This lecture introduces you to some of the very elegant experimental methodologies developed by ethologists. Hopefully you will begin to appreciate that an animal's view the world in a very different way from ours - the dog lives in a 'smelly world', the owl lives in a nocturnal world of rustlings etc. - and how ethological techniques can be used to understand these worlds.
The lecture introduces the idea that behaviour as well as structure evolves.
The heart of the lecture is a discussion of how ethologists have used models to understand the significance of stimuli in an animal's world. You should avoid thinking of these techniques as only being applicable to the analysis of animal behaviour. You may find them useful in unravelling the complexities of human behaviour as well.
An ethological model of motivation is used to knit together some of the concepts introduced in the lecture. This model has some disturbing things to say about the inevitability of human aggression. By now you should be able to judge for yourselves the validity of the claims made by the model.
Studying the material on this page should enable you to:
But it gets even more mysterious, we are probably not even aware of the sensory systems that control our own behaviour! Consider the case of human pheromones.
In 1971 McClintock reported that groups of women living together were more likely to have synchronized menstrual cycles than was expected by chance. Studies on women in university hostels show that within four months of living together their menstrual cycles tend to start at around the same time each month. And when women move in with men, their menstrual-cycle length shortens, so that they are fertile more often. McClintock & Stern tested if these effects involved pheromones. "The researchers collected body odour on cotton pads from women, and wiped them on the upper lips of recipient women. This was repeated daily over the next two menstrual cycles. The researchers found that the timing of the cycle was indeed altered in a systematic way. Odour from the follicular phase of the menstrual cycle accelerated the surge of luteinizing hormone, which precedes ovulation, and so shortened the menstrual cycle. Compounds from the same donors obtained later in the menstrual cycle, at ovulation, delayed the hormone surge and so lengthened the cycle."
You can read more about this fascinating research in this article in Nature (12 March 1998) : Lifelines: Communicating by body odours by Helen Phillips.
Point to ponder
How would you investigate the effect(s) of female pheromones on human male behaviour?
What is the evolutionary advantage of pheromones?
The digger wasp , Philanthus triangulum, builds a nest burrow in sand that contains developing larvae which she supplies with food. How does the wasp find her way back to the nest after returning from a hunting trip? Tinbergen concluded that she used visual cues around the nest on the basis of the following experiment:
Whilst she was in the burrow Tinbergen placed a circle of pine cones around the entrance. When she emerged, the wasp reacted to the new situation by a wavering orientation flight (training conditions) before flying off. Returning with prey (testing condition), she flew to the circle of pine cones even though it had been moved during her absence.
The animation shows the wasp's flight behaviour during training and test conditions. You may need to watch it repeat a few times to understand what is going on.
Lorenz considered that every species has a repertoire of stereotyped behaviours called Fixed Action Patterns. Lorenz considered that they were
innate and used the German word 'Erbkoordination' which translates literally as 'inherited co-ordination' to describe them. common to all members of the species (species-typical) and therefore they are as characteristic of the species as shared structural features once triggered by sign stimuli, fixed action patterns proceeded in the absence of the triggering stimulus. Lorenz noticed that egg retrieval by greylag geese proceeded even if he removed the egg after the behaviour had been triggered by an egg lying outside the nest. Here is a videoof this behaviour.
The next section shows stereotyped courtship patterns in birds. We have already examined the courtship behaviour of sticklebacks, which is another example of a Fixed Action Pattern.
Fixed action patterns can be used to follow the evolution of behaviour because they vary between related species of animals. This analysis was one of the main interests of early ethologists.
Do humans exhibit Fixed Action Patterns? This question was addressed by Irenaeus Eibl-Eibesfeldtand Hans Hass who worked at the Max-Planck-Institute for Behavioural Physiology in Germany. They created a Film Archive of Human Ethologyof unstaged and minimally disturbed social behaviour.
They filmed people across a wide range of cultures with a right-angle reflex lens camera i.e. the subjects did not realize that they were being filmed because the camera lens did not appear to be pointing at them! Eibl-Eibesfeldt has identified and recorded on film, several human Fixed Action Patterns or human 'universals' e.g. smiling and the "eyebrow-flash"
Eibl-Eibesfeldt took these pictures of a Himba woman from Namibia (SW-Africa). She shows a rapid brow raising (between the second and third still images) which coincides with raising her eyelids. Because all the cultures he examined showed this behaviour, Eibl-Eibesfeldt concluded that it was a human 'universal' or Fixed Action Pattern.
Further examples of Eibl-Eibesfeldt's filmsof human FAPs / 'universals' include:
coyness behavior in different cultures emotions in a deaf blind child a cross-cultural overview on the occurrence of the eye-brow-flash.
