1.3.2 Animal Studies of Attachment: Lorenz and Harlow
Before psychologists could study attachment in human infants under controlled conditions, researchers turned to non-human animals. Animal studies allow greater experimental control and the observation of behaviours across generations — something impractical with human participants. Two studies dominate this topic: Konrad Lorenz's work on imprinting in birds and Harry Harlow's experiments with rhesus monkeys. Together, they reveal fundamental principles about how early bonds form and what happens when they do not. This lesson covers the procedures and findings of both studies (AO1), how to apply them to novel scenarios (AO2), and how to evaluate their strengths and limitations (AO3).
Lorenz's Research — Imprinting
Imprinting
A form of attachment observed in birds and some other animals in which the young attach to and follow the first moving object they encounter shortly after hatching. This occurs within a brief critical period and is difficult to reverse once established.
Konrad Lorenz was an Austrian ethologist — a researcher who studies animal behaviour in natural settings. His most famous contribution to attachment research was demonstrating the phenomenon of imprinting through a carefully designed study with geese.
Lorenz (1952) — Lorenz divided a large clutch of goose eggs into two groups. One half was left to hatch naturally with the mother goose present. The other half was placed in an incubator so that the first moving object the goslings saw after hatching was Lorenz himself. The incubator-hatched goslings followed Lorenz everywhere, treating him as their mother figure, while the naturally hatched goslings followed the mother goose. When the two groups were mixed together, the goslings did not switch — each group continued to follow whichever figure they had first encountered. This was a natural experiment with field observation, as Lorenz manipulated the hatching conditions but observed the resulting behaviour in a relatively natural setting.
Lorenz identified a critical period for imprinting — a narrow window shortly after hatching (varying by species but often just a few hours) during which the young bird must encounter a moving object in order to imprint. If no moving object is present during this window, imprinting fails to occur and cannot be established later.
Sexual imprinting
Lorenz also observed that imprinting influenced later mate preferences — a phenomenon he called sexual imprinting. Birds that imprinted on a non-bird figure would later direct courtship behaviour towards that type of figure rather than towards members of their own species. In one case study, Lorenz (1952) described a peacock that had been reared in the reptile house of a zoo, where the first moving objects it saw were giant tortoises. As an adult, the peacock directed courtship behaviour exclusively towards giant tortoises rather than peahens, suggesting that imprinting had shaped its sexual preferences.
Lorenz demonstrated that attachment in birds is not learned gradually — it occurs rapidly through imprinting during a critical period shortly after hatching, and it shapes both social and sexual behaviour in later life.
Harlow's Research — Contact Comfort
Contact comfort
The physical comfort and reassurance provided by close bodily contact with a soft attachment figure. Harlow demonstrated that infant monkeys preferred contact comfort over food when forming attachments.
While Lorenz studied birds, the American psychologist Harry Harlow investigated attachment in rhesus monkeys — a species far closer to humans in terms of brain structure, social behaviour, and the complexity of the mother-infant bond. Harlow's research challenged the dominant theory of his time: the learning theory (or 'cupboard love' theory) of attachment, which proposed that infants become attached to their caregivers because caregivers provide food. If this were true, an infant should attach to whichever figure feeds it.
Harlow (1958) — Harlow reared 16 baby rhesus monkeys with two artificial surrogate 'mothers' made of wire. One surrogate was wrapped in soft cloth; the other was left as bare wire. In one condition, the plain-wire mother dispensed milk; in the other condition, the cloth-covered mother dispensed milk. Harlow then observed which surrogate the infant monkeys spent time with, and which they ran to when frightened (e.g. by a noisy mechanical teddy bear). This was a laboratory experiment, as the independent variable (which surrogate dispensed milk) was deliberately manipulated under controlled conditions.
The results were striking. Regardless of which surrogate dispensed milk, the baby monkeys overwhelmingly preferred the cloth-covered mother. They spent the majority of their time clinging to the soft surrogate and, when frightened, always ran to the cloth-covered mother for comfort — even if their milk came from the wire mother. Harlow concluded that contact comfort was far more important than food in the formation of attachment. This directly contradicted the learning theory of attachment, which predicted that the monkeys should attach to whichever figure provided nourishment.
Priya is a nursery worker who notices that a new baby, Leo, has been left with a soft blanket by his mother on his first day. Whenever Leo becomes distressed or startled by a loud noise, he clutches the blanket tightly and holds it against his face rather than reaching for the bottle of milk nearby. Priya observes that Leo seems calmer and more settled when holding the blanket than when being fed. This behaviour illustrates Harlow's finding that contact comfort — the reassurance provided by something soft — is more important to infants than food provision when seeking security.
Long-Term Effects of Maternal Deprivation
Harlow and his colleagues followed the maternally deprived monkeys into adulthood to investigate whether early deprivation had lasting consequences. The findings revealed severe and permanent effects on social development. Monkeys raised with only the wire mother showed the most extreme dysfunction, but even those reared with the cloth-covered surrogate did not develop normally. These monkeys were more aggressive and considerably less sociable than monkeys raised with a real mother. They were unskilled at mating and bred less frequently. Most disturbingly, when the deprived female monkeys eventually became mothers themselves, some neglected their offspring entirely, while others physically attacked or even killed their young.
