Animal Studies of Attachment

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Harlow

AO1

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 socialisation. What, exactly, though, was the basis of this bond?

The behavioural theory of attachment would suggest that an infant would form an attachment with a carer that provides food. In contrast, Harlow's explanantion was that attachment develops as a result of the mother providing comfort, suggesting that infants have an innate need to touch and cling to something for emotional comfort.

Procedure

16 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 towelling cloth.

Eight of the monkeys could get milk from the wire mother.

Eight of the monkeys could get milk from the cloth mother.

The animals were studied for various length of time.

Results

Both groups of monkeys spent more time with the cloth mother (even if the wire mother was the one with the milk). The infants of the first group would only go to the wire mother when hungry. Once fed they 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. The infant would explore more when the cloth mother was present.

Then Harlow observed the difference in behaviour between the monkeys who had grown up with the surrogate mothers and those with normal mothers. They found that:

They were much more timid.

They didn't know how to behave with other monkeys and could be aggressive.

They had difficulty with mating.

The females were "inadequate" mothers - some even killing their offspring.

These behaviours were observed only in the monkeys who were 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.

Harlow concluded that "contact comfort" (provided by the cloth mt=other) was more important than food in the formation of attachment. This also shows that contact comfort is preferable to food but not sufficient for healthy development.

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 until 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.

AO3

Harlow's work has been criticised. 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.

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's experiment is sometimes justified as providing a valuable insight into the development. 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 day care.

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Lorenz's Imprinting Theory

A01

Lorenz (1935) took a large clutch of goose eggs and kept them until they were about to hatch out. Half of the eggs were then placed under a goose mother, while Lorenz kept the other half 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 is known as imprinting, and suggests that attachment is innate and programmed genetically.

Imprinting has consequences, both for short term survival, and in 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 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 occur 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.