Nowadays the term Fixed Action Pattern has been dropped from ethology and substituted by the phrases 'behaviour patterns' or 'behavioural acts' because:
Behaviour is not as fixed as implied by the term Fixed Action Pattern. There are subtle variations between and within animals in, for example, the duration of individual components they vary around a mean value Fixed Action Patterns are not simply innate. They can be subtly modified by experience. Behaviour is modified as a result of the animal's environment - it is not always triggered in the presence of the external stimulus.
Apparently it is difficult to train a sheepdog to drive sheep away from a human, and to leave one group of sheep to go and gather more. You can see these behaviours tested in the fetch and outrun sections of a sheepdog trial.
In a previous lecturewe have explored the courtship behaviour of the male three-spined stickleback.
In Spring male sticklebacks change colour, establish a territory and build a nest. They attack male sticklebacks that enter their territory, but court females and entice them to enter the nest to lay eggs.
Tinbergen (1951) used crude models of sticklebacks to investigate which features of male and female sticklebacks elicited attack and courtship behaviour from male sticklebacks.
This diagram shows Tinbergen's main findings:
by male sticklebacks.
The term sign stimulus or releaser was used to describe simple features (e.g. red belly) of a complex stimulus (e.g. male stickleback) that bring about a particular fixed action pattern (e.g. head down attack behaviour in male sticklebacks).
He discovered that the birds would gape at a protuberance (head) on the side of a body model.
You might think that the birds would gape at the bigger head, but in fact
Tinbergen found that the relative size of the head was more important than
its absolute size. Presumably the birds preferred the 'head' that was the
proper size for the model's 'body'.
Some of the most colourful examples are the bright coloured plumage of male birds that help them attract mates.
In addition male birds often have behavioural displays that enhance their attractiveness to females. In contrast many female birds are relatively dowdy.
You will recall from the first lecture in this seriesthat ethologists asked four questions about behaviour. How has it evolved and developed? What causes it, and what is its function? We are now going to focus on the first of these: How does behaviour evolve?
Ethologists have used the comparative method to attempt to reconstruct the history of a species. This involves comparing the behaviour of related species that exist today in order to understand their evolution.
This diagram shows the behaviour of four imaginary species (A,B,C and D) that are alive today. All four species share a common ancestor that lived millions of years ago which is represented by the red symbol on the diagram. The contemporary species exhibit behaviour that can be attributed to this common ancestor. Notice how the blue ancestor only contributes to the behaviour of three contemporary species (B,C & D) and so on.
This diagram makes the important point that the species we see in the world today have not evolved from each other. Thus species A is in one sense more primitive than species D, but species D has not evolved from species A. Instead we say that they share a common ancestor from millions of years ago. Thus the idea that humans have evolved from apes is a myth. Humans and apes share a common ancestor. This is one reason why it is interesting to study the behaviour of apes. This type of research may highlight similarities in the behaviour of the two species that can be attributed to our common evolutionary history - up to a point. The diagram also shows that each species is not simply the accumulation of ancestral behaviours. The foreground colour for each species is unique and different for each species. Thus contemporary species are much more than simply 'the sum of the parts of its ancestors'. Each contemporary species is unique, and the result of selection pressures during its evolution, and the evolution of its ancestors.
Point to ponder: The next section contains details of the plumage and bowers built by a number of species of bower birds that live in Australia and New Guinea.
This is a very simplified diagram, it is possible for the same behaviour to evolve in species that do not share a common ancestor with the particular feature.
Features that are similar because they have evolved from a common ancestor are said to be homologous. For example, the wings of birds, human arms, and pectoral fin in fish are all derived from a common ancestor In contrast, features that are similar because they have evolved in response to a common environmental pressure are said to be analogous. For example, birds and insect wings have evolved to support flight, not because birds and insects share a common ancestor with this feature.
Bower birds are a family of birds in which males attract mates by collecting brightly coloured objects which they display to females in 'avenues' or on 'maypoles'. There is an interesting relationship between the colourfulness of a male's plumage, the visual properties of the objects they collect, and the complexity of the structures they build to house these objects. Female bower birds are rather drab creatures. Some species of male bower bird are also relatively drab, but they make up for this by building elaborate structures decorated by brightly coloured objects.
Supernormal stimuli is the phrase used to describe artificial stimuli that are more effective than the real thing in eliciting a behavioural response.
Herring gull chicks peck at a red spot on their parents's bill to induce their parents to regurgitate food. Chicks will also peck at a model consisting of a red spot against a yellow packground.
However it is possible to construct a model that is even more effective than a real head by using a red pencil with three white bars at the end. This is an example of a supernormal stimulus.
