Konrad Lorenz (1903–1989) was an Austrian zoologist who discovered imprinting. Imprinting is the process by which young animals form a lasting attachment to the first moving object they see after birth.
His experiments with geese and ducks showed that this attachment forms automatically. It happens within a brief critical period, a short window early in life. Feeding plays no part.
The finding suggested that early social bonds can be innate, and it later shaped psychologist John Bowlby’s theory of human attachment.
Key Takeaways
- Imprinting: Goslings and ducklings form an attachment to the first large moving object they see after hatching, without needing to be fed.
- Critical Period: Hess (1958) found imprinting was strongest between 12 and 17 hours after hatching and rare after 32 hours.
- Reversibility: Guiton (1966) found that later contact with an animal’s own species can partly reverse an imprint. Sluckin (1965) proposed a flexible sensitive period instead.
- Attachment Theory: Lorenz’s non-feeding evidence helped psychologist John Bowlby argue that human attachment is innate rather than based on feeding.
- Nobel Prize: Lorenz shared the 1973 Nobel Prize in Physiology or Medicine with Tinbergen and von Frisch for founding ethology.
Imprinting suggests that attachment is innate and programmed genetically.
Psychologist John Bowlby later drew directly on this finding. Lorenz’s goslings formed their attachment without any feeding taking place.
This challenged learning-theory accounts of the mother-infant bond, sometimes called ‘cupboard love’ theory, which held that infants attach to whoever feeds them. Bowlby (1969) argued instead that attachment evolves as an innate behavioural system.
Julian Huxley introduced Bowlby to Lorenz’s ethological writings in 1951, as Bowlby recorded in the preface to Attachment (Bowlby, 1969). In Bowlby’s account, species-typical triggers keep a caregiver close. They include crying, smiling, and clinging.
Lorenz’s Imprinting Experiment With Geese
Lorenz’s 1935 Goose Experiment
Lorenz’s best-known demonstration separated newly hatched goslings from their mother and tested whom they would follow.
- Aim: To find out how young birds come to recognise and follow their own species, and whether feeding or an inherited template explains it.
- Method: Half a clutch of greylag goose eggs hatched under a goose, while Lorenz incubated the rest and was the first moving object they saw. He then mixed both groups under an upturned box.
- Results: Goslings hatched with Lorenz followed him, while the other group followed the goose; when the box was lifted, each group went to its own ‘mother’. The preference formed within hours of hatching.
- Conclusion: A lasting preference forms during a brief critical period through exposure alone, with no feeding or reward. Lorenz argued the trigger is broad enough to accept a human, and that the bond, once formed, is stable (Lorenz, 1935).
This following response is what Lorenz called imprinting. Lorenz-imprinted birds continued as adults to direct social, and sometimes sexual, behaviour toward humans.
Lorenz believed that once imprinting has occurred, it cannot be reversed, nor can a gosling imprint on anything else. Later research challenged the claim of irreversibility.
Guiton’s Rubber Glove Study (1966)
Guiton tested what happens when chicks imprint on something that is not a bird at all.
- Aim: To test whether imprinting is permanent, and what happens to an imprint on an unnatural object when the bird later meets its own species.
- Method: Brown leghorn chicks were reared in isolation, with a yellow rubber glove used to feed and handle them during the critical period. Some were later housed with other chickens for an extended period and retested.
- Results: The chicks imprinted on the glove, and glove-reared cockerels later tried to mate with it. Birds later housed with hens gradually shifted their courtship toward them and lost their preference for the glove.
- Conclusion: Imprinting can occur on objects far outside the species’ natural range, but it is not permanent. Later experience with its own species can override an early imprint (Guiton, 1966).
The result corroborated Lorenz’s original findings. A preference formed in early life persisted into adulthood. Guiton (1966) called this lasting change in social and sexual behaviour sexual imprinting, an early attachment that shapes adult mating preferences.
The Critical Period: Hess’s Duckling Study
Imprinting does not appear to be active immediately after hatching, although there seems to be a critical period during which imprinting can occur. Eckhard Hess measured that window in mallard ducklings.
- Aim: To measure how imprintability changes with age in mallard ducklings, and to define the critical period more precisely than Lorenz’s qualitative account.
- Method: Mallard ducklings, hatched in the dark, saw a moving decoy briefly at ages from one hour to three days. Each was later tested on a choice between that decoy and a new one.
- Results: Imprinting strength rose from near zero at hatching, peaked at about 12 to 17 hours, and was unlikely after about 32 hours. Ducklings that worked harder to follow the model formed stronger preferences.
- Conclusion: In mallards, imprintability follows an onset, peak and offset profile over roughly the first day and a half. The same exposure afterwards has little lasting effect (Hess, 1958, 1959).
Like Lorenz, Hess believed the preference was permanent.
Imprinting has consequences, both for short-term survival, and in the longer term forming internal templates for later relationships. Imprinting occurs without any feeding taking place.
