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Harry Harlow Theory & Rhesus Monkey Experiments in Psychology

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Harlow (1958 wanted to study the mechanisms by which newborn rhesus monkeys bond with their mothers.

These infants depended highly on their mothers for nutrition, protection, comfort, and socialization.  What, exactly, though, was the basis of the bond?

The learning theory of attachment suggests that an infant would form an attachment with a carer who provides food. In contrast, Harlow explained that attachment develops due to the mother providing “tactile comfort,” suggesting that infants have an innate (biological) need to touch and cling to something for emotional comfort.

Harry Harlow did a number of studies on attachment in rhesus monkeys during the 1950’s and 1960″s.  His experiments took several forms:

Cloth Mother vs. Wire Mother Experiment

Experiment 1.

Harlow (1958) separated infant monkeys from their mothers immediately after birth and placed in cages with access to two surrogate mothers, one made of wire and one covered in soft terry toweling cloth.

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.

Both groups of monkeys spent more time with the cloth mother (even if she had no milk).  The infant would only go to the wire mother when hungry. Once fed it would return to the cloth mother for most of the day.  If a frightening object was placed in the cage the infant took refuge with the cloth mother (its safe base).

This surrogate was more effective in decreasing the youngster’s fear.  The infant would explore more when the cloth mother was present.

This supports the evolutionary theory of attachment , in that the sensitive response and security of the caregiver are important (as opposed to the provision of food).

Experiment 2

Harlow (1958) modified his experiment and separated the infants into two groups: the terrycloth mother which provided no food, or the wire mother which did.

All the monkeys drank equal amounts and grew physically at the same rate. But the similarities ended there. Monkeys who had soft, tactile contact with their terry cloth mothers behaved quite differently than monkeys whose mothers were made out of hard wire.

The behavioral differences that Harlow observed between the monkeys who had grown up with surrogate mothers and those with normal mothers were;

• They were much more timid.
• They didn’t know how to act with other monkeys.
• They were easily bullied and wouldn’t stand up for themselves.
• They had difficulty with mating.
• The females were inadequate mothers.

These behaviors were observed only in the monkeys left with the surrogate mothers for more than 90 days.

For those left less than 90 days, the effects could be reversed if placed in a normal environment where they could form attachments.

Rhesus Monkeys Reared in Isolation

Harlow (1965) took babies and isolated them from birth. They had no contact with each other or anybody else.

He kept some this way for three months, some for six, some for nine and some for the first year of their lives. He then put them back with other monkeys to see what effect their failure to form attachment had on behavior.

The results showed the monkeys engaged in bizarre behavior, such as clutching their own bodies and rocking compulsively. They were then placed back in the company of other monkeys.

To start with the babies were scared of the other monkeys, and then became very aggressive towards them. They were also unable to communicate or socialize with other monkeys. The other monkeys bullied them. They indulged in self-mutilation, tearing hair out, scratching, and biting their own arms and legs.<!–

In addition, Harlow created a state of anxiety in female monkeys which had implications once they became parents. Such monkeys became so neurotic that they smashed their infant’s face into the floor and rubbed it back and forth.

Harlow concluded that privation (i.e., never forming an attachment bond) is permanently damaging (to monkeys).

The extent of the abnormal behavior reflected the length of the isolation. Those kept in isolation for three months were the least affected, but those in isolation for a year never recovered from the effects of privation.

Conclusions

Studies of monkeys raised with artificial mothers suggest that mother-infant emotional bonds result primarily from mothers providing infants with comfort and tactile contact, rather than just fulfilling basic needs like food.

Harlow concluded that for a monkey to develop normally s/he must have some interaction with an object to which they can cling during the first months of life (critical period).

Clinging is a natural response – in times of stress the monkey runs to the object to which it normally clings as if the clinging decreases the stress.

He also concluded that early maternal deprivation leads to emotional damage but that its impact could be reversed in monkeys if an attachment was made before the end of the critical period .

However, if maternal deprivation lasted after the end of the critical period, then no amount of exposure to mothers or peers could alter the emotional damage that had already occurred.

Harlow found, therefore, that it was social deprivation rather than maternal deprivation that the young monkeys were suffering from.

When he brought some other infant monkeys up on their own, but with 20 minutes a day in a playroom with three other monkeys, he found they grew up to be quite normal emotionally and socially.

The Impact of Harlow’s Research

Harlow’s research has helped social workers to understand risk factors in child neglect and abuse such as a lack of comfort (and so intervene to prevent it).

Using animals to study attachment can benefit children who are most at risk in society and can also have later economic implications, as those children are more likely to grow up to be productive members of society.

Ethics of Harlow’s Study

Harlow’s work has been criticized.  His experiments have been seen as unnecessarily cruel (unethical) and of limited value in attempting to understand the effects of deprivation on human infants.

It was clear that the monkeys in this study suffered from emotional harm from being reared in isolation.  This was evident when the monkeys were placed with a normal monkey (reared by a mother), they sat huddled in a corner in a state of persistent fear and depression.

Harlow’s experiment is sometimes justified as providing a valuable insight into the development of attachment and social behavior. At the time of the research, there was a dominant belief that attachment was related to physical (i.e., food) rather than emotional care.

It could be argued that the benefits of the research outweigh the costs (the suffering of the animals).  For example, the research influenced the theoretical work of John Bowlby , the most important psychologist in attachment theory.

It could also be seen as vital in convincing people about the importance of emotional care in hospitals, children’s homes, and daycare.

