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The role of nature and nurture in the development of behaviour
Author Paul Kenyon
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This lecture focuses on the work of ethologists who were primarily interested in the evolution of animal behaviour.

bard.gif (15610 bytes)An important aspect of this topic is to alert you to the nature - nurture debate which has political as well as scientific ramifications. It emphasizes once again that science is not pursued in a vacuum; it occurs within a social, political and cultural context.

In The Tempest by William Shakespeare, Pospero refers to Caliban as :
"A devil, a born devil, on whose nature
Nurture can never stick;"

By the end of the topic you should appreciate that behaviour is not simply the result of the unfolding of a genetic blueprint, nor the expression of environmental influences, instead it is a product of the interaction between these two powerful forces.

Learning objectives
After studying the material on this page you should be able to:
  • recognize the names & faces of the founders of ethology and behaviourism
  • list and compare the characteristics of ethology and experimental animal psychology
  • list and explain the four questions asked by ethologists
  • describe the courtship behaviour of male sticklebacks
  • describe the 'nature/nurture' problem
  • explain the significance of Hailman's experiment on development of pecking preference in young herring gulls
  • describe the interaction between innate and environmental factors in the development of bird song
  • understand the role of practice and maturation in the development of behaviour
  • describe preparedness and taste aversion learning
  • Criticize the view that behaviour is either nature or nurture

Founding fathers of ethology and behaviourism

Konrad Lorenz
Niko Tinbergen

In 1972 Lorenz and Tinbergen received the Nobel Prize for their work.

After the second world war there were two broad approaches to the study of animal behaviour in Europe and America.

The European school was founded in the 1930's by the Austrian Konrad Lorenz . He collaborated with the Dutch zoologist Niko Tinbergen to establish 'ethology' which he defined as the 'biological study of behaviour'. Tinbergen's book 'The Study of Instinct' remains the best introduction to the ethological approach to the study of animal behaviour.

The American approach to animal behaviour has its roots in the work of J.B. Watson who in 1924 laid the foundation for an experimental approach to the study of behaviour in his book 'Behaviourism'. Watson was influenced by Pavlov's work on classical conditioning, and the English philosopher John Locke who believed that we are born as a blank slate "tabula rasa" on to which we write the associations we perceive in our environment.

Watson's ideas were adopted by experimental psychologists who were particularly interested in studying learning under laboratory conditions. Perhaps the best known exponent of this approach in its purest form was Fred Skinner who believed that behaviour was shaped by reward. Essentially reward leads to the repetition of a behaviour.

Fred Skinner

The rat's behaviour is 'shaped' by giving a pellet of food delivered via a button in Skinner's hand.

Characteristics of ethology and comparative psychology

Ethologists are concerned with:
  • identifying and describing species-specific behaviours. These are behaviours that show little variability between members of the same species e.g. courtship displays in birds
  • understanding the evolutionary pathway through which the genetic basis for the behaviour came about.
  • Many ethologists capture their observations on videotape or audio tape. From their observations they make an ethogram: a description and documentation of the behavioural patterns under study, a behavioural inventory.
  • The first ethologists were European scientists (e.g. Lorenz, Tinbergen)
    • trained in zoology;
    • studied the evolution of behaviour;
    • in birds, fish and insects;
    • used field experiments and made observations of animal behaviour under natural conditions;
    • discovered species specific fixed action patterns elicited by sign stimuli acting through innate releasing mechanisms;
    • used the term instinct to explain motivation

Behaviourists and comparative psychologists were:
  • initially North American scientists,
  • trained in psychology,
  • rejected the notion of instinct
  • interested in the flexibility of behaviour shown by individuals rather than the evolution of behaviour in species, and
  • understanding the environmental requirements for the development of behaviour in the young;
  • Studied how we learn new behaviours,
  • using a restricted number of species, principally rats and pigeons,
  • under laboratory conditions, using statistical methods and carefully controlled experimental variables,
  • with the intention of discovering general laws of behaviour that could be applied to all species including humans.

