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Animal Studies of Attachment

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Animal Studies of Attachment

This article looks at animal studies in psychology and gives an outline of the procedure used in main studies of animal attachment. It also describes the animal studies of attachment by Lorenz (1935) and Harlow (1958).

Animal studies in psychology are conducted on non-human species to learn more about how humans function. Some animals are used frequently because of the similarity of their brain makeup to humans. For example, common animal subjects include monkeys, mice, and rats. Thus, the purpose is to generalise the findings and knowledge to humans.

Animal studies tend to be conducted on non-human species rather than humans for ethical and practical reasons. Some animals have a short gestation period, and because they reproduce more quickly, researchers can look at the results over more than one generation of animals.

To understand the effects of attachment on humans, researchers often experimented on animals to see how their behaviour was affected. They then made generalisations to humans (which is not without its problems, but more on that later). However, this allowed us to test theories that would be unethical in humans.

The study of animals in psychology is also called comparative psychology.

Animal studies of attachment study early life experiences and attachment formation in animal subjects. They look at the formation of early bonds between animal parents and their offspring. Psychologists find this interesting as attachment is common to various species; therefore, animal studies can help us understand attachment in humans.

Animal Studies of Attachment Similarities between animal and human brains StudySmarter

Similarities between the brain structures of mice, monkeys, and humans.

Animal studies of attachment Similarities in brain structure of a human and mouse StudySmarter

Due to similarities in brain structure, researchers use animals to understand humans.

Animal studies of attachment – Lorenz's research (1935)

In the early 20th century, some ethologists conducted animal studies on the relationships between animal infants and mothers. Their observations influenced psychologists' understanding of attachment in humans. One of the best-known ethologists was Konrad Lorenz.

Lorenz's findings suggest that animal infants have a natural and biological tendency to form attachments to a single subject. The subject is the first moving subject that young animals see after birth or hatching. Lorenz called this process imprinting, which we go into more detail below based on his 1935 study of infant goslings.

How was Lorenz's research in animal studies of attachment conducted?

Here we describe Lorenz's animal studies of attachment using infant goslings. The results of this research and Harlow's 1958 study were essential to our overall understanding of attachment.


Imprinting is the term that describes the biological tendency of infants to form attachments to the first subject they see after birth or hatching. Lorenz first observed the phenomenon of imprinting when he was an infant, and a neighbour gave him a newly hatched duckling that followed him everywhere. Later, he studied animals to see if they imprinted on a single subject.

What were the aims of Lorenz's research?

Lorenz wanted to test imprinting to see if animal infants bond with the first subject they meet. He tested the imprinting theory on some goose eggs in a controlled procedure.

What was the procedure of Lorenz's research?

Lorenz set up a classic experiment in which he randomly divided a clutch of goose eggs. Half of the eggs hatched with the mother goose in their natural environment. Lorenz kept the other half in an incubator, where they would see him as soon as they hatched.

When the eggs hatched from the incubator, Lorenz made a sound imitating a mother goose and then recorded the behaviour of the young.

Lorenz then tagged all of the goslings to determine whether they came from the naturally hatched eggs or the incubated eggs. He mixed both groups of goslings and placed them under an upturned box. Lorenz then removed the box and recorded the behaviour. Through this method, he tested whether imprinting had taken place.

Findings of Lorenz's research in animal studies of attachment (1935)

Once he lifted the box, half the goslings ran to their mother goose and the other half to Lorenz. The goslings that ran to Lorenz were, indeed, in the controlled incubator group. The goslings that ran to their mother had hatched in her presence.

This phenomenon is called imprinting, whereby bird species that are mobile from birth (like geese and ducks) attach to and follow the first moving subject they see. Research suggests that attachment is innate and biologically programmed.

Lorenz also identified a critical period in which imprinting must occur. Depending on the species, this can be as early as 12-17 hours after hatching (or birth). Lorenz notes that the infants will not attach to a mother figure if imprinting does not occur within that time.