Harlow concluded that there was a critical period for normal attachment development in rhesus monkeys. A mother figure had to be introduced within approximately 90 days of birth for a normal attachment to form. After this point, the damage caused by early deprivation appeared to be irreversible.
| Finding | Cloth-covered mother | Wire mother | Real mother baseline |
|---|---|---|---|
| Time spent with surrogate | Infant monkeys spent most of their time clinging to the cloth surrogate | Infant monkeys spent relatively little time with the wire surrogate, except briefly for feeding | Normal attachment behaviour would centre on a real caregiver |
| Response when frightened | Monkeys ran to the cloth mother for comfort | Offered little comfort when the monkeys were frightened | A real mother would normally provide comfort and security |
| Effect of milk provision | Preferred even when it did not provide milk | Not preferred even when it did provide milk | A real mother provides both nourishment and comfort |
| Long-term outcomes | Some later social problems still occurred, despite the comfort provided | Showed the most severe social and emotional dysfunction | Monkeys raised by real mothers developed more normally socially and emotionally |
These findings carry significant implications for our understanding of human attachment. Although we must be cautious about generalising directly from monkeys to humans, Harlow's work strongly suggests that the quality of early caregiving — not simply the provision of physical needs like food — is critical for healthy emotional and social development.
Evaluation of Lorenz's and Harlow's Research
Both Lorenz's and Harlow's studies have shaped our understanding of attachment, but each has significant strengths and limitations that AQA examiners expect you to discuss. When evaluating animal studies, two recurring issues are generalisability to humans and ethical concerns. However, strong evaluation goes beyond simply naming these issues — you must explain precisely why they matter for each study.
Limitations of generalising Lorenz to humans
The mammalian attachment system is fundamentally different from that of birds. In birds, imprinting is a one-way process — the young bird follows the parent figure, but the parent does not necessarily form a reciprocal emotional bond. In mammals (including humans), attachment is a two-way process: both the infant and the caregiver develop emotional bonds with each other. Human attachment also develops more gradually and is shaped by the quality of ongoing interaction, not simply by the first moving object encountered. This means that Lorenz's concept of imprinting cannot be straightforwardly applied to human attachment.
Is imprinting permanent?
Lorenz claimed that imprinting was irreversible once established. However, Guiton (1966) challenged this by demonstrating that chickens that had imprinted on yellow rubber gloves (and initially directed courtship behaviour towards the gloves) eventually learned to prefer mating with other chickens. This suggests that imprinting may not be as permanent as Lorenz believed, and that later experience and learning can override early imprinting — at least in some cases.
Practical applications of Harlow's research
Despite its ethical controversies, Harlow's research has had substantial real-world impact. His findings have informed the care of animals in zoos and breeding programmes by demonstrating that animals need attachment figures and contact comfort for healthy development — not just food and shelter. The research has also influenced social work and clinical psychology, helping professionals understand that a lack of early bonding is a significant risk factor in child development (Howe, 1998), enabling earlier intervention for children raised in conditions of neglect or deprivation.
Evaluation Bank (AO3)
Strength: Harlow's research has significant practical value because its findings have been directly applied to improve animal welfare and child protection. His demonstration that contact comfort and early bonding — not merely food provision — are essential for healthy development has informed the design of zoo environments and breeding programmes, where animals are now provided with attachment figures and soft materials. More importantly, the research has influenced social work practice by helping professionals recognise that a lack of early bonding experience is a major risk factor for developmental problems (Howe, 1998), allowing earlier intervention for children in neglectful environments. This means Harlow's research has value beyond theoretical understanding — it has tangible benefits for both animal welfare and human child protection. This relates to the broader debate about whether the ethical costs of animal research can be justified by its practical contributions to knowledge and welfare.
Limitation: A significant limitation of both Lorenz's and Harlow's research is the difficulty of generalising findings from non-human animals to humans. Lorenz studied birds, in which imprinting is a rapid, one-directional process occurring within hours of hatching, whereas human attachment is a two-way emotional bond that develops gradually over months through ongoing caregiver-infant interaction. Harlow's research used rhesus monkeys, which are biologically closer to humans than birds, but human attachment is still more complex — shaped by language, cognition, and cultural practices that have no equivalent in monkey behaviour. This means that while both studies offer valuable insights into basic attachment mechanisms, their findings cannot be directly applied to explain the full complexity of human attachment. This connects to the nature-nurture debate: Lorenz and Harlow emphasised innate, biologically driven attachment processes (nature), but human attachment is also heavily influenced by the quality of caregiving, social context, and individual experience (nurture), suggesting a more interactionist explanation is needed.
Limitation: Harlow's research raises serious ethical concerns that cannot be dismissed, even though the findings proved valuable. The infant monkeys experienced prolonged maternal deprivation that caused severe and lasting psychological harm — including social withdrawal, aggression, inability to mate, and abusive behaviour towards their own offspring. Harlow was aware that these outcomes were likely, yet proceeded with the research. While the study could not have been conducted ethically on human participants (making animal research the only viable option for studying deprivation experimentally), the degree of suffering inflicted raises questions about whether the scientific benefits justified the cost. A cost-benefit analysis would weigh the substantial contributions to attachment theory and child welfare practice against the permanent damage caused to the animals involved. This connects to the wider ethical debate in psychology about the use of animals in research — specifically, whether it is morally acceptable to cause suffering to non-human animals in order to advance knowledge that benefits humans.