I wonder why animals respond to supernormal stimuli more vigorously than to a more realistic model. You might expect herring gulls to have evolved so that they more closely match the characteristics of the supernormal stimulus. But a long narrow bill might have compromised their ability to feed. So clearly there is a balance to be struck here between the feeding demands of the adult and young birds.
But the existence of supernormal stimuli shows that there is room for evolution to proceed. If this were not the case evolution would only occur in the face of changing environmental conditions.
Are we sensitive to supernormal stimuli? There is no clear cut evidence on this point but humans do seem to spend an extraordinary amount of time improving on their basic physical attractiveness. But because these devices show such cultural variation it is difficult to say they represent supernormal stimuli that work for every member of our species i.e. they do not have the universal appeal we would expect from a sign stimulus.
Some of these babylike features can be seen in these pictures of two members of the all-girl pop group 'The Spice Girls', one member is known as 'Baby Spice'
In an elegant series of experiments, Baerends & Kruijt investigated what properties of the egg signalled to the gull that it should be retrieved back into the nest. They removed two eggs from the nest and placed two dummies on the nest rim. The dummies were of various sizes, shapes and colours.
The investigators were interested in exploring the birds' retrieval preferences:
It proved impossible to carry out a simple preference test because when two identical sized dummies were placed on the nest rim, the gull usually revealed a marked position preference, retrieving the dummy on the left first (or vice versa).
To overcome this problem, Baerends & Kruijt employed a very elegant titration technique in which position was titrated againt size. In anthropomorphic terms they said to the gull
"OK, we know you prefer the egg on your left / right hand side, but if we put this bigger egg on the right / left hand side will you retrieve it first?"
This diagram shows the titration method of determining the value of an egg dummy.
The large brown circle represents the nest with one egg in the nest bowl and two dummies on the rim.
The numbers 7,8,9,10,11,12 refer to the size of the dummies, r is the ratio of the sizes of the dummies on the nest rim. The dummy chosen on each trial is indicated in black.
X is the model to be measured.
Row 1: Determination of the value of the gull's position preference. Starting from the left hand sise, the first test with two size 8 eggs, shows that the right-hand egg is preferred. This shows that the bird has a preference for eggs on the right hand side. The next test (to the right) shows that this preference remains when a smaller egg (size 7) is substituted on the right hand side. The sequence of tests shows that the value of the position preference lies between r=1.3 and r=1.5.
Row 2: Determination of the value of model X. The control tests show that the position preference remains unchanged- the bird continues to show a right hand side position preference. The experimental tests show that the value of X lies between egg sizes 8 and 10. (After Baerends and Kruijt, 1973)
Point to ponder
Can you think of any other experimental investigation that could utilise the 'titration method'?
Several types of dummy eggs were used:
The picture shows the influence of egg size and colour on retrieval
The numbers 4 to 16 indicate the relative sizes of the dummy eggs used
Results of the titration tests.
Baerends & Kruijt found that herring gulls:
Note that the gulls prefer a green background colour to the normal speckled
brown colour of gull eggs.
For example, a size 5 green egg is more attractive than a size 6 natural coloured egg. Because they also prefer eggs with speckles, this leads to the surprising observation that a size 5 green speckled egg is more attractive than a size 8 natural coloured egg.
The important finding is that the preference for larger eggs remains the same when other features like shape and colour are changed. This means that each feature (colour and speckling) adds a specific contribution that is independent of the contribution of the other features. In other words the features are additive in their effect on the gulls' behaviour. This finding is consistent with the Law of heterogeneous summation, which holds that the independent and heterogeneous features of a stimulus situation are additive in their effects on behaviour.
The picture represents a hypothetical situation in which car manufacturers are competing for customers against each other.
In the middle of the picture is a row of four cars which compete in the UK market for a share of the market for small hatchbacks. They are shown in an arbitrary order of preference. This order could represents for example their market share, or an individual's order of preference.
The upper and lower sections of the picture shows the hypothetical effects
of altering the cost of two models.
In the example, if the cost of the Rover Metro was increased by £500 it would loose its lead on the preference scale against its nearest competitor - the Subaru Justy. In contrast if Volkwagen was to reduce the price of its Polo from £9,850 to £9,500 it would make ground on its nearest rival the Vauxhall Corsa.
Assuming the gull does not have a position preference, which egg do you think a gull would choose from each of the choices shown in this picture?
Remember that gulls:
An interactive version of this test is available here
The artificial flies used by anglers resemble the living insect in some important aspects -e.g. size, shape and colour.
But as every flyfisherman knows a particulat pattern of fly that works on one occassion may not catch a trout the next time it is presented. The effectiveness of the stimulus is affected by:
This example shows the importance of internal motivational factors in controlling behaviour.
This animation expands on the type of (static) diagram used in many textbooks to explain Lorenz's model
Konrad Lorenz developed a model that brings together the main ideas of classical ethology to explain animal motivation.
