[00:12:50] They would venture out from the cloth mother to investigate a toy, then run back to her. Then venture further. The cloth mother was a base, a place of safety from which the world could be approached.
[00:13:06] The babies with the wire mother showed none of this. They sat in a corner, paralysed by fear. They did not approach the wire mother for comfort, because she did not provide any.
[00:13:20] They did not explore. The world remained, for them, an unmanageable place.
[00:13:28] This was the discovery that gave attachment its place in modern developmental psychology.
[00:13:34] A loving, comforting parent was not just nice to have.
[00:13:39] The parent was, literally, the foundation from which children built the courage to engage with the world.
[00:13:47] Harlow also showed that monkeys raised entirely without any mother at all, even a fake one, grew up profoundly damaged.
[00:13:57] They could not socialise with other monkeys. They could not mate. The females who did become mothers, through artificial insemination, were often unable to care for their own babies. Some attacked them, while others ignored them as they starved. It seemed like if they had never felt maternal comfort in their infancy they were utterly unable to provide it to their offspring.
[00:14:24] Now, the implication for human beings was hard to ignore.
[00:14:29] If a baby monkey needed soft, warm contact in order to develop normally, what did that say about us, about the babies in those silent, clinical orphanage wards, about the prevailing advice to mothers not to hug or show affection towards their children?
[00:14:50] By the early 1960s, Harlow had become one of the most influential psychologists in America.
[00:14:58] He had been on the cover of news magazines. His monkey experiments were used as examples in every introductory psychology textbook.
[00:15:08] But the work he is now most criticised for was still to come.
[00:15:15] In the 1960s and into the 1970s, Harlow's work on isolation became more extreme, and I'm sorry but here's where it starts to become a little more difficult.
[00:15:28] He wanted to study not just the development of love, but its absence. What happens to a creature deprived of comfort entirely?
[00:15:41] He built what he called a "vertical chamber apparatus." It was a small, stainless steel box, shaped like an upside-down pyramid, with smooth, sloping sides that prevented any kind of grip.
[00:15:57] Baby monkeys were placed inside, alone, for periods ranging from a few days to months at a time.
[00:16:07] In his notes, Harlow called it "the pit of despair."
[00:16:12] The monkeys that came out were broken.
[00:16:16] They sat in corners, rocking back and forth, hugging themselves. They would not eat properly. They would not interact with other monkeys. They were the closest thing anyone had ever produced to a clinical model of severe depression in a non-human animal.
[00:16:35] Harlow's official purpose was research into depression.
[00:16:40] He believed that if he could produce something like depression in an animal, he could study its mechanisms and perhaps find treatments that would help human beings. And his work did produce real findings about the biology of depression and the long-term effects of early deprivation.
[00:17:00] But the cost was extreme, and the design of the experiments was, even by the standards of the time, shocking. Today, experiments like these would be considered ethically indefensible.
[00:17:16] And even back then, many of his own colleagues were uncomfortable. His graduate students sometimes refused to take part.
[00:17:26] Yet he went further still. In another set of experiments, he created what he called "rejecting mothers."
[00:17:36] These were surrogate mothers built to actively harm the baby monkey clinging to them. One model would suddenly blow out cold compressed air, blasting the baby off. Another would shake violently. Another would extend brass spikes from its surface.
[00:17:59] In each case, the baby monkey, after being attacked, would crawl back and cling to the rejecting surrogate even more tightly. There was nowhere else to go.
[00:18:12] At this point, even some people who accepted the scientific importance of his earlier work thought he had crossed a line.
[00:18:22] Now, Harlow was not the only professional working on this idea.
[00:18:27] Across the Atlantic, a British psychiatrist named John Bowlby was developing what would become known as attachment theory. This was the idea that the bond between a baby and its primary caregiver is a fundamental psychological need with lifelong consequences.
[00:18:48] Bowlby's interest in the subject was, in some ways, personal.
[00:18:53] He had grown up in an upper-class English family in which the parents barely interacted with their children.
[00:19:02] He was raised primarily by a beloved nanny named Minnie, who sounded like a sort of Mary Poppins figure.
