Behaviour – Nature or Nurture?
The basis of the debate
Since antiquity, philosophers and scientists have been fascinated by the development of living creatures. What began as a philosophical debate over the roles of innate versus environmental contributions to the final behaviour of the organism has become an increasingly active area of scientific study. The nature/nurture controversy is a debate about whether human behaviour is determined primarily by genetic or environmental factors, which touches on psychology, linguistics, and other social sciences.
Instinctive versus innate contributions
Most behaviour has elements of both inheritance and training, yet each must make a distinct contribution and separating these is often difficult. Vision is case a case in point, since although an animal is born with eyes, it must mature in the use of them and learn to see. This case is one, however, in which the distinction between the iinstinctive and learnt components has been examined intensely. In 1925, Robert Matthey severed the optic nerve of an adult newt, which managed to recover its vision within thirty days. This incredible result, that the animal had re-established the complex network of nerve-fibres between the eye and the brain, was confirmed by later experimentalists. However, this result also poses an interesting question: whether the newt relearns how to see, or whether its heredity, forming and organising the regenerating nerve fibres according to a genetic pattern, automatically restores orderly vision. By rotating the eyes of frogs through angles between 0° and 360°, experimenters determined that the animal always regenerated an organised pattern of vision although the visual field as a whole might be turned upside down, or inverted on some other axis, or indeed displaced from the left to the right side. The conclusions drawn from these results were that, in the lower invertebrates at least, many features of visual perception are built into the organism and do not have to be learnt.
Instinctive behaviour in animals
Dragonfly nymphs also instinctively ‘know’ how to fly; even though they have spent their entire lives underwater and have never previously used wings. In spite of this, the action of flying is carried out with perfection the very first time it is attempted. This is an example of innate behaviour, ‘a pattern of inherited, pre-set behaviour that does not require learning or practice’, which lends credence to the view that nature is important in determining behaviour. Instinctive behavioural patterns have developed under the influence of natural selection and hence alleles that produce behaviour conferring a selective advantage have become more common among animal populations.
Genetics
It is certainly true that, since all of the components of the brain are coded for by cellular DNA, genetics does have a strong influence on behaviour. However, it is not easy to be absolutely sure that a particular pattern of behaviour is entirely innate. Much of animal behaviour is the result of interactions between the animal’s genes and its environment and since the discovery by researchers on the Human Genome Project that humans have only 30,000 genes, about ten times fewer than was expected, it seems likely that environmental influences play a greater role in our development than was previously acknowledged. Dr. Craig Venter, president of Celera Genomics stated in 2001 that “we simply do not have enough genes for this idea of biological determinism to be right.” and it is clear that understanding how a relatively small number of genes translate into the incredible complexity of a human being will be one of the challenges of future geneticists.
Virgil - transfer between sensory systems
In his book An Anthropologist on Mars, Dr. Oliver Sacks drew attention to the case of a man named Virgil who had been blind since childhood as a result of ocular cataracts. When these were removed, the sudden restoration of sight overwhelmed his visual cortex which responded by suddenly shutting down.
In the end, although the physical appearance of his retinas remained the same, Virgil's visual perception deteriorated and he became as blind as he had been before his operations, although he experienced rare moments when he could see something accurately. This ultimate loss of vision related to excess sensory stimulation makes it clear that nurture plays a major role in our ability to make sense of visual stimuli and that even if an alternative tactile mode of object identifications is developed, conceptual information does not appear to transfer readily between the two sensory systems.
Experience
Some animal behaviour consists of a basic pattern, which is innate but can be modified by experience. Examples of such behaviour include the tendency for crocodiles to incubate their eggs at the temperature at which they had experience in their own egg or of ichneumon flies to lay eggs in the caterpillars from which they themselves had developed. Such behaviour combines the advantages of rapid, automatic behaviour with the flexibility which is born of experience. Associative learning also involves the superposition of innate and learnt behaviour, as shown in Skinner’s investigation into operant conditioning.In this experiment, an animal’s instinctive desire for a reward is attached to the performance of a certain action through association in the animal’s brain.
Arguments from extremes
Obviously if two animals from different species, human and chimpanzee for example, are both nurtured under identical environmental conditions then the child’s behaviour will be radically different from that of the chimpanzee and this difference will be almost entirely caused by genetic discrepancies between the two organisms. Arguing from this extreme, the proponents of the Nature side of the argument would have us believe that intraspecific differences in behaviour are comparable to these interspecific differences in behaviour, which are caused entirely by genetic inheritance, except to a lesser degree. Similarly, if genetically identical twins, are brought up under divergent conditions then the behavioural differences between them will be profound, and caused totally by environmental disparities. Arguing from this extreme, the proponents of the Nurture side of the debate would have us believe that differences in human or animal behaviour stem wholly from environmental factors in the same way as the differences in the twins’ behaviour. In this way, it can be seen that situations can be devised that will demonstrate that either nature or nurture are predominant in certain circumstances. The most obvious conclusion to draw from this data is that both nature and nurture are important in the development of a human being.
Nativism versus empiricism
In the seventeenth century, the French philosopher René Descartes argued that people possess certain inborn ideas that enduringly underpin people's approach to the world. The British philosophers Thomas Hobbes and John Locke, on the other hand, took a more empirical approach, emphasising the role of experience in the formation of future behaviour.
Conclusion
In recent years, controlled experimentation and the observation of natural processes, in both human and animal subjects, have led away from both nativist philosophical views, which stressed heredity over environment, and empirical views, which stressed environment over heredity. Modern geneticists' theories tend to view the development of behaviour as a synthesis of both components, each indispensable to the attainment of normal patterns of behaviour.In the end, the question of whether nature or nurture is more important is unlikely to be answered positively one way or the other since such effects cannot be quantitatively measured. Behaviour is dependent on complex interactions between genetic and phenotypic characteristics and environmental factors. As a result of this, it is impossible to say that either nature or nurture is more important in determining behaviour.
BIBLIOGRAPHY
Mammalian Physiology and Behaviour – Jones & Jones
The Five Kingdoms & Behaviour – Avery, Cuthill, Miller & Rowland
An Anthropologist on Mars – Oliver Sacks
The Blind Watchmaker – Richard Dawkins