Harlow, H. F., Dodsworth, R. O., & Harlow, M. K. (1965). Total social isolation in monkeys . Proceedings of the National Academy of Sciences of the United States of America, 54 (1), 90.

Harlow, H. F. & Zimmermann, R. R. (1958). The development of affective responsiveness in infant monkeys . Proceedings of the American Philosophical Society, 102 ,501 -509.

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A series of experiments conducted by psychologist Harry Harlow in the 1950s and 1960s on rhesus monkeys to demonstrate the importance of care-giving and companionship in social development and cognitive function.

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A psychological model attempting to describe the dynamics of long-term interpersonal relationships between humans.

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Uncovering Harry Harlow’s Contribution to Psychology

Harry Harlow was a groundbreaking psychologist whose work revolutionized our understanding of human behavior. His research on attachment theory, maternal deprivation, and the importance of contact comfort challenged previous beliefs and paved the way for new perspectives in psychology.

His controversial experiments raised ethical concerns and sparked debate about the treatment of animals in research. Despite this, Harlow’s legacy continues to influence modern psychology, making his work as relevant today as it was in his time.

• 1 Key Takeaways:
• 2 Who Is Harry Harlow?
• 3.1 Attachment Theory
• 3.2 Maternal Deprivation Experiment
• 3.3 Importance of Contact Comfort
• 3.4 Social Isolation Studies
• 4.1 Importance of Nurturing and Social Interaction
• 4.2 Criticism of Behaviorism
• 5.1 Animal Welfare Concerns
• 5.2 Human Application of Findings
• 6.1 Influence on Attachment Theory
• 6.2 Impact on Animal Research Ethics
• 6.3 Continued Relevance in Modern Psychology
• 7.1 What were some of Harry Harlow’s key contributions to the field of psychology?
• 7.2 How did Harry Harlow’s research on attachment challenge previous theories?
• 7.3 What was the significance of Harry Harlow’s ‘surrogate mother’ experiments?
• 7.4 How did Harry Harlow’s work influence the field of developmental psychology?
• 7.5 What ethical considerations did Harry Harlow’s research raise in the scientific community?
• 7.6 How does Harry Harlow’s work continue to influence modern psychology?

Key Takeaways:

Who is harry harlow.

Harry Harlow was a prominent psychologist known for his groundbreaking experiments on the nature of love , affection , and attachment in primates, particularly focusing on the significance of maternal care and its impact on the psychological development and behavior of infants.

His research revealed that the absence of maternal care can lead to severe developmental and psychological issues in infant monkeys.

Harlow’s experiments, including the famous surrogate mother studies, demonstrated that the presence of a nurturing mother figure positively influenced the emotional and social well-being of the primates.

These insights emphasized the fundamental importance of secure attachment and the essential role of maternal warmth in shaping an individual’s psychological resilience .

What Was Harlow’s Contribution to Psychology?

Harry Harlow made significant contributions to psychology, particularly in the areas of attachment theory , maternal deprivation , and the understanding of social relationships in primates through his ethical and insightful experiments.

His groundbreaking research on infant rhesus monkeys revealed the profound impact of *maternal deprivation* on their social and emotional development.

Harlow’s experiments, such as the notorious ‘wire mother’ and ‘cloth mother’ studies, demonstrated the paramount importance of attachment and closeness in forming strong social bonds and emotional resilience in primates.

The implications of Harlow’s work extended to the understanding of human psychology, leading to the acknowledgment of the critical role of *caregiver-child relationships* in shaping emotional well-being and social responsiveness.

His findings contributed to the emergence of revolutionary theories that reshaped the way we perceive *parent-child interactions* and the significance of early nurturing experiences in *social development* .

Attachment Theory

Attachment theory, as studied and refined by Harry Harlow and subsequently developed by researchers like John Bowlby and Mary Ainsworth, sheds light on the profound impact of caregivers, emotional connections, and social bonds through Harlow’s pioneering experiments on the significance of maternal touch and care.

Harlow’s experiments with rhesus monkeys revealed that maternal touch and comfort are essential for healthy emotional and social development in the offspring.

These findings highlighted the critical role of nurturing interactions in forming secure attachments. The insights gained from Harlow’s research have provided a solid foundation for understanding the importance of early caregiver-child relationships in shaping an individual’s emotional well-being and capacity for forming meaningful connections throughout life.

Maternal Deprivation Experiment

Harry Harlow’s maternal deprivation experiment , involving the psychological and behavioral observations of infant primates subjected to varying degrees of maternal separation, raised ethical considerations and significantly contributed to the understanding of the critical role of caregivers in early development.

The experiment, which took place in the 1950s and 1960s, revealed that the maternal bond is crucial for the psychological well-being of infants. Harlow’s research demonstrated that the absence of a nurturing mother figure impacted the social and emotional development of the infant primates.

These observations highlighted the importance of emotional connection for healthy cognitive and socio-emotional development, shedding light on the significance of responsive caregiving for human infants as well.

Importance of Contact Comfort

Harry Harlow’s research highlighted the paramount importance of contact comfort in psychology, revealing its profound effects on emotional distress, caregiver interactions, behavioral patterns, and the development of meaningful social relationships.

The concept of contact comfort, central to Harlow’s studies, underscores the significance of tactile and emotional closeness in alleviating emotional distress and fostering psychological well-being.

His experiments with infant rhesus monkeys demonstrated that the provision of soft, comforting materials, such as cloth surrogate mothers, played a crucial role in the monkeys’ emotional stability.