Here is a summary of these very different approaches, interests and backgrounds:

Some characteristics of classical ethology and comparative psychology
Feature Classical ethology Comparative psychology
Geographical location Europe North America
Training Zoology Psychology
Typical subjects Birds, fish, insects Mammals, especially lab rats
Emphasis "Instinct", the study of the evolution of behaviour "Learning", the development of general theories of behaviour
Methods Careful observation, field experimentation Laboratory work, control of variables, statistical analysis

Queen Victoria and family

  • Point to ponder:
    What relationship (if any) is there between the scientific approaches adopted by these European and American researchers and the political and cultural systems on the two continents?

President Abraham Lincoln

The four questions ethologists ask about behaviour

Consider the courtship behaviour of the male three-spined stickleback described by Tinbergen (1966). This appears to be innate behaviour: a sequence of fixed action patterns shown by all males in breeding condition, each behaviour triggered by a specific external stimulus . When a ripe female swollen with eggs enters his territory, the male darts towards - and away from - the female in a so-called zigzag dance. The female is led by the male to a nest he has constructed on the floor of the pond or stream. She may creep through the nest and spawn. The male then follows and fertilizes the eggs. He may chase the female away. The male stays by the nest periodically fanning the nest to drive water over it and oxygenate the eggs. Here are several pictures showing this sequence of behaviours.

1. In spring, male sticklebacks come into breeding condition indicated by their bright red bellies and iridescent blue on the back, and build a nest of weed stuck together with sticky kidney fluid. 2. A female- belly swollen with eggs - elicits the male's 'zigzag' dance which terminates in the male sticking his head into the nest entrance. 3. The female enters the nest. 4. The male hovers over the female, prodding the base of her tail which ... 5. .. induces the female to lay her eggs.
6. The male enters the nest and ... 7. .. may drive the female out. She plays no further part in looking after nest, eggs or young. These duties are performed by the male. 8. The male enters the nest, fertilizes the eggs and leaves the nest. 9. The male repairs the nest, mates with two or three other females, and oxygenates the eggs by 'fanning'. 10. The male remains with the nest for about 7 days until the eggs hatch. After hatching, he protects the offspring by picking up strays and spitting them back into the nest.

Ethologists asked four questions about this type of behaviour. How has it evolved and developed? What causes it, and what is its function?

One way of thinking about these questions is to consider them as points on a species' journey through time, from the distant past into the future.

  • The evolution question: How has courtship behaviour evolved in the species? Is it shown by other species of sticklebacks?
  • The development question: How does courtship behaviour develop during the individual's lifetime? Does the male learn the zigzag dance? Does he practice dancing? Is the male successful in directing the female to the nest the first time he dances?
  • The cause question: What causes the male to dance? Are there internal factors that increase the male's tendency to dance? Does increasing daylength in Spring increase the males tendency to dance? Does the swollen belly of a female elicit dancing in males?
  • The function question: Why does the male dance in a particular way? Why does the male prod the female once she has entered the nest? Why does the male fan the eggs? How do these behaviours contribute to the reproductive success of the individual, and ultimately the survival of the species?

Tension between ethology and psychology

It is perhaps not surprising that ethologists and behaviourists would eventually clash over their very different approaches to recording, analysing and interpreting behaviour (e.g. Lehrman. (1953)..

After all they were studying very different types of behaviour.

For example, whilst ethologists were observing courtship displays in the field, psychologists were poring over cumulative records showing the impact of schedules of reinforcement on rates of bar-pressing in rats trained in Skinner boxes under carefully controlled laboratory conditions.

One flash point was interpretation of how behaviour develops.

According to Lorenz, species-specific behaviour develops without the animal experiencing the stimuli to which it responds, or without practice of the motor patterns that it performs. Terms associated with this view that behaviour is the result of 'nature' include:

The American John Watson is credited with emphasizing the role of nurture in development. He wrote

"give me a dozen healthy infants, well -formed, and my own specified world to bring them up in and I'll guarantee to take anyone at random and train them to become any type of specialist I might select - doctor, lawyer, artist, merchant-chief, and, yes, even beggar man and thief , regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors" (see Boakes, 1984, pp226).