Lorenz also believed that imprinting could not be undone. Once the infant imprinted, they could not imprint on anything else. Later research supported this theory and showed that imprinting was probably impossible 32 hours after hatching. The research also found that the strongest imprinting responses occurred between 12 and 7 hours after hatching but could occur as early as one hour after hatching.

Animal studies of attachment Lorenz research goslings StudySmarter

Lorenz with his imprinted goslings during his study in 1935. The goslings can be seen trailing behind Lorenz.

Lorenz's observation of sexual imprinting

Lorenz observed that birds imprinted on humans later exhibited courtship behaviour towards humans. In his 1952 case study, Lorenz described a peacock reared in a zoo's reptile house. The first moving subjects the peacock saw after hatching were giant tortoises. Once fully grown, this bird would direct courtship behaviour only towards giant tortoises. Lorenz concluded that this meant it had undergone sexual imprinting.

Further research used baby chicks imprinted on a yellow rubber glove that fed them during a critical development period. Later on, the chicks attempted to initiate sexual activity with the rubber glove. This research supports the findings of Lorenz's original 1935 study by suggesting that imprinting is a long-lasting effect. The imprinting process affects the sexual behaviour of the chicks, known as sexual imprinting.

Animal studies of attachment Harlow's research (1958)

Another prominent ethologist was Harry Harlow, who studied attachment in rhesus monkeys. His research contributed significantly to our understanding of attachment, as the monkeys he used were more similar to humans.

Harlow's findings suggest that providing comfort is more important than providing food in establishing attachment.

How was Harlow's research in animal studies of attachment conducted?

We will now describe Harlow's animal studies of attachment with baby rhesus monkeys. It is essential to understand why the findings of this research and Lorenz's 1935 study are crucial to our overall understanding of attachment.

Contact comfort

Harlow found that baby monkeys actively sought to spend more time with something that gave them comfort. Monkeys that received only food, but no comfort, suffered from long-term social and emotional damage.

What was the procedure of Harlow's research?

Harlow used baby monkeys he had separated from their biological mothers within hours of birth. He placed these monkeys in a room with 'surrogate' mothers; one made of mesh wire and the other made of wood and covered with a soft cloth. The surrogate mothers were the same size and could feed the monkeys with a milk dispenser.

In the first experiment, Harlow placed all the monkeys with both surrogate mothers to choose which 'mother' they wanted to go to. In the second experiment, he divided monkeys into two groups, each with a surrogate mother.

Animal studies of attachment Harlow monkey experiment StudySmarter

The surrogate mothers in Harlow's study. A rhesus monkey is seeking comfort from the clothed surrogate mother.

Findings of Harlow's research (1958)

  1. In the first experiment, the monkeys could choose which mother they wanted to go to. Harlow found that the baby monkeys spent more time with the surrogate 'mother' with the cloth around them, cuddling it, although both mothers supplied the same amount of food.
  2. In the second experiment, the monkeys had no choice of mother. Harlow found that the baby monkeys with the clothed surrogate mother showed healthy and normal emotional attachment despite receiving the same amount of food. One example is that they would come near the surrogate mother and cuddle with her when they feel stressed or threatened.

The monkeys with a surrogate mother made of mesh wire did not behave the same way. When faced with the same level of stress or threat, they threw themselves on the floor, rocked back and forth, and did not seek comfort from their surrogate mother.

The results suggest that the monkeys spent most of their time with the cloth-covered mother, providing comfort through contact. The experiments also showed that meeting physical needs, such as food, was insufficient to form a mother-infant bond.

Maternal deprivation

The monkeys deprived of their mothers suffered long-term and irreversible social and emotional damage as adults. Monkeys deprived of a mother-like figure failed to develop healthy and functioning social behaviours.

These results suggest that human children may also suffer from long-term emotional damage if they do not have an attachment figure.

The critical period for normal development

Like Lorenz, Harlow concluded that there is a critical period for forming an attachment. An infant monkey had to be introduced to a mother figure within 90 days to form an attachment. After this time, bonding was no longer possible, and the damage done by early deprivation became irreversible.