The research also shed light on the fundamental role of contact comfort in shaping caregiver dynamics. Harlow’s findings indicated that the presence of a nurturing, comforting figure positively influenced the monkeys’ behavioral patterns, leading to increased sociability and reduced anxiety.

Harlow’s research offered crucial insights into the intricate process of forming social relationships. The provision of contact comfort was shown to be pivotal in establishing trust, empathy, and emotional connections, forming the foundation for enduring social bonds.

Social Isolation Studies

Harry Harlow’s social isolation studies illuminated the detrimental effects of emotional and psychological deprivation on infants, prompting ethical considerations and raising awareness about the critical role of caregivers in the ethical treatment of animals in research.

Harlow’s experiments with rhesus monkeys revealed that those raised in isolation exhibited severe social and cognitive impairments, underscoring the crucial impact of early social interactions on development.

The studies raised ethical concerns about the treatment of animals in research, leading to advancements in the ethical guidelines for animal experimentation. They emphasized the paramount importance of nurturing care and maternal attachment in ensuring the well-being of infants, shedding light on the vital role of caregivers in fostering healthy emotional and psychological development.

How Did Harlow’s Work Challenge Previous Beliefs?

Harry Harlow’s work challenged previous beliefs by emphasizing the crucial role of nurturing and social interaction in shaping behavior, learning, and cognitive development, thus challenging the traditional behaviorist perspectives on the formation of social relationships.

Harlow’s research with rhesus monkeys highlighted the importance of maternal care and companionship in the development of offspring. Through experiments with surrogate mothers made of wire and terry cloth, he demonstrated the profound impact of a nurturing figure on the monkeys’ behaviors and learning abilities.

This groundbreaking insight into the influence of social interactions on cognitive development revolutionized the field of psychology. It brought about a greater understanding of the crucial role of relationships in shaping human behavior and emotional well-being.

Importance of Nurturing and Social Interaction

Harlow’s findings underscored the critical importance of nurturing and social interaction in psychological, cognitive, and behavioral development, challenging prevailing beliefs about the primary factors influencing the formation of relationships and social behaviors.

His research with rhesus monkeys revealed that attachment was not solely a result of seeking nourishment from the mother but also stemmed from the need for comfort and security.

This highlights the intrinsic role of emotional bonds in shaping social behaviors.

His studies also demonstrated the detrimental effects of social isolation on cognitive development.

This emphasizes the profound impact of social interaction on the formation of cognitive abilities and problem-solving skills.

Criticism of Behaviorism

Harlow’s experiments and findings led to significant criticism of behaviorism, challenging its views on learning, relationships, and the underlying psychological theories that shaped behavioral perspectives in psychology.

The criticism centered around the implications of Harlow’s experiments on the understanding of psychological development and the nature of human behavior.

These experiments raised questions about the limitations of behaviorist theories in explaining complex social behaviors, especially in the context of attachment and emotional bonding .

The findings prompted a shift towards cognitive theories and a greater emphasis on the role of internal mental processes in understanding human behavior and learning.

What Were the Ethical Implications of Harlow’s Experiments?

Harlow’s experiments raised profound ethical implications regarding animal welfare , the potential human application of findings, and the ethical dilemmas surrounding infant development and psychological research.

Such experiments sparked discourse on the ethical treatment of research animals , with concerns about their physical and psychological well-being during testing.

The potential application of the findings to understand human attachment and development requires careful consideration of ethical boundaries and the balance between scientific progress and moral responsibility . These experiments highlighted the ethical dilemmas inherent in conducting research involving vulnerable populations , especially infants , raising questions about informed consent and long-term impacts on subjects.”

Animal Welfare Concerns

Harlow’s experiments raised significant animal welfare concerns , sparking discussions about the ethical nature of research on maternal attachment and its implications for infant development.

The controversial use of primates in these experiments spurred criticism from ethicists, psychologists, and animal rights activists. They questioned the necessity of subjecting animals to psychological distress, particularly in studies exploring the impact of maternal separation on infant behavior. The debate focused on the ethical considerations of using animals as research subjects, raising profound ethical dilemmas regarding the balance between scientific advancement and animal welfare.

The long-term effects of maternal deprivation on infant development became the center of attention, highlighting the ethical responsibilities of researchers to prioritize the well-being of the subjects. These discussions ultimately led to advancements in ethical guidelines for research involving animal subjects. These guidelines emphasize the importance of informed consent , minimizing suffering, and promoting humane treatment .

Human Application of Findings

The potential human application of Harlow’s findings raised ethical dilemmas about the translation of research on caregiver interactions, emotional distress, and psychological theories to human development and the ethical considerations surrounding such applications.

Harlow’s research on caregiver interactions , emotional distress, and psychological development in monkeys has significant implications for understanding human behavior and development.

The ethical dilemmas emerge when considering the translation of such findings to human applications. While the insights may offer valuable understanding for human relationships and emotional well-being, the potential harm and distress caused to subjects in replicating such studies poses ethical concerns.

What Is Harlow’s Legacy in Psychology?

Harlow’s legacy in psychology resonates through his profound influence on attachment theory, ethical considerations in research, and the enduring relevance of his work in shaping modern psychological perspectives, particularly in the sphere of animal research ethics.

His groundbreaking experiments with surrogate mothering in rhesus monkeys revolutionized our understanding of the crucial role of early attachment in psychological development.

Not only did his work provide significant insights into the nature of human bonds, but it also raised pivotal ethical questions regarding the treatment of animals in research.

Harlow’s enduring legacy extends beyond his scholarly contributions; his ethical dilemmas in research methodology have paved the way for stringent ethical guidelines and regulations in psychological experimentation.