[00:19:11] When Bowlby was four years old, his parents fired Minnie, on the grounds that the boy was becoming too attached to her. The loss devastated him, and he wrote that it had been an experience as painful as the death of a parent.
[00:19:32] His work, the work that came to define the field of attachment, was in part an attempt to understand what had been done to him as a child.
[00:19:43] Bowlby and Harlow were in frequent correspondence, and Harlow's monkey experiments supported Bowlby's theoretical framework.
[00:19:53] Together, their work transformed the field, and had enormous practical consequences.
[00:20:00] Orphanages across the Western world were quietly closed down, or radically reformed, in favour of foster care and adoption.
[00:20:10] Hospital procedures changed. Mothers were no longer routinely separated from their newborns. Fathers were allowed into delivery rooms. Affection was encouraged.
[00:20:24] Essentially this transformed into the general guidance there is in most countries today, that infants need comfort and affection, that you should respond to your baby when it cries, and that holding and cuddling your child is not just nice for you and them, but necessary.
[00:20:44] It's perhaps easy for us today to say "of course this is true, of course babies need to be cuddled", but this was strictly advised against in the best-selling child-rearing manual of the early 20th century.
[00:21:01] And then, in 1989, came a tragic piece of human evidence that seemed to support the central lesson of Harlow’s work.
[00:21:11] In Romania, during the Ceaușescu dictatorship, huge numbers of children had passed through state orphanages. When he was overthrown and Western observers entered the country, they saw the scale of deprivation in these institutions for the first time.
[00:21:31] Tens of thousands of children had been fed and changed, but rarely held, rarely talked to, rarely played with. Many struggled for years afterwards, even after being adopted into loving families. Food, warmth and a bed had not been enough. Without comfort, attention and affection, many had been deeply scarred.
[00:21:59] Romania had become one of the most tragic natural experiments in early deprivation. It did not mirror Harlow’s laboratory work exactly, of course. But it powerfully supported his central idea: young primates, human or otherwise, need more than food to develop.
[00:22:20] Now, I haven't yet told you anything, really, about Harlow himself.
[00:22:25] He was, by most accounts, not a kind person.
[00:22:30] He had grown up in a household with a depressive father and a distant mother.
[00:22:36] He was sharp-tongued and often cruel to those who worked for him. He was married three times.
[00:22:43] He drank heavily. He suffered serious depression himself, severe enough that he was hospitalised and treated with electroconvulsive therapy.
[00:22:54] He seemed to show no affection towards his monkeys, once saying 'The only thing I care about is whether the monkeys will turn out a property I can publish. I don't have any love for them. Never have. I don't really like animals. I despise cats, I hate dogs. How could you like a monkey?'
[00:23:12] By his own description, he was a man who couldn't really love anything.
[00:23:19] It is, perhaps, odd.
[00:23:21] Here was a man whose greatest contribution to science was demonstrating that love and physical comfort were basic needs of all primates. Yet, by most accounts, he was incapable of giving either.
[00:23:36] Now, to wrap things up, there's one more thing worth saying about this experiment, and about Harlow's legacy.
[00:23:43] And that is that he made love measurable.
[00:23:47] Before Harlow, love had been the province of the poets. A thing of feeling, of metaphor, of sentiment. After Harlow, you could record it in an experimental log.
[00:24:01] You could draw a graph of it. You could measure, with cold scientific precision, the difference between a creature that had received it and one that had not.
[00:24:14] There is, maybe, something almost poetic about that. The cold-hearted, lonely man in his Wisconsin laboratory took the most romantic concept human beings have, and proved it was real.
[00:24:30] OK, then, that is it for today's episode, the second part of our three-part series on The Dark Side of Psychology.
[00:24:38] In our final part, we'll be heading to the psychiatric hospitals of 1970s America for the Rosenhan experiment, in which eight perfectly sane volunteers checked themselves in, and then had a much harder time getting out than they had bargained for.
[00:24:54] You've been listening to English Learning for Curious Minds by Leonardo English.
[00:24:59] I'm Alastair Budge, you stay safe, and I'll catch you in the next episode.