Evaluation of Lorenz's and Harlow's research in animal studies of attachment

While Lorenz's and Harlow's findings were significant in many ways, they were also subject to considerable evaluation.

Strengths of the research:

  • Later research corroborated Lorenz's findings of imprinting and long-term effects.
  • Monkeys and humans are similar in that they have the same brain structure. From this perspective, Harlow's research will likely help us better understand human behaviour.
  • Harlow's research yielded valuable practical applications for attachment and the importance of emotional support in early child development. His work influenced John Bowlby, an influential psychologist who studied attachment theory in human children. His findings may outweigh the harm done to monkeys.
  • Studying animals avoided ethical problems that arise when studying humans. It is highly unlikely that Lorenz and Harlow would have been able to separate human infants from their mothers in the same way.

Weaknesses of the research:

  • Lorenz's research may not apply to humans because birds are not similar to humans.
  • Lorenz's and Harlow's research is unethical because of the long-term effects on their animal subjects. In Harlow's case, the monkeys without a mother figure suffered long-term damage.
  • Later researchers disproved the theory that imprinting cannot be reversed, finding that the animals could exhibit normal sexual behaviour after joining their species.
  • Despite the similarities between humans and apes, the cognitive abilities of humans far exceed those of apes, so the research has generalisability issues.

Animal studies of attachment: Lorenz (1935) & Harlow (1958) Key takeaways

  • Researchers can use animal studies to learn more about human development and behaviour in psychology. This research is called comparative psychology.
  • Animal studies have been used to study attachment. Among the most important studies are those by Konrad Lorenz and Harry Harlow.
  • Lorenz studied geese and found that they imprinted on him because he was the first moving subject the goslings encountered. He suggested that this process was innate and biologically programmed.
  • Harlow's study of rhesus monkeys found that they form emotional attachments to surrogate mothers that provide comfort. He suggested that healthy development and bonding requires more than food.
  • Both researchers suggested that this bonding should occur within a critical period of hatching or birth of the animal. If bonding did not form after this time, the damage from deprivation would be irreversible. This damage has been called maternal deprivation.
  • These studies have greatly inspired attachment research in humans. However, there are ethical and practical concerns due to their nature.

Frequently Asked Questions about Animal Studies of Attachment

Psychologists use animals to research attachment because some animals like mice, rats, and monkeys have brain structures similar to humans. Consequently, the findings can help us understand attachment in humans. There are also fewer ethical concerns about using animals in research.

Harlow studied the attachment of baby rhesus monkeys separated from their biological mother. He tested whether the monkeys could form an attachment to a surrogate mother. He also examined whether the monkeys could suffer from maternal deprivation.

Final Animal Studies of Attachment Quiz


What is one advantage of studying animals in psychology?

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Possible answers: some animals have short gestation periods, some have similar brain structure to humans, less ethical concerns, the likelihood of generalisability.

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What is the name of the practice of studying animals in psychology?

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The practice of studying animals in psychology is called comparative psychology.

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What was Lorenz's leading theory in his study?

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Lorenz's study suggests that young animals have a natural and biological tendency to attach themselves to a single subject.

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Did Lorenz suggest that the effects of imprinting were short-term?

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No. Lorenz suggested that once the animal imprints in infancy, this process is irreversible and has long-term effects on behaviour.

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According to Harlow's study, what is more important for the development of rhesus monkeys?

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Contact comfort is more important to the monkeys as they develop emotional attachments to the surrogate mother.

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What are the critical periods of attachment for both goslings and rhesus monkeys?

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The critical period of attachment for goslings is 12-17 hours after hatching and for rhesus monkeys within 90 days after birth.

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Name one disadvantage of both Lorenz' and Harlow's studies.

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Lorenz' and Harlow's studies lack generalisability due to the differences between animals and humans and are unethical due to the long-term effects on the animals.

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