It should be emphasized that this is a model, it does not pretend to be an accurate picture of structures that actually exist within the brain. Instead it is a way of visualizing how various hypothetical systems work together to organize an animal's response to its internal and external environment.
It is called a hydraulic model because it views motivation as a liquid whose accumulation and discharge influences behaviour. consequently some people call it 'Lorenz's water closet'
Action specific energy (motivational energy) accumulates in a reservoir until released by an appropriate sign stimulus, represented by weights on a scale pan, or until the pressure on the valve causes an action pattern to occur spontaneously (vacuum activity).
The consummatory response or Fixed Action Pattern(s) released vary depending upon how much action specific energy is released from the valve.Points to ponder:
Although Lorenz's theory of motivation has been severly criticized, nevertheless it does suggest experiments and helps to explain some experimental results which we will now describe.Although Lorenz's theory of motivation has been severly criticized, nevertheless it does suggest experiments and helps to explain some experimental results which we will now describe.
According to Lorenz's theory the type of Fixed Action Patttern exhibited by an animal is a function of
Baerends and his colleagues have provided an elegant demonstration of this principle. Male guppies exhibit several Fixed Action Patterns in their courtship behaviour:
The external markings of a male guppy vary with its readiness to show courtship. In terms of Lorenz's model, the external markings are an indication of the level of action specific energy for courtship.
The sign stimulus value of the female increases with her size.
Baerends conducted experiments in which males with different external markings were exposed to females of various sizes. The results of these tests are shown below and indicate that
The next diagram shows the influence of the strength of external stimulation (measured by the size of the female) and the internal state (measured by the colour pattern of the male) in determining the courtship behaviour of male guppies.
Each curve represents the combination of external stimulus and internal state that produces the sigmoid courtship patterns of increasing intensity (After Baerends et al, 1955).
Examine the curve for sigmoid behaviour
Note how internal state and external stimulation have been operationally defined in this experiment
The person in this picture would eat ice-cream even if it was presented shortly after a meal, but wouldn't eat any of the other foods. But if 10 hours had passed since their last meal they would eat a beefburger if it was the only food available!
This diagram shows the effects of three different living conditions on aggression in cichlid fish.
Can Lorenz's hydraulic theory of motivation account for the increased aggression in isolated fish. One interpretation is that in the isolated male, aggressive action specific energy increases which must find an outlet and consequently the male becomes aggressive to the female he is living with. If this explanation can you explain why the total amount of aggression increases?
Point to ponder
What are the implications of this research for understanding and controlling human violence?
You may find some of the material from the course Integrative Topics in Psychology: Aggressionuseful
Deutsch's model addresses a fundamental weakness of Lorenz' Hydraulic mode. It includes a feedback link from the environment to the Analyser component which signals to the animal that its goal has been achieved. In turn the receptor system inhibits the Central link (shown in blue) and thereby the Motor link which is responsible for triggering behaviour is switched off.
The textbook by Slater gives a very good analysis of the strengths and weaknesses of Lorenz's model of motivation.
Andrew Giger is a neuroscientist working on bee vision. Part of his work involves training bees to discriminate between two different visual patterns. He wrote B-EYE as a tool to give him some idea what bees perceive. See the world through the eyes of a honey bee
I strongly recommend you look through Philip Lehners's book "Handbook of Ethological Methods", 2nd Ed, Cambridge University Press, 1996, if you are interested in reading a comprehensive discussion of ethological methods. He covers the lot! - How to select a behaviour to study, how to describe behaviour, how to record it, and how to analyse your data.
Here is a nice example of contemporary research in what is now called
'behavioural ecology' - a discipline that has its roots in ethology.
Dr Gilbert Roberts, (Department of Psychology, University of Newcastle) is interested in how vigilance behaviour decreases the risk of an animal being taken by a predator. He writes: "The ‘group-size effect’, a reduction in individual vigilance as group size increases, is one of the most widely reported findings in animal behaviour. However, there was concern expressed that studies had failed to take into account various confounding effects. I studied sequences of individual vigilance behaviour of crested terns during which flock size changes occurred. By pairing individual samples before and after flock size changes and by studying preening birds (where lower vigilance in larger flocks cannot be explained in terms of greater competition) I provided a much-needed, powerful test of how flock size affects vigilance. "
It is worth pointing out that the evolution of anti-predator measures was studied by the founding fathers of ethology over fifty years ago.
This topic could form the basis of an interesting third year project.
You can read an account of this research here: How individual behaviour responds to changes in group size
It is also worth reading Dr Roberts short description of his work on altruistic behaviour and the evolution of cooperationbecause this currently a 'hot topic' in sociobiology / evolutionary biology.