[00:00:05] Hello, hello, hello, and welcome to English Learning for Curious Minds, by Leonardo English, the show where you can listen to fascinating stories and learn weird and wonderful things about the world at the same time as improving your English.
[00:00:22] I'm Alastair Budge, and this is part two of our three-part mini-series on The Dark Side of Psychology, where we'll look at three of the most famous and uncomfortable experiments in the history of the mind.
[00:00:36] In part one, we looked at the Milgram experiment and the idea of obedience to authority.
[00:00:43] In part three, we'll travel to the psychiatric hospitals of 1970s America for the Rosenhan experiment.
[00:00:51] But today, in part two, we turn to the work of an American psychologist named Harry Harlow.
[00:00:58] It's a fascinating story, but I do need to give you a little warning. This episode discusses distressing experiments involving infant monkeys, including isolation and cruelty. So please do take that into account before continuing.
[00:01:16] OK then, let's not waste a minute and get right into it.
[00:01:22] "What is love?"
[00:01:24] It's a question people have been asking since the dawn of time. Aristotle, Plato, and if you grew up in the 1990s like me, the classic Eurodance song by Haddaway.
[00:01:38] It's what, all being well, you feel for the most special people in your life.
[00:01:44] It's what a parent feels for their child.
[00:01:47] It's what a child feels for their parent, some of the time at least.
[00:01:52] But where does it come from? What actually is it?
[00:01:57] Does a new-born child "love" its mother, and if so, why?
[00:02:04] Well, if you were to ask the prominent early 20th century American psychologist John B. Watson, he would tell you that love was an automatic response to being touched, being caressed.
[00:02:21] In much the same way as an infant instinctively fears certain things or gets upset when they are made to do something they do not want to do, love is an automatic reaction to external stimuli. Nothing more.
[00:02:38] And too much touching, too much affection towards a child, well, it could be dangerous. It would make them weak, clingy, dependent on their parent, unable to face the world alone when the time came.
[00:02:56] In 1928, he published his recommendations in a book, Psychological Care of Infant and Child. It was wildly successful, selling more than a hundred thousand copies in its first few months, and becoming the go-to manual on child-rearing.
[00:03:17] It was unambiguous.
[00:03:20] Do not hug your child. Do not kiss them. Do not let them sit on your lap.
[00:03:28] If you must show affection, perhaps a kiss on the forehead when they go to bed, or a handshake in the morning.
[00:03:38] This might sound extraordinary now. But Watson was not a fringe figure. He was the founder of behaviourism, the dominant school in American psychology for the first half of the twentieth century.
[00:03:54] Behaviourism held that human beings could be understood as the sum of their conditioned responses. You learned what you were rewarded for.
[00:04:06] Affection, in this framework, was unnecessary, sentimental, and possibly harmful.
[00:04:14] And this had practical consequences.
[00:04:18] American hospitals often separated newborns from their mothers immediately after birth, keeping them in central nurseries to be brought out only for feeding.
[00:04:31] Orphanages and children's hospitals were quiet, clean, and clinical. Babies were fed and changed but rarely held. Some institutions even discouraged staff from picking up babies who were crying, on the grounds that this would teach them to cry for attention.
[00:04:54] Now, the dominant theory of why babies became attached to their mothers in the first place was just as cold.
[00:05:03] It was called the "cupboard love" theory, and the logic ran like this.
[00:05:10] The baby is hungry. The mother provides food. The baby learns to associate the mother with the satisfaction of hunger. Therefore the baby comes to love the mother.
[00:05:25] Love, in other words, was a side effect of feeding. It was learned, not innate.
[00:05:32] It was about the cupboard, the source of the food, not the person.
[00:05:37] So, don't give your child too much affection, hold and feed them only when necessary, otherwise they will become emotionally dependent on you.
[00:05:49] Now, even by the late 1940s, there was increasing evidence to suggest this theory might not hold water, and that the results from treating infants in this way were mixed.
[00:06:04] A psychoanalyst named René Spitz had documented the mortality rates of infants in orphanages and foundling hospitals across Europe and the Americas.
[00:06:15] The babies were being fed. They were being kept warm. On the surface, their basic physical needs were being met; they were being treated properly.
