Animal studies of attachment: Lorenz and Harlow

What is meant by imprinting?

Imprinting is when an animal such as a bird will strongly attach to the first object (usually the mother) that they encounter. The infant animal will then follow this object.

What did Lorenz aim to investigate?

Lorenz aimed to investigate the mechanisms of imprinting.

What method did Lorenz use in his investigation?

Lorenz 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 (control), while Lorenz kept the other half in an incubator beside himself for several hours (experimental). To ensure imprinting had occurred Lorenz put all the goslings together under an upturned box and allowed them to mix.

What results did Lorenz get?

• When the geese hatched, the young birds regarded Lorenz as their mother and followed him accordingly.

• The other group followed the mother goose, these were the first moving objects they saw, during a 12-17 hour critical period after hatching.

• After the critical period, imprinting was unlikely to happen at all.

•  When the box was removed the two groups separated to go to their respective 'mothers' - half to the goose, and half to Lorenz.

What conclusions did Lorenz draw from his experiment?

• The process of imprinting is a strong biological feature of attachment in certain birds, and that imprinting occurs based on the first object rather than on other cues such as scent or sound. It is innate and programmed genetically, it occuring without any feeding taking place.

• This would explain why goslings imprint after a matter of minutes due to their increased mobility; human babies are born immobile and therefore there is less call for them to form an attachment straight away, and so, this develops later (7-9 months). 

• It supports the view that having a biological basis for an attachment is adaptive as it promotes survival. 

• The longevity of the goslings’ bond with Lorenz would support the view that, on some level, early attachment experiences do predict future bonds.

What did Harlow aim to investigate?

Harlow aimed to study the mechanisms by which newborn rhesus monkeys bond with their mothers.

What method did Harlow use in his investigation?

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 only milk from the wire mother & eight monkeys could get milk from the cloth mother. The animals were studied for various lengths of time throughout their lives and were periodically put through stressful/intense situations.

What results did Harlow get?

In both groups, baby monkeys spent almost all of their day with the cloth mother and for those in the second group, they spent around 17h daily with the cloth mother yet only 1h with the wire mother.

When frightened, the babies only ran to the cloth mother for comfort. When in a new environment, only the cloth mother helped to relieve anxiety. There was also evidence of secure base behaviour.

The monkeys were bullied by other monkeys when introduced. When they had their own offspring, they were violent and abusive.

What secondary investigation did Harlow observe?

Then Harlow observed the difference in behaviour between the monkeys who had grown up with surrogate mothers and those with normal mothers. The surrogate mother monkeys were:

1. They were much more timid (though monkeys with access to a cloth mother were less timid than those without, who were very distressed).

2. They didn’t know how to act with other monkeys.

3. They were easily bullied and wouldn’t stand up for themselves.

4. They had more difficulty with mating.

5. The females were more inadequate as mothers.

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.

What conclusions did Harlow draw from his investigations?

“Contact comfort” (provided by the cloth mother was more important than food in the formation of attachment but not sufficient for healthy development.

Being with an attachment figure promotes curious and exploratory behaviours and the early attachments form the basis for later social relationships - including emotional regulation.

Impacts could be reversed in monkeys if an attachment was made before the end of the critical period. However if maternal deprivation lasted 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.

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, they grew up to be quite normal emotionally and socially.

Rhesus macaques and potentially other primates such as humans have a biological need for physical contact and will attach to whatever provides comfort rather than food, going against the behaviourist theory of attachment.

Generalisability of animal studies

There are problems with generalising findings on attachment from animal studies to human infants, as geese are very different in evolutionary terms, and whilst monkeys are similar genetically to humans, there are still significant differences in both biology and cultural/social environments as well as how mentally or socially complex they are. 

Real world applications of animal studies

Knowledge gained from Harlow’s studies has been applied effectively to the early childcare of human infants. For example contact between mothers and babies is encouraged in the first few hours after birth to promote attachment, and social workers investigate cases of infant neglect as they understand the long term damage that can result from this. It has also been argued that the long-term benefit to millions of human infants resulting from Harlow’s research justifies the studies in terms of cost-benefit analysis.

Validity of animal studies

Harlow's monkeys were in a stressful, unnatural condition anyway, so may have acted differently from how they would in the wild.

Ethics of animal studies

There are serious ethical concerns about the level of suffering that primates endures in Harlow’s experiments as he intentionally orphaned infants and subjected them to high levels of stress. The orphaned infants ended up killing their offspring, causing further harm.

Similarly, as Lorenz’s experiment had a permanent and irreversible negative effect on the geese (for example those that imprinted to him were less able to mate with their own kind) so was very unethical.