Watson was trying to develop a psychology that could be utilized by "the educator, the physician, the jurist and the business man ... in a practical way"

Terms associated with the view that behaviour is the result of 'nurture' include:
  • acquired behaviour
  • learned behaviour
  • environment
We are now going to examine several representative studies that served to break down the notion that development was an either or process; experiments that debunked the notion that behaviour was either the result of nature or purely the result of nurture; experiments that blurred the lines between nature and nurture, and that laid the foundation for the modern view that behaviour develops as an interaction between factors in an animal's environment, as well as biological predispositions.

Nature and nurture in the development of behaviour

Hailman's experiment on development of pecking preference in young herring gulls
Herring gull chicks peck at a red spot on their parents' bill to induce them to regurgitate food. Hailman tested Lorenz's claim that this behaviour is innate.

This diagram indicates that at birth herring gull chicks peck equally often at a model of their own species, and at a model of a laughing gull, but after 6 days of experience receiving food from their parents they show a preference for the model of their own species.

This study shows that the tendency to peck is probably innate, but the object that is pecked is modified as a result of experience

Marler's work on the development of bird song
A sonagram is a visual representation of birdsong

A sonogram is a visual representation of bird song. If your computer has a sound card you can click on this picture of a sonogram to hear the bird song

The development of bird song illustrates how genetic and environmental factors interact during the development of a behaviour. Because bird song in passerines is learnt from others, then song development is an example of culture.

sparrow sonagrams White crowned sparrows have geographically stable dialects.

This diagram shows the similarities in the sonograms of two geographically dispersed subspecies of white crowned sparrow :

  • Nuttal's white crowned sparrow (Zonotrichia leucophyrs nuttalli) which breeds along the central Californian coast
  • Mountain white crown sparrows Zonotrichia leucophyrs oriantha which breed high in the Californian Sierra Nevada mountains
  • For comparison, a sonogram from a swamp sparrow (Melospiza georgiana) a different species of sparrow which lives in Pennsylvania is shown in the diagram.

Within the same species, there are regional variations in bird song. Although these differences could be interpreted as evidence for a genetic basis for bird song, research has shown that young birds learn the dialect from adults in their area.


Development of white crowned sparrow song under normal conditions
From 10 to 50 days of age, the young male's template accepts this adult male white crowned sparrow song as a model:
male white crowned sparrow song
and rejects this swamp swallow song as a model:

swamp swallow song
The improved template now specifies the dialect he has to learn. The young bird does not sing, but the model is remembered for two months or more The maturing male begins singing its sub song at about 150 days of age. During this period vocal output is gradually matched to the dialect specified by the improved template
improved template
At about 200 days of age full song begins, it is a copy of the model he learned in his youth:
full song
Development in isolation from white crowned sparrow song
From 10 to 50 days of age, no acceptable model is provided to the young male so his template remains crude The bird cannot learn a dialect. The young bird does not sing and retains its basic unimproved template for two months or more The maturing male begins sub song (about 150 days). Vocal output develops to match specifications of the unimproved template. No dialect, but some species qualities persist
unimproved template
Full song begins, based on unimproved template (about 200 days)
Full song based on unimproved template
Development after deafening
The young male is deafened before he begins sub song
His template is inaccessible for vocal development
The bird cannot learn a dialect. The young bird does not sing and retains its basic unimproved template for two months or more The maturing male begins sub song (about 150 days). Vocal output cannot be matched to the unimproved template. No dialect, and species qualities are lost
Full song begins, based on unimproved template (about 200 days)
unimproved template

Summary of development of bird song. Marler's experiments clearly show the interaction between innate and environmental factors.

Point to ponder
What are the implications of these results for human development?

