AQA Syllabus focus:
'Animal studies of attachment, including Harlow and his research into contact comfort.'
Harlow used rhesus monkeys to test what infant attachment depends on. His findings showed that comfort and security are more important than feeding alone in the formation of early attachment.
Harlow’s aim and procedure
Harry Harlow wanted to investigate why infants become attached to a caregiver. At the time, many psychologists assumed that attachment developed mainly because the caregiver provided food. Harlow tested this idea using rhesus monkeys, whose early social development is closer to humans than that of many other animals.
In his best-known studies, baby monkeys were separated from their biological mothers soon after birth and placed with two surrogate mothers:
Photograph of Harlow’s two surrogate “mothers”: a bare wire model and a cloth-covered model. It visually reinforces the key experimental manipulation—separating “food delivery” from “soft tactile comfort”—that allowed Harlow to test what drives attachment behavior. Source
one made of wire
one covered in soft cloth
Different versions of the study varied which surrogate provided milk. This allowed Harlow to test whether the infant would prefer the source of food or the source of comfort.
The researchers observed several behaviors:
which surrogate the monkey spent most time with
which surrogate it ran to when frightened
whether the monkey would explore a new environment
how the absence of a real mother affected later development
Harlow argued that these observations could reveal the basis of attachment more clearly than simply measuring feeding behavior.
Contact comfort is the emotional security and reassurance provided by close physical contact, especially soft, comforting touch.
This concept became central to Harlow’s explanation of why infant monkeys preferred one caregiver over another.
Diagram illustrating an infant macaque choosing the cloth surrogate over the wire surrogate (which has the feeding bottle). The simplified drawing emphasizes the core idea of contact comfort: infants seek soft, reassuring physical contact as a source of security, not just nutrition. Source
Main findings
The clearest finding was that the monkeys spent far more time with the cloth mother than with the wire mother, even when the wire mother was the one that provided milk. This showed that feeding was not the main cause of attachment.
When the monkeys were frightened, they usually ran straight to the cloth mother and clung to it. The cloth surrogate seemed to reduce anxiety and provide a sense of safety. Harlow also found that monkeys were more willing to explore an unfamiliar area when the cloth mother was present nearby. In other words, comfort appeared to give the monkeys confidence.
These findings suggested that attachment serves an important emotional function as well as a biological one.
Harlow also studied the longer-term effects of growing up without a real mother. Monkeys raised with only surrogate mothers often developed serious social difficulties, such as:
abnormal aggression
problems interacting with other monkeys
difficulties mating
poor parenting of their own offspring
These later problems suggested that early attachment experiences are important for normal social and emotional development.
What Harlow’s research showed about attachment
Harlow’s work challenged the idea that attachment is based mainly on food reinforcement. If feeding were the key factor, the infant monkeys should have preferred the wire mother when it provided milk. They did not. Instead, they chose the soft, comforting figure.
This means attachment is not simply a learned response to being fed. Harlow’s monkeys appeared to need:
comfort
protection
physical closeness
emotional security
The studies therefore support the view that attachment is an affectional bond rather than just a feeding relationship. Harlow’s research also helped psychologists see that early care involves more than meeting physical needs. A caregiver must also provide warmth, reassurance, and responsive contact.
The findings had wider practical influence because they encouraged greater attention to the quality of emotional care given to infants in hospitals, nurseries, and child care settings. Soft touch and stable comfort were seen as psychologically important, not merely optional extras.
Evaluation of Harlow’s research
One strength of Harlow’s work is that it was carried out under highly controlled laboratory conditions. Because he could manipulate whether food came from the cloth or wire mother, he could test cause and effect more clearly than in natural observations. This made the findings about contact comfort convincing.
Another strength is the study’s practical value. It changed ideas about infant care by showing that emotional comfort matters. This helped challenge care practices that focused only on physical needs while ignoring affection and close contact.
However, the research raises serious ethical issues. The monkeys experienced separation, fear, and lasting social disturbance. Some developed severe emotional problems, which means the level of distress was very high. Even if the research was influential, many psychologists argue that the suffering caused was too great to justify.
A further limitation is that evidence from monkeys does not automatically apply fully to humans. Although rhesus monkeys are more similar to humans than birds or dogs, human attachment is influenced by language, culture, and more complex social relationships. This means we should be cautious about making direct one-to-one comparisons.
At the same time, the use of monkeys can also be seen as a strength because their social behavior and need for close caregiving make them more relevant to human attachment than many other animal species. This gives the findings more value than studies using less comparable animals.
Overall, Harlow’s research remains important because it provided strong evidence that contact comfort is a key part of attachment, while also showing the major ethical problems that can arise in animal research.
Practice Questions
Outline one finding from Harlow’s research into attachment. (2 marks)
1 mark for identifying that infant monkeys preferred the cloth-covered surrogate mother.
1 mark for linked detail, such as spending more time with the cloth mother, going to it when frightened, or showing that comfort was more important than food.
Maximum 2 marks.
Discuss Harlow’s research into attachment. (6 marks)
AO1 up to 3 marks:
Harlow used rhesus monkeys separated from their biological mothers.
The monkeys were given wire and cloth surrogate mothers.
The monkeys preferred the cloth mother, especially when frightened, showing the importance of contact comfort.
AO3 up to 3 marks:
Controlled laboratory conditions increased internal validity.
The research had useful applications for child care and understanding emotional needs.
The studies were highly unethical because they caused distress and long-term harm.
Generalizability to humans is limited because human attachment is more complex.
FAQ
Rhesus monkeys were chosen because their early social development is relatively similar to that of humans compared with many other animals.
They:
form close bonds with caregivers
show strong clinging behavior as infants
develop social relationships that can be observed over time
This made them a useful species for studying how attachment forms and what happens when it is disrupted.
Harlow used different conditions to rule out a simple feeding explanation.
If the infant always preferred the soft cloth mother, even when the wire mother provided milk, that meant attachment could not be explained by food alone.
This design made the evidence for contact comfort much stronger because it tested two competing explanations directly.
The frightening stimulus was used to see which surrogate the infant treated as a source of safety.
A true attachment figure should provide comfort under stress, not just during ordinary conditions.
When the monkeys consistently ran to the cloth mother after being scared, Harlow argued this showed that attachment involves protection and emotional reassurance, not just feeding.
His research weakened the claim that attachment develops mainly because the caregiver reduces hunger.
This mattered because older approaches often treated feeding as the central reason babies bond with adults.
Harlow’s results suggested that:
touch matters
comfort matters
the emotional quality of care matters
That shifted the focus from simple reinforcement to the infant’s need for security.
This means the monkeys seemed more confident when the cloth mother was nearby.
They would move away to inspect the environment, then return when uncertain. Without that comforting presence, they were less likely to explore.
This pattern suggests that attachment can support curiosity as well as comfort, because feeling safe allows the infant to engage with the world more confidently.