However, Lorenz’s claim that imprinting produces a permanent, irreversible change in the nervous system has since been criticised.
Guiton (1966) found that after chicks spent time with their own species, they could still engage in normal sexual behaviour, suggesting imprinting is only moderately reversible. Klein, Hoffman, and DePaulo (1976) reported a similar reversal in ducklings.
Critical Evaluation
The imprinting phenomenon itself has been replicated many times since Lorenz’s original demonstration. Parts of his wider theoretical framework have not survived as well.
Three criticisms stand out, each covered below:
- Critical Period: Lorenz’s rigid window and permanent imprint gave way to the flexible sensitive period.
- Hydraulic Model: Ethologists rejected his energy build-up theory of instinct and its extension to human aggression.
- Human Attachment: Whether imprinting transfers from birds to human infants remains contested.
From Critical Period to Sensitive Period
Lorenz originally described a strict critical period. Outside this narrow window, he believed imprinting could not occur at all, and a formed preference could never be reversed.
Guiton’s (1966) glove-reared chicks challenged that picture directly. Wladyslaw Sluckin (1965) then reviewed a decade of imprinting research in his book Imprinting and Early Learning.
Sluckin proposed a new idea: the sensitive period.
This is a stage when the relevant learning is most likely and easiest, but not strictly switched on or off. Under this model, learning can still occur outside the sensitive window, only slower and less complete.
The two models differ on three points:
| Feature | Lorenz: critical period | Sluckin: sensitive period |
|---|---|---|
| Timing | A strict, all-or-none window | A stage when learning is most likely and easiest |
| Outside the window | Imprinting cannot occur | Learning can still occur, more slowly and less completely |
| Permanence | A formed preference can never be reversed | Reversible under some conditions, as Guiton’s chicks showed |
This softer framework fit the evidence on reversibility and on unusual imprinting ages far better than Lorenz’s original version.
This concept is now standard. It spans vision, hearing, birdsong, and language research, and John Bowlby adopted the same term for the human attachment window.
Bateson later explained why the window closes (Bateson, 1979). In his account, imprinting is self-terminating: the act of imprinting on a preferred object itself suppresses further plasticity. The window closes because imprinting has done its work, not because an internal clock runs out.
The Hydraulic Model of Motivation
Lorenz also proposed that instinctive behaviour was driven by a build-up of action-specific energy. On this model, energy accumulated within the animal and discharged once the right stimulus appeared, much like water held back by a valve.
The model was already disputed during Lorenz’s own lifetime. Robert Hinde (1960, 1970) showed that the physiological evidence did not support a literal energy build-up.
Mainstream ethology has since dropped the idea.
The hydraulic picture is no longer treated as an adequate account of motivation. The same energy model underpinned Lorenz’s popular book On Aggression (1966), which argued that human violence builds up inside us and needs periodic release.
Scientific reviewers rejected the human generalisation. S. A. Barnett (1967) called it unsupported by evidence, and Erich Fromm (1973) mounted a book-length critique from a broader biosocial standpoint.
Fromm argued that Lorenz drew mostly on fish, birds, and a few non-primate mammals. That base was too narrow, he said, to explain the specifically human destructiveness he called malignant, which has no close animal parallel.
Does Imprinting Explain Human Attachment?
The imprinting evidence is strongest in birds. Extending it to human infants is a bigger step.
Bowlby’s adoption of imprinting settled less than textbook summaries suggest. A 2022 theoretical review by Robledo and colleagues revisited the imprinting literature to test how far it supports his theory (Robledo et al., 2022).
They argued that the critical period, the irreversibility of the imprint, and the wider criteria for imprinting are less clear-cut once research moves beyond birds.
The analogy is weaker than it looks.
Human infants can neither follow like a gosling nor cling like an infant primate. The authors argue that infants rely instead on a communicative route to closeness: crying, smiling, and vocalising. Lorenz’s model was never built to describe that route.
On this reading, imprinting and attachment are complementary accounts of related but distinct phenomena. They are not the direct transplant from geese to infants that textbook shorthand often implies.
Contemporary Research
Modern research has moved from behaviour to the brain. Brian McCabe’s review of the field (McCabe, 2019) describes how visual imprinting in young chicks is now understood as a well-defined form of learning.
It centres on one forebrain region, the intermediate medial mesopallium (IMM). The review links the IMM to imprinting in three ways:
- Structure: After exposure to an imprinting stimulus, the postsynaptic density, the receiving side of each synapse, grows longer.
- Chemistry: NMDA receptors change in composition, and specific immediate-early genes, which switch on quickly after neural activity, become active.
- Lesions: Removing the IMM abolishes the acquired preference, while unlearned predispositions and other kinds of learning stay intact.
Johan Bolhuis and Robert Honey (1998) had earlier brought the behavioural and neurobiological evidence together to make the same case. Together, this research confirms that the imprinting effect Lorenz described in 1935 is real and repeatable.
