Genes can be recessive or dominant. For example: The gene that gives the colour in brown eyes is a dominant gene and the blue gene that results in blue eyes is a recessive gene. A child will have brown eyes if one of its parents had brown eyes even if the other parent had blue eyes. That child will still have the blue-eyed gene and may pass it on to the next generation (Hayes and Orrell 1996, pg 5).
Some diseases are inherited mainly because of faulty genes. For example: Huntingdon disease is caused by a faulty gene and causes premature degeneration of the brain (Barber M et al 2000,pg 504). Down’s syndrome is another example of a genetic disorder, which has resulted from the presence of an extra chromosome and causes physical and mental handicaps to different degrees of severity (Hayes and Orrell 1996, pg 4).
As well as inherited characteristics and features there is also evidence of inherited behaviour. This was shown in 1938 in Lorenz and Tinbergens 4 characteristics in animal behaviour: -
Stereotyped - this behaviour happens the same way every time.
Species specific - this behaviour is specific to a certain type of animal.
Isolation - this behaviour is the same as others of their species, even if they have been isolated.
No practice - this behaviour appears as a complete unit even if the animal has had no chance to practice it. (Hayes and Orrell 1996 pg 9 & Class notes)
Imprinting is a type of behaviour that can form rapid attachments and is also believed to be genetically influenced. For example: Ducklings had become imprinted on a human being. Lorenz found that ducklings would adopt him if he were the first moving thing they saw. He believed this would only take place in the critical period, up to 25 hours after hatching. This was questioned by, (W Slucking in 1964.) After his own study of the same experiment, he found the period was extended if the ducklings were isolated from one another, and hadn’t been able to imprint on each other (Hayes N 1993, pg 39).
Behaviours we inherit don’t show up all at once. Certain forms of behaviour emerge when the individual is mature enough. This is known as maturation, for example, the physiological changes that take place in puberty (Hayes & Orrell 1996 pg 7). There are disagreements between the nativists and behaviourists about whether or not maturation is purely genetic. (Hayes N 1993, pg 32).
This brings the debate to the other side of the disagreement and behaviourists also known, as empiricists, believe nurture is the main influence in development. In 1913, J.B. Watson attempted to make psychology `Scientific`. Previously psychology had concentrated on the study of the mind, Watson argued that the mind was not suitable for valid scientific research, so instead he studied behaviour (Hayes N 1995, pg 3). Watson was a total empiricist believing the environment was the only important factor in an individual’s development. He considered that a child was born as tabula rasa – a blank slate, which experience would write upon to produce the person (Hayes & Orrell 1996, pg 2.
On a different point Watson believed the stimulus-response theory would eventually lead to a complete understanding of human behaviour (Hayes N 1995, pg 23). In 1911 E.L. Thorndike argued that some responses learned were not just because they were associated with the stimulus-response but were produced from pleasant consequences. (Hayes & Orell 1996,pg19). Stimulus-response is a primitive form of learning which associates a particular response with a particular stimulus, because they have been linked together several times. Ivan Pavlov’s work on conditioned reflexes came together with Watson’s stimulus-response work and became known as classical conditioning (Hayes N 1994, pg 59).
Animals have conditioned reflexes like knee jerking, sneezing, hiccupping and salivation. (Class notes) Pavlov’s salivating dog experiment was the first response he investigated when he discovered classical conditioning. (Hayes & Orell 1996,pg 15). He showed he could make the dog salivate without the presence of food using a bell. Classical conditioning in a medical setting can also be used to reduce fear and anxiety.
The second type of conditioning is Skinners operant conditioning previously known as the law and effect. Skinner investigated positive and negative reinforced behaviours. For example: The Skinner box - a rat would be placed in a box with only a light, lever and a food delivery chute. When the rat eventually pressed the lever he would be rewarded with food. This resulted in the behaviour of lever pressing being strengthened and reinforced. In other experiments negative reinforcement by pressing the lever was used for a rat to escape or avoid something unpleasant like an electric shock. There was no food reward; the reward was not getting shocked (Hayes & Orell, 1996, Pg20). Schedules of reinforcement for strengthening learning were used so learning was not lost and the reinforced behaviour continued. The schedules were continuous, fixed interval, variable interval, fixed ratio and variable ratio. The variable ratio had a high ratio of response and a high resistance to behavioural extinction. (Hayes N 1994,pg65).
Controversial issues expanded on the nature-nurture debate, one of which is the theory of aggression, which is suppose to be instinctive in us all. Other theories consider aggression arise as a result of environmental circumstances. Freud and Lorenz saw aggression as an instinctive drive. One example of this is Lorenz’s tank like human. He saw aggression as a continuous source of energy, which would fill the tank and be released when it overflows. Rose et al; disagreed with aggression being inherited and other studies suggest that aggression arises from a response to frustrating circumstances and also learning by imitation. Individuals that had been exposed to aggressive behaviour in the past will probably be more likely to react aggressively in a frustrating environment. (Hayes & Orrell, 1996 pp39-44).
Interaction between genetic influences and environment are not mutually independent of one another. This is explained in Hebbs example in 1949 with his `Egg` analogy. If genetics in the egg are absent there will be no egg, but if the warm supporting environment was removed the egg will die, there for nature cannot be distinct from nurture (Hayes N 1995, pg 138).
There is one distressing story that is happening now in medical circumstances that I feel is important to the nature versus nurture debate. This story has been controversial to the point of tragedy. In 1966 a medical accident happened involving the circumcision of a boys penis. Bruce Reimer was born a boy in Canada in 1965. He was to have routine surgery, which went horribly wrong. Psychologist John Money took up his case and suggested that Bruce should be raised as a girl. John wanted to prove nurture would over-ride nature in gender identity. Bruce was castrated and called Brenda. Brenda still behaved and felt like a boy even though he did not know he was a boy. The nurturing of Bruce’s parents and environment had little effect in changing his gender identity even though it was thought of as successful. In adult hood he had reconstruction surgery after his parents told him the truth and later married and raised children successfully. He sadly committed suicide on May 4th 2004. This suggests in this case nurture cannot over ride nature. (T.V Documentary & Radio Times)
There are many debates and examples that give rise to much controversy in the nature verses nurture debate in the development process. In my opinion this is one debate that psychologists will never be able to resolve, as there is strong evidence in certain circumstances, to support each debate, that nature and nurture both influence development.
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HAYES N, (1994) Principles of comparative psychology. East Sussex: Lawrence Erlbaum associates LTD.
BARBER M et al, (2000) Biology. London: Collins Educational.
HUDSON G, (30oct-5nov 2004) Horizon BBC2. Southwest: Radio times.