This pivotal aspect of his work has helped shape contemporary standards for research ethics, ensuring the humane treatment of subjects and animal welfare.

Influence on Attachment Theory

Harlow’s research exerted a significant influence on attachment theory, challenging the perspectives of behaviorists and reshaping the understanding of the role of caregivers in shaping relationships and psychological theories about attachment.

His pioneering experiments with rhesus monkeys provided evidence that the need for comfort and security supersedes the need for basic sustenance, contradicting behaviorist beliefs at the time.

This work highlighted the crucial role of emotional connections and supportive bonds in human and animal development, fundamentally shifting the paradigm of attachment theory.

Harlow’s findings contributed to the evolution of psychological theories, emphasizing the enduring impact of early relationships on human behavior and emotional well-being.

Impact on Animal Research Ethics

Harlow’s experiments had a profound impact on animal research ethics, prompting more thoughtful ethical considerations about the observation and treatment of social relationships in primate research and the broader context of psychological experimentation.

The insight gained from Harlow’s experiments raised significant concerns regarding the ethical treatment of primates as sentient beings with complex social needs. Researchers were compelled to reevaluate the methods of observing and intervening in primate social relationships, striving to minimize potential harm and distress.

This led to the establishment of ethical guidelines and regulations, emphasizing compassionate and responsible practices in primate research. The ethical discourse expanded to encompass broader implications for psychological experimentation, shaping modern ethical standards in animal research.

Continued Relevance in Modern Psychology

Harlow’s work continues to hold significant relevance in modern psychology, impacting the understanding of emotional distress , the influence of early experiences, and the enduring importance of his contributions to psychological research.

His research on the impact of early experiences on emotional development has paved the way for a deeper comprehension of mental health challenges in later years.

By demonstrating the integral role of attachment in emotional well-being, Harlow’s work remains invaluable in elucidating the profound effects of early relationships on mental health.

His experiments with infant monkey attachment have significantly shaped our understanding of human behavior and the impact of atypical early experiences on emotional distress.

Frequently Asked Questions

What were some of harry harlow’s key contributions to the field of psychology.

Harry Harlow is best known for his groundbreaking research on the importance of attachment and social deprivation in primates. He also made significant contributions to the understanding of learning and motivation, as well as the ethical treatment of animals in research.

How did Harry Harlow’s research on attachment challenge previous theories?

Harlow’s research on rhesus monkeys showed that attachment is not solely based on the provision of food, as was previously thought. Instead, he demonstrated the crucial role of physical contact and comfort in infant-parent relationships, laying the foundation for further studies on attachment.

What was the significance of Harry Harlow’s ‘surrogate mother’ experiments?

Harlow’s experiments with the ‘surrogate mother’ demonstrated the importance of contact comfort and the negative effects of social isolation on infant primates. This research helped to shape our understanding of the critical role of early relationships in development.

How did Harry Harlow’s work influence the field of developmental psychology?

Harlow’s research on attachment and social deprivation in primates had a significant impact on the field of developmental psychology. It challenged previous theories and sparked further studies on the effects of early relationships on human development.

What ethical considerations did Harry Harlow’s research raise in the scientific community?

Harlow’s experiments with primates raised ethical concerns about the treatment of animals in research, particularly in terms of their physical and emotional well-being. This prompted a re-evaluation of ethical standards and guidelines in psychological research.

How does Harry Harlow’s work continue to influence modern psychology?

Harlow’s research on attachment and social deprivation remains highly influential in modern psychology. It has informed our understanding of the critical role of relationships and early experiences in human development, as well as ethical considerations in scientific research.

Dr. Emily Tan is a researcher in the field of psychological assessment and testing. Her expertise includes the development and validation of psychological measures, with a particular interest in personality assessment. Dr. Tan’s work aims to improve the accuracy and ethical application of psychological tests in various settings, from clinical diagnostics to organizational hiring processes.

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Harry Harlow and the Nature of Affection

What Harlow's Infamous Monkey Mother Experiments Revealed

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Adah Chung is a fact checker, writer, researcher, and occupational therapist. 

• Love and Affection
• Harry Harlow's Research on Love
• Wire Mother Experiment
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Impact of Harry Harlow’s Research

Frequently asked questions.

Harry Harlow was one of the first psychologists to scientifically investigate the nature of human love and affection. Through a series of controversial monkey mother experiments, Harlow was able to demonstrate the importance of early attachments, affection, and emotional bonds in the course of healthy development.

This article discusses his famous monkey mother experiments and what the results revealed. It also explores why Harlow's monkey experiments are so unethical and controversial.

Early Research On Love

During the first half of the 20th century, many psychologists believed that showing affection towards children was merely a sentimental gesture that served no real purpose. According to many thinkers of the day, affection would only spread diseases and lead to adult psychological problems.

"When you are tempted to pet your child, remember that mother love is a dangerous instrument," the behaviorist John B. Watson once even went so far as to warn parents.

Psychologists were motivated to prove their field as a rigorous science. The behaviorist movement dominated the field of psychology during this time. This approach urged researchers to study only observable and measurable behaviors.

An American psychologist named Harry Harlow , however, became interested in studying a topic that was not so easy to quantify and measure—love. In a series of controversial experiments conducted during the 1960s, Harlow demonstrated the powerful effects of love and in particular, the absence of love.   

His work demonstrated the devastating effects of deprivation on young rhesus monkeys. Harlow's research revealed the importance of a caregiver's love for healthy childhood development.