[00:06:26] And yet they were dying, in some institutions at rates of over thirty per cent in the first year of life. The survivors were often developmentally damaged, withdrawn, and unable to form normal relationships.
[00:06:45] Spitz documented babies who had stopped vocalising. Babies who had stopped reaching for objects. Babies who lay in their cots with empty eyes, no longer responding when staff approached them.
[00:07:00] In the medical language of the time, they were said to have wasted away.
[00:07:06] Spitz called what he saw "hospitalism."
[00:07:11] Something about the absence of physical contact and emotional connection, he thought, was killing these children.
[00:07:19] He couldn't prove it, and the dominant theory of the time — behaviourism — suggested that there was nothing wrong with this. Physical contact was not just unnecessary, but could also be dangerous to the development of a child.
[00:07:37] Yet what Spitz saw in these hospitals and orphanages suggested otherwise.
[00:07:44] What the field needed was an experiment.
[00:07:48] In 1957, in a laboratory at the University of Wisconsin, a fifty-two-year-old psychologist named Harry Harlow began work on what would become the most influential set of experiments in the history of developmental psychology.
[00:08:06] Harlow ran the Primate Laboratory at Wisconsin.
[00:08:11] He had been studying rhesus monkeys for years, mostly investigating their problem-solving and learning.
[00:08:20] He needed a steady supply of monkeys, and would raise them in his laboratory, often in isolation, for the practical purpose of keeping them disease-free.
[00:08:34] And he noticed something strange about the baby monkeys, the ones who were being raised without any contact with their mother, or any other monkey for that matter.
[00:08:45] They clung to the cloth nappies that lined the floors of their cages. If the nappies were taken away to be cleaned, the baby monkeys became distressed. They wrapped themselves around the cloth as if it were a parent. These baby monkeys seemingly just wanted to hold something. They craved contact.
[00:09:10] This made no sense when looked at through the lens of the theories of the time.
[00:09:17] The cloth nappies served no physical purpose — they didn't provide food. So why were the monkeys forming what looked like an emotional attachment to a piece of fabric?
[00:09:31] Harlow designed an experiment to investigate.
[00:09:35] He built two surrogate mothers. Each was roughly the size of a rhesus monkey, with a crude face stuck on the top to look like a head.
[00:09:47] One was made of bare wire mesh. It was hard, cold, and uncomfortable to touch. But it had a bottle of milk, fitted into its chest, from which the baby monkey could feed.
[00:10:04] The other surrogate was wrapped in soft, brown cloth. It was warm. It was comfortable. But it had no milk.
[00:10:15] Both surrogates looked more or less the same. And if the cupboard love theory was correct, the baby monkeys should bond with the milk-providing wire mother. That was where their food came from. That was where, according to behaviourist theory, attachment should form.
[00:10:38] As you might have guessed, that is not what happened.
[00:10:43] The baby monkeys spent almost all their time clinging to the cloth mother. They went to the wire mother only when they were hungry. They fed quickly, and returned. They slept on the cloth mother.
[00:11:00] When something frightening was introduced into the cage, like a loud mechanical toy banging across the floor, they ran to the cloth mother and clung to her for comfort, even though she had never given them anything.
[00:11:16] The baby monkeys were bonding to the source of comfort, not to the source of food.
[00:11:24] Contact, warmth, softness. It seemed that these were as much of a basic need as the need for food.
[00:11:34] In 1958, Harlow gave a now-famous address to the American Psychological Association titled "The Nature of Love."
[00:11:45] He stood in front of his colleagues, many of whom had spent their careers explaining love as a secondary, learned response, and he told them in no uncertain terms that they were wrong.
[00:12:00] Love, he said, was about touch. It was about closeness. It was a primary biological need, not a luxury.
[00:12:11] This was followed up with a series of different and ever-more-controversial experiments.
[00:12:19] In one famous extension, called the "open field" test, Harlow placed baby monkeys in a strange, unfamiliar room full of objects, sometimes with their cloth mother, sometimes with their wire mother, sometimes alone.
[00:12:37] The babies with the cloth mother, after an initial moment of fear, would run to her, cling to her and calm themselves.