Wells' experiments on sepia attack behaviour

Wells' experiments on sepia attack behaviour Here is an experiment which shows that learning can take place by simply practising a response without any reinforcement.

The response of young cuttlefish to a tiny shrimp (Mysis) presented in a glass tube can be divided into the four stages shown in this animation:

  1. a latency before there is any observable response
  2. the nearest eye of the cuttlefish fixates the shrimp
  3. the cuttlefish turns towards the shrimp and both eyes fixate
  4. it attacks and would seize the shrimp if it was not behind a glass wall

Stages 2, 3 and 4 usually take about 10 seconds and this time varies very little with age and experience.

But the duration of stage 1 shows a rapid decline with successive tests as shown in this figure. After 5 trials at the rate of one per day, the latency is reduced from about 120 seconds to 10 seconds or less.

This change is the same whether the attacks are successful or unsuccessful, whether made by a one day old cuttlefish or one starved for 5 days before its first test.

Wells' experiment shows that practice without reinforcement can lead to a change in behaviour. He found that the latency for the cuttlefish to attack a shrimp declined with practice even though the cuttlefish was not reinforced. Note that hunger (increased motivation) did not improve performance of this behaviour.

The only common element appears to be practice in attacking shrimps. Reinforcement does not appear to play a role in the acquisition of this response. 

Point to ponder
What are the implications of these results for human development?

Maturation and practice of pecking by chicks
The development of pecking in newly hatched chicks is an example of the interaction between maturation and practice in the development of a behaviour. Newly hatched chicks have an inherited tendency to peck at objects which contrast with their background, at first their aim is poor but it does improve. Cruze studied how this improvement occurs. He measured pecking accuracy by testing chicks individually in a small arena with a black floor onto which he scattered several grains of millet. Each chick was allowed 25 pecks; each peck was scored as a hit or miss.

Experimental design: Cruze used the following experimental design:

The experiment involved nine independent groups of chicks:
  • Tested after being kept in dark for 24 hours with no opportunity to practice
  • Tested after being kept in dark for 48 hours with no opportunity to practice
  • Kept in dark for 36 hours, given 12 hours in light to practice pecking, then tested when 48 hours old
  • Tested after being kept in dark for 72 hours with no opportunity to practice
  • Kept in dark for 60 hours, given 12 hours in light to practice pecking, then tested when 72 hours old
  • Tested after being kept in dark for 96 hours with no opportunity to practice
  • Kept in dark for 84 hours, given 12 hours in light to practice pecking, then tested when 96 hours old
  • Tested after being kept in dark for 120 hours with no opportunity to practice
  • Kept in dark for 108 hours, given 12 hours in light to practice pecking, then tested when 120 hours old
  • (Chicks were hand fed whilst in the dark)


Conclusion: pecking improves as a consequence of both maturation and practice.

Point to ponder
What are the implications of these results for human development?

Limits to behaviourism: Preparedness and taste aversion learning

Behaviourists such as Skinner gave the impression that it was possible to condition any response that an animal could perform. However, the idea that through the process of operant conditioning, any reinforcer should be equally effective in increasing the frequency of any response was soon in serious doubt.

For example, although it is fairly easy to train a rat to run in a wheel to avoid shock, it proved impossible to condition a rat to rear (stand upright) to avoid the aversive stimulus. Seligman argued that evolution had prepared animals to make certain associations more easily than others. Thus rats are 'prepared' to run, but not to stand on their back legs, to avoid or escape from an unpleasant stimulus (data redrawn from Bolles, 1973)

Garcia and Koelling (1966) carried out a famous experiment on taste aversion learning involving 'bright noisy water' and illness induced by exposure to X-radiation. The training and testing conditions in their experiment are described in this table.

