Animal Studies of Attachment

Research on attachment has not been limited to human participants. Some of the most influential studies in attachment theory were conducted using animal subjects — particularly geese and rhesus monkeys. These studies have provided crucial insights into the nature of attachment, the mechanisms underlying bond formation, and the consequences of disrupted early relationships. However, they also raise significant ethical and methodological questions about generalising animal findings to humans.

Key Definition: Imprinting is a form of attachment observed in some species (especially birds) in which the young animal forms an attachment to the first moving object it encounters during a critical period shortly after birth or hatching.

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Lorenz's Research on Imprinting (1935)

Konrad Lorenz (1935) conducted a classic study of imprinting using greylag geese. He divided a clutch of goose eggs into two groups. One group was hatched naturally by the mother goose, while the other group was placed in an incubator so that Lorenz himself was the first moving object the goslings encountered.

Procedure and Findings

The incubator-hatched goslings followed Lorenz everywhere, while the mother-hatched goslings followed the mother goose. When the two groups were mixed together and then released, the goslings immediately divided into two groups — those that followed Lorenz and those that followed the mother goose.

Lorenz identified several key features of imprinting:

Feature	Description
Critical period	Imprinting must occur within a restricted time window, which Lorenz suggested was within hours of hatching (the first 12–17 hours in geese). If no attachment was formed during this period, it would not occur at all.
Irreversibility	Once imprinting had occurred, it could not be reversed. The goslings did not later switch their attachment to the mother goose or any other object.
Sexual imprinting	Lorenz observed that imprinting also affected mate choice in adulthood. Animals that imprinted on a member of another species (or on a human) would later attempt to mate with that species rather than their own.

A Remarkable Case Study

Lorenz described the case of a peacock that had been reared in the reptile house of a zoo. The peacock had imprinted on the giant tortoises during its critical period. In adulthood, it directed its courtship displays exclusively towards giant tortoises, completely ignoring peahens. This case powerfully illustrates the lasting effects of sexual imprinting.

Exam Tip: When evaluating Lorenz's work, remember that imprinting in birds is a very different process from attachment in humans. Imprinting is rapid and tied to a brief critical period; human attachment develops gradually over months. Be cautious about drawing direct parallels.

Evaluation of Lorenz's Research

Strengths:

• The study provides strong evidence for the existence of a critical period in attachment formation in some species.
• The concept of imprinting has been supported by subsequent research on various bird species.
• Lorenz's observations were detailed and systematic, forming the basis of ethology (the scientific study of animal behaviour in natural settings).

Limitations:

• The findings may have limited generalisability to human attachment. Imprinting in birds is a rapid, innate process, while human attachment develops over months and involves complex cognitive and emotional processes.
• Lorenz conducted much of his research through naturalistic observation without rigorous experimental controls, which limits the conclusions that can be drawn about cause and effect.
• Guiton (1966) found that chickens that had imprinted on yellow rubber gloves could later learn to prefer mating with other chickens, challenging Lorenz's claim that imprinting is always irreversible. This suggests that imprinting may be more flexible than Lorenz proposed.

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Harlow's Research on Rhesus Monkeys (1958)

Harry Harlow (1958) conducted a series of experiments on rhesus monkeys that fundamentally challenged the dominant learning theory (cupboard love theory) of attachment, which claimed that infants attach to the person who feeds them.

The Wire Mother vs. Cloth Mother Experiment

Harlow created two surrogate mothers for infant rhesus monkeys:

• Wire mother: Made of bare wire mesh, in some conditions fitted with a feeding bottle providing milk.
• Cloth mother: Made of wire mesh covered in soft terry cloth, but offering no food.

Sixteen infant monkeys were used. In one condition, the wire mother provided food; in the other, the cloth mother provided food.

Key Findings

Observation	Result
Time spent with each mother	Regardless of which mother provided food, the infant monkeys spent significantly more time clinging to the cloth mother. Monkeys with a feeding wire mother still spent up to 22 hours a day on the cloth mother and visited the wire mother only briefly to feed.
Response to a frightening stimulus	When a mechanical, noisy teddy bear was placed in the cage, the infant monkeys ran to the cloth mother for comfort (a secure base), regardless of which mother provided food.
Exploration	Monkeys with a cloth mother explored the environment more confidently, returning to the cloth mother periodically (using her as a secure base). Monkeys raised with only a wire mother showed little exploration and appeared distressed.

Key Definition: Contact comfort is the need for physical, tactile contact with a soft, warm caregiver. Harlow's research demonstrated that contact comfort, not food, is the primary basis for attachment.

The Critical Period and Long-Term Effects

Harlow also investigated the effects of maternal deprivation on later social development. He found that:

• Monkeys raised in total isolation for the first 90 days of life could recover socially if then exposed to peers.
• Monkeys isolated for six months showed severe and lasting social abnormalities.
• Monkeys isolated for 12 months were virtually unable to recover and displayed severe behavioural disturbances including self-harm, social withdrawal, and an inability to interact with other monkeys.