Harlow's experiments were often unethical and shockingly cruel , yet they uncovered fundamental truths that have influenced our understanding of child development.

Harry Harlow's Research on Love

Harlow noted that very little attention had been devoted to the experimental research of love. At the time, most observations were largely philosophical and anecdotal.

"Because of the dearth of experimentation, theories about the fundamental nature of affection have evolved at the level of observation, intuition, and discerning guesswork, whether these have been proposed by psychologists, sociologists, anthropologists, physicians, or psychoanalysts ," he noted.

Many of the existing theories of love centered on the idea that the earliest attachment between a mother and child was merely a means for the child to obtain food, relieve thirst, and avoid pain. Harlow, however, believed that this behavioral view of mother-child attachments was an inadequate explanation.

The Monkey Mother Experiment

His most famous experiment involved giving young rhesus monkeys a choice between two different "mothers." One was made of soft terrycloth but provided no food. The other was made of wire but provided nourishment from an attached baby bottle.

Harlow removed young monkeys from their natural mothers a few hours after birth and left them to be "raised" by these mother surrogates. The experiment demonstrated that the baby monkeys spent significantly more time with their cloth mother than with their wire mother.

In other words, the infant monkeys went to the wire mother only for food but preferred to spend their time with the soft, comforting cloth mother when they were not eating.

Based on these findings, Harry Harlow concluded that affection was the primary force behind the need for closeness.

Harry Harlow's Further Research

Later research demonstrated that young monkeys would also turn to their cloth surrogate mother for comfort and security. Such work revealed that affectionate bonds were critical for development.

Harlow utilized a "strange situation" technique similar to the one created by attachment researcher Mary Ainsworth . Young monkeys were allowed to explore a room either in the presence of their surrogate mother or in her absence.

Monkeys who were with their cloth mother would use her as a secure base to explore the room. When the surrogate mothers were removed from the room, the effects were dramatic. The young monkeys no longer had their secure base for exploration and would often freeze up, crouch, rock, scream, and cry.

Harry Harlow’s experiments offered irrefutable proof that love is vital for normal childhood development . Additional experiments by Harlow revealed the long-term devastation caused by deprivation, leading to profound psychological and emotional distress and even death.

Harlow’s work, as well as important research by psychologists John Bowlby and Mary Ainsworth, helped influence key changes in how orphanages, adoption agencies, social services groups, and childcare providers approached the care of children.

Harlow's work led to acclaim and generated a wealth of research on love, affection, and interpersonal relationships. However, his own personal life was marked by conflict.

After the terminal illness of his wife, he became engulfed by alcohol misuse and depression, eventually becoming estranged from his own children. Colleagues frequently described him as sarcastic, mean-spirited, misanthropic, chauvinistic, and cruel.

While he was treated for depression and eventually returned to work, his interests shifted following the death of his wife. He no longer focused on maternal attachment and instead developed an interest in depression and isolation.

Despite the turmoil that marked his later personal life, Harlow's enduring legacy reinforced the importance of emotional support, affection, and love in the development of children.

A Word From Verywell

Harry Harlow's work was controversial in his own time and continues to draw criticism today. While such experiments present major ethical dilemmas, his work helped inspire a shift in the way that we think about children and development and helped researchers better understand both the nature and importance of love.

Harlow's research demonstrated the importance of love and affection, specifically contact comfort, for healthy childhood development. His research demonstrated that children become attached to caregivers that provide warmth and love, and that this love is not simply based on providing nourishment. 

Harlow's monkey mother experiment was unethical because of the treatment of the infant monkeys. The original monkey mother experiments were unnecessarily cruel. The infant monkeys were deprived of maternal care and social contact.

In later experiments, Harlow kept monkeys in total isolation in what he himself dubbed a "pit of despair." While the experiments provided insight into the importance of comfort contact for early childhood development, the research was cruel and unethical.

Hu TY, Li J, Jia H, Xie X. Helping others, warming yourself: altruistic behaviors increase warmth feelings of the ambient environment . Front Psychol . 2016;7:1349. doi:10.3389/fpsyg.2016.01349

Suomi SJ. Risk, resilience, and gene-environment interplay in primates . J Can Acad Child Adolesc Psychiatry . 2011;20(4):289-297.

Zhang B. Consequences of early adverse rearing experience(EARE) on development: insights from non-human primate studies . Zool Res . 2017;38(1):7-35. doi:10.13918/j.issn.2095-8137.2017.002

Harlow HF. The nature of love .  American Psychologist. 1958;13(12):673-685. doi:10.1037/h0047884

Hong YR, Park JS. Impact of attachment, temperament and parenting on human development . Korean J Pediatr . 2012;55(12):449-454. doi:10.3345/kjp.2012.55.12.449

Blum D. Love at Goon Park . New York: Perseus Publishing; 2011.

Ottaviani J, Meconis D. Wire Mothers: Harry Harlow and the Science of Love . Ann Arbor, MI: G.T. Labs; 2007.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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Harlow’s Monkey Experiments: Revolutionizing Developmental Psychology

With a series of groundbreaking experiments that sent shockwaves through the world of developmental psychology, Harry Harlow’s research on rhesus monkeys forever changed our understanding of the critical role that love and affection play in shaping the emotional and cognitive development of infants.

Born in 1905, Harry Harlow was a curious and unconventional psychologist who would go on to challenge the prevailing theories of his time. His work, though controversial, would ultimately revolutionize our understanding of attachment, love, and the importance of early caregiving experiences. Harlow’s experiments, conducted primarily in the 1950s and 1960s, were as groundbreaking as they were unsettling, forcing us to confront uncomfortable truths about the nature of love and its profound impact on development.