Training conditions Testing conditions Consequences Association learned?
Rats trained to drink water from a spout that caused a flash of light and a click when the rat's tongue touched to spout - 'bright noisy water' Made sick by X-radiation after drinking Offered 'bright noisy water' Drink normally
Given electric shock after drinking Offered 'bright noisy water' Fail to drink
Rats trained to drink water sweetened with saccharine Made sick by X-radiation after drinking Offered water sweetened with saccharine Fail to drink
Given electric shock after drinking Offered water sweetened with saccharine Drink normally

The results show that rats did form an association between

But, rats did not form an association between

According to traditional behaviourists, all the groups of rats should have learned an association between drinking from the spout and the aversive consequences, and should not have drunk under the test conditions. Therefore, Garcia's results challenge the idea that any reinforcer is equally effective in increasing the frequency of any response

Problems with viewing behaviour as either nature or nurture

According to the protagonists, behaviour can be divided into two types
Instinctive (innate, inherited) Learned (acquired)
  • Genes are inherited, but behavioural patterns per se are not inherited
  • Genes do affect behaviour, but all animals develop within some sort of environment (e.g. an animal's mother provides an environment before birth)
  • The 'sameness' of behaviour between members of the same species does not exclude the possibility that all members of a particular species share common learning experiences
  • Deprivation experiments (in which animals are raised in social isolation to remove environmental influences), have been criticized because:
    • the "deprived" environment is still an environment
    • learning can still take place in the deprived environments
  • It is logically impossible to test whether behaviour would develop the same in all environments
  • Learning is a process that changes pre-existing behaviour, therefore we get into a 'chicken and egg' situation. Where does this pre-existing behaviour come from - it cannot be learned!
  • Studies of preparedness and learning predispositions (e.g. taste aversion studies with "bright noisy" water) contradict the idea that through the process of reward and punishment, any stimulus can come to be associated with any response
    • Simple "nature/nurture" or "instinctive/learned" dichotomies have now been abandoned
    • All behaviour depends on both genes and environment
    • Attention is now focussed on experimental investigation of what does, or does not, influence behavioural development
    • Nowadays ethologists and psychologists are less divided by the nature - nurture debate. Both groups are interested in how genetic and environmental factors interact to control the development and expression of behaviour. In turn an individual's behaviour and environment feedback into the organism to determine its future behaviour.


Point to ponder
Can you think of any recent debates about the causes of human behaviour which have been influenced by the nature - nurture debate? Can you classify the participants as taking a 'nature' or 'nurture' or 'interactions' view of human behaviour?


References and online resources

Here is a list of books that extend the topics discussed on this page. You do not need to read all of them. They are included here to give you a choice of further readings.

Supplementary material

HEFCE, the funding body for universities and colleges for the UK, has purchased a 3 year licence to IDEAL, the Academic Press online journal library. If you are a member of a UK academic institution (HEFCE funded) you now have full access rights to this online library which enables you to read the full text of articles in Academic Press journals. 

The following articles cover topics raised in the lecture in greater depth: 

Here is a link to an article by Charles T. Snowdon, past President of the Animal Behavior Society on the Significance of Animal Behavior Research
Abstract from introduction:
"Animal behaviour is the bridge between the molecular and physiological aspects of biology and the ecological. Behavior is the link between organisms and environment and between the nervous system, and the ecosystem. Behavior is one of the most important properties of animal life. Behavior plays a critical role in biological adaptations. Behavior is how we humans define our own lives. Behavior is that part of an organism by which it interacts with its environment. Behavior is as much a part of an organisms as its coat, wings etc. The beauty of an animal includes its behavioural attributes. 

For the same reasons that we study the universe and subatomic particles there is intrinsic interest in the study of animals. In view of the amount of time that television devotes to animal films and the amount of money that people spend on nature books there is much more public interest in animal behaviour than in neutrons and neurons. If human curiosity drives research, then animal behaviour should be near the top of our priorities. 

While the study of animal behaviour is important as a scientific field on its own, our science has made important contributions to other disciplines with applications to the study of human behaviour, to the neurosciences, to the environment and resource management, to the study of animal welfare and to the education of future generations of scientists. "

Copyright Dr. C.A.P. Kenyon 1994-2006