[00:12:46] And then, slowly, they would begin to explore.
[00:12:50] They would venture out from the cloth mother to investigate a toy, then run back to her. Then venture further. The cloth mother was a base, a place of safety from which the world could be approached.
[00:13:06] The babies with the wire mother showed none of this. They sat in a corner, paralysed by fear. They did not approach the wire mother for comfort, because she did not provide any.
[00:13:20] They did not explore. The world remained, for them, an unmanageable place.
[00:13:28] This was the discovery that gave attachment its place in modern developmental psychology.
[00:13:34] A loving, comforting parent was not just nice to have.
[00:13:39] The parent was, literally, the foundation from which children built the courage to engage with the world.
[00:13:47] Harlow also showed that monkeys raised entirely without any mother at all, even a fake one, grew up profoundly damaged.
[00:13:57] They could not socialise with other monkeys. They could not mate. The females who did become mothers, through artificial insemination, were often unable to care for their own babies. Some attacked them, while others ignored them as they starved. It seemed like if they had never felt maternal comfort in their infancy they were utterly unable to provide it to their offspring.
[00:14:24] Now, the implication for human beings was hard to ignore.
[00:14:29] If a baby monkey needed soft, warm contact in order to develop normally, what did that say about us, about the babies in those silent, clinical orphanage wards, about the prevailing advice to mothers not to hug or show affection towards their children?
[00:14:50] By the early 1960s, Harlow had become one of the most influential psychologists in America.
[00:14:58] He had been on the cover of news magazines. His monkey experiments were used as examples in every introductory psychology textbook.
[00:15:08] But the work he is now most criticised for was still to come.
[00:15:15] In the 1960s and into the 1970s, Harlow's work on isolation became more extreme, and I'm sorry but here's where it starts to become a little more difficult.
[00:15:28] He wanted to study not just the development of love, but its absence. What happens to a creature deprived of comfort entirely?
[00:15:41] He built what he called a "vertical chamber apparatus." It was a small, stainless steel box, shaped like an upside-down pyramid, with smooth, sloping sides that prevented any kind of grip.
[00:15:57] Baby monkeys were placed inside, alone, for periods ranging from a few days to months at a time.
[00:16:07] In his notes, Harlow called it "the pit of despair."
[00:16:12] The monkeys that came out were broken.
[00:16:16] They sat in corners, rocking back and forth, hugging themselves. They would not eat properly. They would not interact with other monkeys. They were the closest thing anyone had ever produced to a clinical model of severe depression in a non-human animal.
[00:16:35] Harlow's official purpose was research into depression.
[00:16:40] He believed that if he could produce something like depression in an animal, he could study its mechanisms and perhaps find treatments that would help human beings. And his work did produce real findings about the biology of depression and the long-term effects of early deprivation.
[00:17:00] But the cost was extreme, and the design of the experiments was, even by the standards of the time, shocking. Today, experiments like these would be considered ethically indefensible.
[00:17:16] And even back then, many of his own colleagues were uncomfortable. His graduate students sometimes refused to take part.
[00:17:26] Yet he went further still. In another set of experiments, he created what he called "rejecting mothers."
[00:17:36] These were surrogate mothers built to actively harm the baby monkey clinging to them. One model would suddenly blow out cold compressed air, blasting the baby off. Another would shake violently. Another would extend brass spikes from its surface.
[00:17:59] In each case, the baby monkey, after being attacked, would crawl back and cling to the rejecting surrogate even more tightly. There was nowhere else to go.
[00:18:12] At this point, even some people who accepted the scientific importance of his earlier work thought he had crossed a line.
[00:18:22] Now, Harlow was not the only professional working on this idea.
[00:18:27] Across the Atlantic, a British psychiatrist named John Bowlby was developing what would become known as attachment theory. This was the idea that the bond between a baby and its primary caregiver is a fundamental psychological need with lifelong consequences.
[00:18:48] Bowlby's interest in the subject was, in some ways, personal.
[00:18:53] He had grown up in an upper-class English family in which the parents barely interacted with their children.
[00:19:02] He was raised primarily by a beloved nanny named Minnie, who sounded like a sort of Mary Poppins figure.