Imagine, if you will, a world where the prevailing wisdom suggested that infants formed attachments to their mothers simply because they provided food. It sounds absurd now, doesn’t it? But that was precisely the landscape of developmental psychology before Harlow came along and turned everything on its head. His work would go on to influence generations of psychologists, parents, and policymakers, reshaping our understanding of what it means to nurture a child.

The Cloth Mother vs. Wire Mother: A Tale of Two Surrogates

At the heart of Harlow’s most famous experiment was a deceptively simple question: What drives infant attachment? Is it merely the provision of food, as behaviorists of the time suggested, or is there something more profound at play?

To answer this question, Harlow devised an experiment that would become iconic in the annals of psychology. He created two surrogate “mothers” for infant rhesus monkeys: one made of wire that provided milk, and another covered in soft terry cloth that offered no nourishment. The setup was ingenious in its simplicity, yet the results would prove to be anything but straightforward.

What Harlow observed was nothing short of revolutionary. The infant monkeys, when given a choice, consistently chose to cling to the soft, cloth-covered surrogate, even when hungry. They would only briefly visit the wire mother to feed before returning to the comfort of the cloth surrogate. This preference was so strong that the infants would spend up to 22 hours a day with the cloth mother, only reluctantly leaving to feed.

But Harlow didn’t stop there. He took his experiments further, introducing fear-inducing stimuli to see how the infant monkeys would react. Time and again, the results were clear: when frightened, the infants would rush to the cloth mother for comfort and security, using it as a “secure base” from which to explore their environment.

These findings flew in the face of the dominant behaviorist theories of the time, which posited that infants formed attachments to their mothers simply because they associated them with the reduction of hunger. Harlow’s work suggested something far more profound: that comfort, contact, and affection were not just nice-to-haves, but essential components of healthy development.

The implications of this work for attachment theory were immense. Harry Harlow’s groundbreaking contributions to psychology laid the groundwork for later researchers like John Bowlby and Mary Ainsworth, who would go on to develop attachment theory as we know it today. Harlow’s experiments provided empirical evidence for what many had intuitively felt: that love and affection are not mere luxuries, but fundamental necessities for healthy emotional and cognitive development.

Challenging the Status Quo: Harlow’s Impact on Developmental Psychology

Harlow’s work didn’t just ruffle a few feathers; it sent the entire field of developmental psychology into a tailspin. His experiments challenged the two dominant theories of his time: behaviorism, which reduced all behavior to learned responses, and psychoanalytic theory, which emphasized the role of unconscious drives.

By demonstrating the critical importance of comfort and affection in infant development, Harlow forced psychologists to reconsider their understanding of human behavior and motivation. His work suggested that there were innate needs for love and affection that couldn’t be explained by simple reinforcement or drive reduction theories.

This emphasis on the importance of maternal care and affection had far-reaching implications. It influenced not only psychological theory but also practical approaches to childcare and parenting. Harlow’s work contributed to a shift away from the cold, detached parenting styles that had been advocated by some experts in the early 20th century, towards more nurturing and responsive approaches.

The impact of Harlow’s work on attachment theory cannot be overstated. His experiments provided a crucial empirical foundation for the ideas that John Bowlby would later develop into attachment theory. This theory, which emphasizes the importance of early caregiving relationships in shaping later social and emotional development, has become one of the most influential frameworks in developmental psychology.

Harlow’s research also had a profound impact on child-rearing practices and policies. His work contributed to changes in hospital policies, encouraging more contact between mothers and newborns. It influenced adoption practices, highlighting the importance of providing consistent, loving care to infants and young children. In essence, Harlow’s work helped to humanize our approach to child development, emphasizing the emotional needs of children alongside their physical ones.

Beyond the Cloth Mother: Harlow’s Other Notable Experiments

While the cloth mother vs. wire mother experiment is undoubtedly Harlow’s most famous work, it was far from his only contribution to the field. Harlow conducted a series of other experiments that, while often controversial, provided further insights into social and cognitive development.

One of the most infamous of these was the “pit of despair” experiment. In this study, Harlow isolated infant monkeys in a chamber he called the “pit of despair,” a featureless, stainless-steel vertical chamber designed to produce total social isolation. The results were devastating, with the monkeys showing severe psychological distress and an inability to function socially when later introduced to other monkeys.

Harlow also conducted a series of social isolation studies, where he raised monkeys in total isolation for varying periods. These experiments revealed the profound impact of early social experiences on later behavior and social functioning. Monkeys raised in isolation showed a range of disturbing behaviors, including self-harm, inability to mate, and extreme fear or aggression towards other monkeys.

In an attempt to mitigate some of the damage caused by isolation, Harlow developed “surrogate peers” – inanimate objects designed to provide some form of social stimulation. While these surrogates couldn’t fully replace real social interaction, they did demonstrate that even limited social stimulation could have some positive effects on development.

These experiments, while ethically questionable by today’s standards, provided valuable insights into the importance of social interaction for cognitive and emotional development. They demonstrated that social experiences play a crucial role in shaping not just emotional responses, but also cognitive abilities and problem-solving skills.

The Ethical Quandary: Criticisms and Concerns

It’s impossible to discuss Harlow’s work without addressing the significant ethical concerns it raised. His experiments, particularly those involving social isolation, caused severe psychological harm to the monkey subjects. Many of the monkeys used in his studies showed long-lasting behavioral abnormalities and were unable to integrate into monkey society.