It replaces his hydraulic-energy explanation with a detailed account grounded in identified brain circuits.
McCabe’s review also describes computational models. They range from simple Hebbian networks, in which connections strengthen through shared activity, to deep-learning systems. These models reproduce the core pattern of imprinting from broad perceptual predispositions plus experience-dependent tuning. None needs a rigid, all-or-none critical period.
Who Was Konrad Lorenz?
Konrad Zacharias Lorenz was born in Vienna on 7 November 1903, the son of surgeon Adolf Lorenz. He grew up at the family’s estate in Altenberg, on the Danube, where he kept and observed animals from childhood.
Early Life and the Founding of Ethology
Lorenz’s father steered him toward medicine. He studied briefly at Columbia University in New York in 1922, then returned to Vienna and qualified in medicine from the University of Vienna in 1928.
He also read for a doctorate in zoology, submitting a thesis on the comparative behaviour of crows and their relatives, and was awarded his PhD in 1933.
Between 1927 and 1937, working largely without institutional support, Lorenz carried out his classic fieldwork on jackdaws, geese, and ducks at Altenberg. He published prolifically in the Journal für Ornithologie.
In 1936 he met fellow zoologist Nikolaas Tinbergen, and hosted him at Altenberg the following year. Together they laid the foundations of ethology, the biological study of animal behaviour under natural conditions.
Core Ideas of Classical Ethology
Lorenz’s lasting contribution to ethology was its conceptual toolkit. In a 1937 paper he set out the building blocks of instinctive behaviour (Lorenz, 1937).
- Fixed Action Pattern: A stereotyped, species-typical movement sequence that, once triggered, runs to completion largely regardless of feedback.
- Sign Stimulus: The specific feature of the environment that triggers a fixed action pattern.
- Innate Releasing Mechanism: The animal’s internal perceptual filter, which recognises the sign stimulus and lets the movement run.
- Hydraulic Model: Lorenz’s picture of energy building up inside the animal and releasing when a sign stimulus opens a valve.
The first three concepts remain in use. Researchers often prefer the term modal action pattern, because ‘fixed’ understates how much real behaviour varies (Barlow, 1977). The hydraulic model did not survive. The Critical Evaluation section explains why.
Nikolaas Tinbergen supplied the experimental discipline, using controlled field studies with dummy stimuli. With Lorenz he studied the greylag goose’s egg-rolling response, which became the textbook example of a fixed action pattern (Lorenz & Tinbergen, 1938).
A mother goose retrieves a displaced egg with a side-to-side movement of her bill. The movement runs to completion. It continues even if the egg is removed partway through.
Tinbergen (1963) later framed ethology around four questions: causation, development, function, and evolutionary history.
The Nazi Period
In 1938, after Austria’s annexation, Lorenz joined the Nazi Party. In 1940 he took up a chair at the University of Königsberg with the party’s backing.
The chair once belonged to Immanuel Kant.
A 1940 paper, Durch Domestikation verursachte Störungen arteigenen Verhaltens (“Disturbances of species-specific behaviour caused by domestication”), applied his ideas about animal ‘degeneration’ to human society.
It argued that civilisation had weakened humans’ species-typical behaviour and that a programme of racial hygiene was therefore biologically justified (Lorenz, 1940). Historians treat this as a genuine and troubling part of his record (Deichmann, 1996; Sax, 1997).
He served as a German army psychiatrist during the war. He then spent nearly four years as a prisoner of war in the Soviet Union.
After the war, Lorenz called his party membership a serious error of judgement, though historians note he never fully retracted the 1940 paper’s arguments.
The University of Salzburg revoked an honorary doctorate it had given him, citing this history, in 2015.
Historians hold two judgements together. Lorenz actively lent his scientific authority to the Nazi project, unlike scientists whose party membership was nominal (Deichmann, 1996; Sax, 1997).
Yet his best ethology has held up independently of the uses he put it to in 1940–43. That includes his goose observations and the description of imprinting.
Later Career and the Nobel Prize
Lorenz returned to a defeated Austria in 1948. No academic post was open to a man with his political record, so he worked for a time from Altenberg on a small grant.
Help arrived in 1950.
The Max Planck Society, through the efforts of Erich von Holst, established a research station for him at Buldern in Westphalia. It was reconstituted in 1961 as the Max Planck Institute for Behavioural Physiology at Seewiesen, in Bavaria, with Lorenz as founding co-director.
The Seewiesen years were the summit of his career.
In 1973 he shared the Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch for establishing ethology as a science. Lorenz retired from Seewiesen that same year and returned to Altenberg.
Altenberg welcomed him back.
The Austrian Academy of Sciences opened a department for animal sociology to house his work. He continued studying his greylag geese at the Konrad-Lorenz-Forschungsstelle in Grünau im Almtal, which he founded in 1973.
He died at Altenberg on 27 February 1989, aged 85.
References
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