Harry Harlow, a psychologist, worked at the University of Wisconsin–Madison in 1930. He specialized in infant–caregiver relationships, infant dependency, and needs, as well as social deprivation and isolation. Harlow’s research with rhesus monkeys is widely recognized.

Maternal Surrogates: Food versus Comfort

In 1958, Harlow conducted experiments where he separated infant rhesus monkeys from their mothers. He created two surrogate ‘mothers’ for the infants: one made of metal that provided milk through an artificial nipple but lacked comfort, and the other covered in soft material that offered comfort but no food.

Harlow observed that the first surrogate met the infants’ primary need for food, while the second, despite not providing food, allowed the rhesus infants to cuddle for comfort. When subjected to a loud noise, the frightened rhesus infants sought solace with the second, fluffy surrogate.

Maternal Surrogates: A Safe Base

In later experiments, Harlow (1958) demonstrated that the fluffy surrogate served as a secure base for rhesus infants to explore unfamiliar environments or objects. During these experiments, the infants, accompanied by their fluffy surrogates, were introduced to a new environment, such as a different cage.

The infants displayed exploration behavior, venturing into unfamiliar surroundings and seeking comfort from the surrogate if startled. In contrast, when the infants were placed in the new environment without a surrogate, they exhibited signs of distress, lying on the floor, paralyzed, rocking back and forth, and sucking their thumbs instead of exploring.

Absence of a Maternal Surrogate

Harlow extended his research to examine the development of rhesus monkeys deprived of exposure to a fluffy surrogate or any surrogate, with markedly adverse outcomes.

Rhesus infants raised without any surrogates displayed the same fearful behavior in unfamiliar environments, as described earlier, but with a notable difference – this behavior persisted even when a surrogate was introduced. 

Upon introducing surrogates to these infants at around a year old, they reacted fearfully and aggressively. Continuous rocking, screaming, and attempts to escape their cages were observed.

Fortunately, these behaviors diminished after a few days. Although the infants approached, explored, and clung to the surrogate, their engagement never reached the same extent as observed in infants raised with a fluffy surrogate from a younger age.

Conclusions from Harlow’s Experiments

Contact Comfort 

Studies with monkeys raised by artificial mothers suggest that providing comfort and tactile contact, rather than simply meeting basic needs like food, primarily drives the formation of mother-infant emotional bonds.

Clinging

Harlow concluded that, for a monkey to develop normally, there must be some interaction with an object to which they can cling during the first months of life, which he identified as a critical period. Clinging serves as a natural response, with monkeys running to their usual clinging object in times of stress, suggesting that clinging reduces stress.

Maternal Deprivation

He further stated that early maternal deprivation causes emotional damage, but monkeys could reverse this impact if they formed an attachment before the end of the critical period. However, if maternal deprivation persisted beyond the critical period, exposure to mothers or peers would not be able to alter the emotional damage that had already occurred.

Social Deprivation

Harlow’s findings emphasized that the young monkeys were suffering more from social deprivation than maternal deprivation. When he raised some infant monkeys on their own but provided them with 20 minutes a day in a playroom with three other monkeys, they grew up to be emotionally and socially normal.

Impact Of Harlow’s Research

Harlow’s discovery directly contradicted previous theories on mother-child attachment, such as the psychoanalytic cupboard model, which emphasized the mother’s role in providing nourishment and meeting basic biological needs as the origin of the bond.

His findings also challenged the behaviorist model, which suggested that children become attached to their mothers through positive reinforcement and conditioning resulting from having their biological needs fulfilled. Moreover, Harlow’s research played a crucial role in challenging the prevailing mindset of the time, which believed that excessive physical cuddling and comforting could spoil a baby.

Harlow’s research has assisted social workers in identifying risk factors for child neglect and abuse, such as a lack of comfort, enabling them to intervene and prevent these issues. Studying attachment using animals can also benefit at-risk children, potentially leading to positive economic outcomes as these children are more likely to grow up and become productive members of society.

Ethical Considerations of Harlow’s Experiments

Critics have raised concerns about Harlow’s work, deeming his experiments unnecessarily cruel and of limited value in understanding the effects of deprivation on human infants.

The monkeys in the study clearly suffered emotional harm from being raised in isolation. When placed with a normally raised monkey, they exhibited persistent fear and depression, huddling in a corner.

Despite criticism, some argue that Harlow’s experiment offers valuable insights into attachment and social behavior. During the research, prevailing beliefs linked attachment to physical (such as food) rather than emotional care.

One could argue that the benefits of the research outweigh the costs, despite the animals’ suffering. For instance, it influenced the theoretical work of John Bowlby, a pivotal figure in attachment theory.

Additionally, the research played a crucial role in emphasizing the importance of emotional care in hospitals, children’s homes, and day care, potentially shaping perceptions and practices in these settings.

Summary

Though people considered Harlow’s monkey experiments cruel, it would have been impossible to replicate the same experiments with human infants.

Despite the controversy, Harlow’s research played a crucial role in redirecting attention to the significant role caregivers play in children’s development.

At the time Harlow published his research, the medical community believed that meeting the physical needs of children was sufficient for ensuring their health. According to this view, as long as a child was fed, provided with water, and kept warm and clean, they would develop into a healthy adult.

Harlow’s experiments challenged this belief, demonstrating that it was not entirely accurate. He showed that the emotional needs of infants are vital for healthy development, emphasizing the importance of love, affection, and comfort in helping infants grow into healthy adults.

References

1. Alicia Nortje, Ph. D. (2023). Retrieved from https://positivepsychology.com/harlow-experiment/ 
2. Bonoir, A. (2017). Psychology: Essential thinkers, classic theories, and how they inform your world. Berkeley: Zephyros Press. 
3. By, Mcleod, S., on, U., & 15, J. (2023). Retrieved from https://www.simplypsychology.org/harlow-monkey.html