The “pit of despair” experiment, in particular, has been widely criticized for its cruelty. Even Harlow himself later expressed regret about this experiment, stating that it was “the only thing I ever did that I feel ashamed of.”

These experiments sparked intense debate over the balance between scientific value and ethical considerations in research. While Harlow’s work undoubtedly provided valuable insights into development and attachment, many have questioned whether the knowledge gained was worth the suffering inflicted on the animal subjects.

From a modern perspective, Harlow’s methods are generally viewed as unethical and would not be permitted under current animal research guidelines. His work, along with other controversial studies of the mid-20th century, played a significant role in the development of more stringent ethical standards for psychological research.

However, it’s important to note that ethical standards in research have evolved significantly since Harlow’s time. What was considered acceptable then would be unthinkable now. This evolution in ethical standards is, in part, a legacy of Harlow’s work – his experiments forced the scientific community to grapple with difficult questions about the ethics of animal research and the limits of scientific inquiry.

The Enduring Legacy: Harlow’s Impact on Psychology and Beyond

Despite the ethical controversies surrounding his work, there’s no denying the profound and lasting impact of Harlow’s research on psychology and our broader understanding of human development.

His work has had a lasting influence on child psychology and parenting practices. The emphasis on the importance of love and affection in early childhood has become deeply ingrained in our understanding of child development. The mother-child bond, its psychological foundations and lifelong impact , continues to be a central focus of developmental research, building on the foundations laid by Harlow’s work.

Harlow’s contributions to our understanding of love and affection have extended far beyond the realm of infant development. His work has influenced research on adult relationships, helping to shape our understanding of the long-term impacts of early attachment experiences.

In the realm of animal research ethics, Harlow’s work serves as a cautionary tale. While his experiments provided valuable insights, they also highlighted the need for more humane research practices. The ethical debates sparked by his work have contributed to the development of more stringent guidelines for animal research, emphasizing the importance of minimizing harm and considering alternative research methods where possible.

In developmental psychology and neuroscience, Harlow’s legacy continues to shape research directions. His work laid the groundwork for ongoing investigations into the neurobiological basis of attachment, the long-term effects of early experiences on brain development, and the complex interplay between nature and nurture in shaping behavior and cognition.

Conclusion: The Complex Legacy of a Controversial Pioneer

As we reflect on Harry Harlow’s work, we’re confronted with a complex legacy that defies simple categorization. On one hand, his experiments provided crucial insights that revolutionized our understanding of attachment, love, and the importance of early caregiving experiences. His work challenged prevailing theories, reshaped our approach to child development, and laid the groundwork for attachment theory – a framework that continues to influence psychology, education, and childcare practices to this day.

On the other hand, the methods Harlow used to gain these insights were often cruel and would be considered deeply unethical by today’s standards. His experiments caused significant suffering to his animal subjects, raising difficult questions about the balance between scientific progress and ethical considerations.

Perhaps the most enduring aspect of Harlow’s legacy is the way his work has forced us to grapple with these complex ethical issues. His experiments serve as a stark reminder of the potential costs of scientific inquiry and the importance of robust ethical guidelines in research.

Despite the controversies, the relevance of Harlow’s work in modern psychology cannot be overstated. His emphasis on the importance of love and affection in early development continues to influence research and practice in fields ranging from developmental psychology to neuroscience.

As we look to the future of attachment and developmental research, we carry with us the insights gained from Harlow’s work, tempered by a heightened awareness of ethical considerations. Modern researchers continue to explore the intricate dance of genes and environment in shaping development, the neurobiological underpinnings of attachment, and the long-term impacts of early experiences – all while striving to conduct research in ways that respect the wellbeing of both human and animal subjects.

In the end, Harry Harlow’s legacy serves as a powerful reminder of the complex interplay between scientific progress and ethical responsibility. His work forever changed our understanding of love, attachment, and development – a testament to the profound impact that psychological research can have on our understanding of what it means to be human.

References:

1. Blum, D. (2002). Love at Goon Park: Harry Harlow and the Science of Affection. Basic Books.

2. Harlow, H. F. (1958). The nature of love. American Psychologist, 13(12), 673-685.

3. Suomi, S. J., & Leroy, H. A. (1982). In memoriam: Harry F. Harlow (1905-1981). American Journal of Primatology, 2(4), 319-342.

4. Van der Horst, F. C., LeRoy, H. A., & Van der Veer, R. (2008). “When strangers meet”: John Bowlby and Harry Harlow on attachment behavior. Integrative Psychological and Behavioral Science, 42(4), 370-388.

5. Vicedo, M. (2009). The father of ethology and the foster mother of ducks: Konrad Lorenz as expert on motherhood. Isis, 100(2), 263-291.

6. Harlow, H. F., & Zimmermann, R. R. (1959). Affectional responses in the infant monkey. Science, 130(3373), 421-432.

7. Bowlby, J. (1969). Attachment and loss: Vol. 1. Attachment. Basic Books.

8. Ainsworth, M. D. S., & Bowlby, J. (1991). An ethological approach to personality development. American Psychologist, 46(4), 333-341.

9. Singer, P. (1975). Animal liberation. New York Review/Random House. https://www.harpercollins.com/products/animal-liberation-peter-singer

10. Bretherton, I. (1992). The origins of attachment theory: John Bowlby and Mary Ainsworth. Developmental Psychology, 28(5), 759-775.

