AIMS: Harry Harlow studied the behaviour of infant monkeys separated from their mothers at birth to see what effects the separation would have on their later behaviour.

He first separated newborn rhesus monkeys from their mothers and raised them in cages on their own, each cage containing a ‘baby blanket’. The babies became extremely distressed whenever the blanket was removed, in a similar way to how monkeys normally do when separated from their mothers. From this, Harlow reasoned that attachment wasn’t based on association with food. His next experiment was to test this hypothesis.

PROCEDURE (METHOD): 8 infant rhesus monkeys were taken from their mothers shortly after birth and kept separately in a cage with two substitute mothers - a ‘cloth mother’ covered with a soft blanket and a skeletal ‘wire mother’. Both ‘mothers’  were of the same size and shape as an adult monkey. For 4 of the 8 monkeys the wire mother incorporated their feeding bottle; for the other 4 the cloth mother had it. The monkeys were kept in these conditions for a period of time and then released into a cage with a group of normally reared monkeys.

To see how the monkeys would react when frightened, Harlow put a teddy bear drummer toy into the cage.

RESULTS (FINDINGS): The infant monkeys preferred to spend time with the cloth mother even when they got their food from the wire mother. The monkeys all ran to the cloth mother when they were frightened by the teddy bear drummer.

When returned to the company of other monkeys, Harlow’s monkeys showed signs of inappropriate social behaviour and delinquency. They were aggressive or indifferent towards other monkeys, unable to form normal relationships; the males were unable to mate successfully and the females attacked any male that tried to mate with them. If they did have offspring, the privated monkeys were extremely poor, neglecting mothers. (The first one to have a baby ignored it and pushed it away when it tried to make contact.

CONCLUSIONS: Firstly, it seems the privated monkeys suffered emotionally, resulting in delinquent and anti-social behaviour.

Harlow concluded that the infant monkeys had an innate need for contact comfort.

Secondly, the study seems to contradict theories that the infants attach for food. Gavin Bremner (1994) describes these findings as inconsistent with Secondary Drive Theory. Harlow  drew the conclusion that comfort and security formed the basis for attachment, rather than food.

EVALUATION (CRITICISMS):

• The Harlow studies were used to support John Bowlby’s hypothesis of Maternal Deprivation. However, Stephen Suomi & Harlow (1972) found that the effects of this privation were not totally irreversible. They found it was possible to socialise 6-month-old isolated monkeys by introducing female monkeys 3 months younger than themselves (monkey therapists!) - with delinquent and stereotypical behaviours becoming much reduced. This therapeutic effect was repeated by Melinda Novak & Harlow (1975), this time keeping the newborn monkeys in total isolation for a year.
• Harlow’s research has been extensively criticised on ethical grounds. However, Harlow argued that the benefits in terms of knowledge far outweighed the ethical problems.
• Care must be taken in generalising Harlow’s rhesus monkey studies to human beings since even the higher mammals appear unable to learn by reflection in the way humans can.

Note #1: This study was just one in a range of studies Harlow conducted both before and after 1959 into the nature of attachment using rhesus monkeys - eg:-

• Also in 1959 Harlow & Robert Zimmermann placed one group of infant rhesus monkeys in a cage with both a cloth mother and a food-providing wire mother while another group could access only a food-giving wire monkey. At the end of their isolation, those monkeys which had had access to the cloth mother were better adjusted physically and psychologically.

Harry Harlow 1959

• With second wife Margaret (1962) he raised some monkeys in total isolation and some with the cloth mother. Those raised in total isolation engaged in bizarre behaviour such as clutching their own bodies and rocking compulsively. When placed back in the company of other monkeys, they were withdrawn and fearful - though they often became aggressive towards both others and themselves, biting their own arms and legs. The extent of the abnormal behaviour reflected the length of the isolation. Meanwhile those raised with the cloth mother were much more able to engage in social activity.
• In another experiment Harlow raised 4 young monkeys without any ‘mother’. They spent the first few months just huddled together but gradually they developed more independence and, in the long term, appeared to have suffered no permanent ill effects.

After Margaret died in 1970, Harlow remarried first wife Clara Mears in 1971 - after which his studies into social deprivation of his monkey participants became increasingly criticised on ethical grounds.

Note #2: Among Harlow’s early uncredited assistants was Abraham Maslow, developer of the Hierarchy of Needs.