Research With Monkeys: Understanding Different Theories of Attachment Relating to Infants


In this essay I am going to evaluate two groups of well-known theorists that explain the development of infant attachment to parents or surrogates. The first theory is called Harlow and Zimmerman, the second one is Ainsworth and Bell. Attachment is a type of bond that develops between one person and another, these theories explain this through various experiments and research.

Harlow and Zimmerman

The Harlow and Zimmerman theory is a study about new born monkeys and the bonding process with their mother. The theorists were watching to see how the monkeys bond to their mum. They discovered that they were dependent on the mothers for protection, nutrition and comfort. Harlow and Zimmerman’s theory suggests that the monkeys physically needed to grasp onto a living being or object for comfort. After carrying out various experiments by separating monkeys, it was determined that if an attachment bond is not formed between the monkey and its mother, it will emotionally damage the cognitive ability, emotional response and behaviour of the monkeys that are being isolated. The attachment bond is usually formed based on physiological needs such as food, and emotional needs too such as affection. This bond will develop from birth and the monkey will become attached to the mother to satisfy its needs.

The theory looked into the behavioural differences that the monkeys faced when growing up with a surrogate rather than its birth mother. The effects were sexual difficulties, low confidence against bullies or for any difficult / challenging situations. It also affected their socialisation and they found it difficult to socialise with their own species. Harlow and Zimmerman concluded that during the first few months of a monkey’s life, they need to have interaction with another of its species in order to develop fully.

The problem with this experiment was that when the monkeys were old enough, they were put into even smaller rooms with many other monkeys. When the experiment was over Harlow decided to make the female monkeys have intercourse against their will, when the new generation was born the new mothers didn’t bond with the monkeys and because of this, some newborn`s were killed by the mothers because the mothers were petrified of bonding with a product of rape.

In my personal opinion, I agree that an infant doesn’t need to have its biological mother to look after them but to some extent; it can affect the child not having the birth mother to comfort them and to protect them against anything that might cause them harm. Harlow and Zimmerman’s research has concluded this as they discovered that there were physiological and emotional effects on the monkeys when in faced with stressful situations such as separation from their birth mother.

Ainsworth and Bell

In 1969 John Bowlby preached about attachment being an “all or nothing process.” (Bowlby, n.d.). This shows that it was one or another. Mary Ainsworth did an experiment showing the attachment regarding children and how it varies overtime between child. She called this the “strange situation classification” (Ainsworth, n.d.) (SSC). Mary Ainsworth decided to experiment with infants between the ages of 12-18 months old; she was challenging the infant’s behaviour in different situations. Theses stages included mother and baby alone, infant being left alone completely and the infant being left alone with a stranger with no supervision from the mother.

Mary revealed different behaviours types and these were exploratory behaviours, search behaviours and affect displays negative. She found out that type B attachment styles were insecure, type A were resistant/ insecure and type C were early interactors with the birth mother.

Mary’s final statement based on her findings was; “caregiver sensitivity hypothesis” (Ainsworth, n.d.). The children’s attachment was intertwined with the behaviour of the birth mother.

In my opinion, I agree that when the infant was left alone, it would cause it to suffer with emotional distress to make its feeling clear that it don’t know the stranger to have an emotional connection with them. This is normal as infants can’t handle difficult situations because their mental capacity is not yet fully developed and matured. On the other hand, if the infant has bonded with the mother and she’s there with the infant whilst a stranger is present, they will have the strength to turn this negative into a positive because of the bond between them.


In this essay I hoped to evaluate two groups of well-known theorists that explain the development of infant attachment to parents or surrogates through various experiments and research. It is clear that from both of the theories, a bond is developed between the infant and parent and if this bond is broken, it can have emotional and psychological effects. Ainsworth’s theory studies the hypothesis in more detail by placing the infant in different situations and then assessing their reaction whereas Harlow and Zimmerman’s theory focuses mainly on separating the monkey from its mother or surrogate .I hope you found this enlightening and informative.


  • Ainsworth, M., n.d. Simply Psychology. [Online]
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  • [Accessed 23 11 2018].
  • Bowlby, J., n.d. simply psychology. [Online]
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  • [Accessed 23 11 2018].
  • harlow, n.d. Exploring yourmind. [Online]
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  • [Accessed 24 11 2019].
  • Zimmerman, H. a., 1958. Simply Psychology. [Online]
  • Available at: https://www/
01 August 2022
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