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Harlow’s Monkey Experiment (Definition + Contribution to Psychology)

Not all experiments in psychology involve humans; nevertheless, those utilizing animals often aim to shed light on human behavior. Harlow's Monkey experiments had a significant impact on psychology, and despite being considered controversial, they remain influential to this day.

What Are Harlow’s Monkey Experiments?

Harlow's Monkey experiments looked at the influence of parental guidance and interaction during early development. Infant monkeys were placed in isolation, away from their mothers. In other experiments, he took infant monkeys away from their mothers but placed them in a cage with “surrogate” mothers.

In both sets of experiments, he found that the monkeys displayed a specific set of behaviors as a response to their unusual upbringing.

Psychology Before Harlow's Monkey Experiments

Harry Harlow, the man behind the monkey experiments, was a psychologist in the first half of the 20th century. At the time, some conflicting ideas were going around about parenting styles.

Early behaviorists didn’t think parents should be so cuddly. Watson told parents that lots of physical affection would slow down their development.

For years, psychology students were taught that B.F. Skinner’s daughter was subject to the behaviorist’s experiments, and she went crazy after being isolated in a glass box for the first year of her life. Skinner said that she was raised just fine in isolation. (Skinner’s daughter refutes some rumors in a Guardian article .)

As time went on, psychoanalysts like Freud theorized that a child’s development was stunted if the mother didn’t provide love and attention in the first year of the child’s life. If a child experienced trauma during this year, they would develop an oral fixation. After all, getting fed was the most important experience in the first year of a child’s life.

There were a lot of different ideas on how to raise a child. And it makes sense that most parents wanted to do the “right” thing.

So psychologists started to build experiments to test some of these theories. Harry Harlow was one of them. But rather than studying children, he studied rhesus monkeys. His experiments were very different from a lot of psychologists at the time. He wanted to focus on the impact of love and basic physiological needs.

What Happened During Harlow's Monkey Experiments?

The monkeys in isolation were separated from other monkeys for 3-12 months. During that time, some would display behaviors to possibly “self-soothe.” Others would self-mutilate. They would circle anxiously and appear to be distressed.

Harlow also studied what happened when these monkeys were placed back in the company of other monkeys. The results were slightly disturbing. They continued to self-mutilate. They couldn’t integrate themselves into society. These isolated monkeys were scared, aggressive, or dumbfounded. Some of the monkeys died after they stopped eating.

Harlow noted that the longer the monkeys stayed in isolation, the harder it was for them to integrate into society.

Monkeys With Wire or Cloth Mothers

So the monkeys were negatively affected by isolation. But Harlow wanted to go further. Why were the monkeys impacted so significantly? Was it solely because of physiological factors, or did love and affection play a role?

To answer these questions, Harlow set up another experiment. He took the infant monkeys away from their mothers and placed them in a cage with two “surrogate” mothers. One of these surrogate mothers was made out of wire. The other was made out of cloth.

In some cages, the wire mother had food for the monkeys. The cloth mother did not. In other cases, the cloth mother had food for the monkeys. The wire mother did not.

Harlow observed that no matter which surrogate mother held the food, the infants would spend more time with the comforting cloth mother. If only the wire mother had food, the monkeys would only go to them when hungry. Otherwise, they would stay in the comfort of the cloth mother.

This doesn’t mean that the monkeys were fully developed socially. When these monkeys were placed back into cages with other monkeys, they didn’t integrate well. They were shy, didn’t stand up for themselves if bullied, and had trouble mating. The monkeys that did become mothers also had trouble raising their monkeys. Harlow believed these behaviors resulted from the events in their infancy.

Attachment Theory and Harlow's Monkey Experiments

Suppose you have ever read anything from relationship experts or counselors. In that case, you might hear this idea: our relationship with our parents influences the partners we pick and the way we go about relationships. Many psychologists have shared variations of this idea. Some of these variations are cringe-worthy, and some are quite helpful.

One variation of this idea is Attachment Theory . This theory describes four different types of attachments that we develop based on our relationship with our parents. We bring this attachment style (secure, anxious, etc.) into adult relationships.

Attachment Theory was the product of studies conducted by John Bowlby and Mary Ainsworth. However, their studies are not the only ones influencing how we view attachment formation. One set of experiments, Harlow’s Monkey experiments, played a role in influencing how we view attachment. Due to the unethical nature of this experiment, it’s not always discussed in a psychology class or discussions about relationships.

Controversy and Other Studies on Attachment

If you think, “Those poor monkeys!” you’re not alone. Many people believed that Harlow’s experiments were unethical. Why would you subject live animals to an experiment that would ultimately traumatize them? Remember, some of these monkeys died early due to starvation caused by anxious behaviors. Did those monkeys need to die for the good of science?

While some say yes, others say no. Not all studies on attachment took such harsh measures. For example, John Bowlby and Mary Ainsworth observed parents and children as parents left the room for a few minutes at a time. You can learn more about these studies, and the Attachment Styles developed as a result of these studies in another video.

Despite the controversy surrounding his experiments, Harlow did positively impact the world of psychology and parenting. The risks he took for studying love and care, when those topics weren’t discussed in psychology, paid off. His work showed the importance of love and affection. Caregivers, parents, and guardians took note. If your parents or grandparents showed you love and affection as a child, you can thank the research of Harry Harlow and other psychologists who studied Attachment and development.

Related posts:

• Dreams Of Monkeys Meaning (12 Reasons + Interpretation)
• Attachment Styles Theory (Free Test)
• John Bowlby Biography - Contributions To Psychology
• Mary Ainsworth (Biography)
• Golden Child Syndrome (Definition + Examples)

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