Attachment - Animal Studies of Attachment

Two studies that are important for you to know and understand were conducted by Harlow (1958) and Lorenz (1935).

Make sure you can explain the aims, procedures and findings of each of these experiments and make sure you can evaluate the findings of each of them fully.

Harlow's Monkeys (1958)

Harlow wanted to study the mechanisms by which newborn rhesus monkeys bond with their mothers. These infants were highly dependent on their mothers for nutrition, protection, comfort and socialization. What, exactly, though, was the basis of the bond?

The behavioral theory of attachment would suggest that an infant would form an attachment with a carer that provides food.

In contrast Harlow’s explanation was that attachment develops as a result of 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:

1. Infant monkeys reared in isolation – some died, others were frightened and behaved in an abnormal manner. They could not interact with other monkeys even when they were older.

2. Infant monkeys reared with surrogate mothers – 8 monkeys were separated 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. Four of the monkeys could get milk from the wire mother and four from the cloth mother. The animals were studied for 165 days.

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 youngsters fear. The infant would explore more when the cloth mother was present. This supports the evolutionary theory of attachment, in that it is the sensitive response and security of the caregiver that is important (as apposed to the provision of food).
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.
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.

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.

Ethics in Harlow's research.. ethics and applications....

Harlow’s 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 had created a state of anxiety in female monkeys which had implications once they became parents. Such monkeys became so neurotic that they even harmed their own infants.

Harlow's experiment is sometimes justified as providing a valuable insight into the development of attachment and social behaviour. At the time of the research there was a firm 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 may also have helped convince people about the importance of emotional care in hospitals, children's homes and day care.

Make sure you understand the aims and findings of Harlow's research. Here's a quick reminder......

His findings challenge the view that bonds are formed as a result of behavioural learning (reinforcement through food).

Instead the findings suggest that it is social and emotional reward that infants need - not simply food or nourishment.

Lorenz - Imprinting (1935)

Lorenz (1935) took a large clutch of goose eggs and kept them until they were about to hatch. Half of the eggs were then placed under a goose mother (a real one), while Lorenz kept the other half incubated and beside himself for several hours.

When the geese hatched Lorenz imitated a mother duck's quacking sound, upon which the young birds regarded him as their mother and followed him accordingly. The other group followed the mother goose.

Lorenz found that geese follow the first moving object they see, during a 12-17 hour critical period after hatching. This process is known as imprinting and suggests that attachment is innate and programmed genetically, biologically instead of being a result of learning.

Imprinting has consequences, both for short term survival, and in the longer term forming internal templates for later relationships. Imprinting occurs without any feeding taking place. If no attachment has developed within 32 hours it’s unlikely any attachment will ever develop.

To ensure imprinting had occurred Lorenz put all the goslings together under an upturned box and allowed them to mix. When the box was removed the two groups separated to go to their respective 'mothers' - half to the goose, and half to Lorenz.
Imprinting does not appear to be active immediately after hatching, although there seems to be a critical period during which imprinting can occur.

Hess (1958) showed that although the imprinting process could occur as early as one hour after hatching, the strongest responses occurred between 12 and 17 hours after hatching, and that after 32 hours the response was unlikely to occur at all.

Lorenz and Hess believe that once imprinting has occurred it cannot be reversed, nor can a gosling 'imprint' on anything else.