[00:19:11] When Bowlby was four years old, his parents fired Minnie, on the grounds that the boy was becoming too attached to her. The loss devastated him, and he wrote that it had been an experience as painful as the death of a parent.
[00:19:32] His work, the work that came to define the field of attachment, was in part an attempt to understand what had been done to him as a child.
[00:19:43] Bowlby and Harlow were in frequent correspondence, and Harlow's monkey experiments supported Bowlby's theoretical framework.
[00:19:53] Together, their work transformed the field, and had enormous practical consequences.
[00:20:00] Orphanages across the Western world were quietly closed down, or radically reformed, in favour of foster care and adoption.
[00:20:10] Hospital procedures changed. Mothers were no longer routinely separated from their newborns. Fathers were allowed into delivery rooms. Affection was encouraged.
[00:20:24] Essentially this transformed into the general guidance there is in most countries today, that infants need comfort and affection, that you should respond to your baby when it cries, and that holding and cuddling your child is not just nice for you and them, but necessary.
[00:20:44] It's perhaps easy for us today to say "of course this is true, of course babies need to be cuddled", but this was strictly advised against in the best-selling child-rearing manual of the early 20th century.
[00:21:01] And then, in 1989, came a tragic piece of human evidence that seemed to support the central lesson of Harlow’s work.
[00:21:11] In Romania, during the Ceaușescu dictatorship, huge numbers of children had passed through state orphanages. When he was overthrown and Western observers entered the country, they saw the scale of deprivation in these institutions for the first time.
[00:21:31] Tens of thousands of children had been fed and changed, but rarely held, rarely talked to, rarely played with. Many struggled for years afterwards, even after being adopted into loving families. Food, warmth and a bed had not been enough. Without comfort, attention and affection, many had been deeply scarred.
[00:21:59] Romania had become one of the most tragic natural experiments in early deprivation. It did not mirror Harlow’s laboratory work exactly, of course. But it powerfully supported his central idea: young primates, human or otherwise, need more than food to develop.
[00:22:20] Now, I haven't yet told you anything, really, about Harlow himself.
[00:22:25] He was, by most accounts, not a kind person.
[00:22:30] He had grown up in a household with a depressive father and a distant mother.
[00:22:36] He was sharp-tongued and often cruel to those who worked for him. He was married three times.
[00:22:43] He drank heavily. He suffered serious depression himself, severe enough that he was hospitalised and treated with electroconvulsive therapy.
[00:22:54] He seemed to show no affection towards his monkeys, once saying 'The only thing I care about is whether the monkeys will turn out a property I can publish. I don't have any love for them. Never have. I don't really like animals. I despise cats, I hate dogs. How could you like a monkey?'
[00:23:12] By his own description, he was a man who couldn't really love anything.
[00:23:19] It is, perhaps, odd.
[00:23:21] Here was a man whose greatest contribution to science was demonstrating that love and physical comfort were basic needs of all primates. Yet, by most accounts, he was incapable of giving either.
[00:23:36] Now, to wrap things up, there's one more thing worth saying about this experiment, and about Harlow's legacy.
[00:23:43] And that is that he made love measurable.
[00:23:47] Before Harlow, love had been the province of the poets. A thing of feeling, of metaphor, of sentiment. After Harlow, you could record it in an experimental log.
[00:24:01] You could draw a graph of it. You could measure, with cold scientific precision, the difference between a creature that had received it and one that had not.
[00:24:14] There is, maybe, something almost poetic about that. The cold-hearted, lonely man in his Wisconsin laboratory took the most romantic concept human beings have, and proved it was real.
[00:24:30] OK, then, that is it for today's episode, the second part of our three-part series on The Dark Side of Psychology.
[00:24:38] In our final part, we'll be heading to the psychiatric hospitals of 1970s America for the Rosenhan experiment, in which eight perfectly sane volunteers checked themselves in, and then had a much harder time getting out than they had bargained for.
[00:24:54] You've been listening to English Learning for Curious Minds by Leonardo English.
[00:24:59] I'm Alastair Budge, you stay safe, and I'll catch you in the next episode.
