These proteins control

Outline and comment on the two schools of thought involved in the study of the nature-nurture debate in psychology. Explain, using examples, why this debate gives rise to so much controversy.” The debate concerning the influence of nature and nurture (or heredity and environment) on human behaviour is one of the longest running, and most controversial, both inside and outside psychology. It deals with some of the most fundamental questions that human beings ask about themselves, such as ‘How do we come to be the way we are?’ and ‘What makes us develop in the way we do?’ (Gross 2005, P.900)

There are three sides to the debate: on the nature side are the nativists or ethologists who believe that children develop almost entirely as a result of genetic influences, with their environment having little effect; on the nurture side are the behaviourists or empiricists who believe people are born as a blank slate which is ‘filled-in’ over a lifetime through learning and experience; and in the middle are the interactionists who, hence the name, believe children develop as a result of an interaction between biology and environment. I will now look at the arguments in more detail.

Genetic transmission is the way we acquire characteristics through inheritance. Each cell in the body contains a nucleus, which contains a substance called DNA. The main role of DNA molecules is the long-term storage of information. DNA is organised into long strands called chromosomes, and each chromosome is made up of thousands of genes. Genes are the basic unit of hereditary transmission and direct the way that growth and development happen within a plant or animal. Just after an animal is conceived, it is made up of a tiny group of cells. As these grow and divide, each gene acts as a code or set of instructions for making a particular protein.

These proteins control the cell’s internal chemistry and tell the cell what to do, giving the organism particular characteristics and determining the way its body functions. We inherit 23 pairs of chromosomes from our parents, 46 in all, half from our Mother and the other half from our Father. They combine to produce all the information an embryo needs to develop biologically. Since we inherit particular chromosomes through the egg and sperm, we also inherit the particular characteristics coded for by the genes on those chromosomes.

Arnold Gesell, a pioneer of developmental psychology, was an extreme nativist. He believed all individuals pass through the same genetically programmed series of changes, with the instructions for these changes being passed on at the moment of conception. “Gesell was mainly concerned with infants’ psychomotor development (such a grasping and other manipulative skills), and locomotion (such as crawling and walking)” (Gross 2005, P.901). Gesell established a research institute devoted to identifying ‘normal’ ages for a wide variety of behaviors and characteristics; he used a motion picture camera to film thousands of children in various stages of development. This genetically programmed series of changes is called maturation.

It is important to look at maturation as we try to understand genetic influences on behaviour. Some genetic influences are obvious at birth such as hereditary illnesses or abnormalities such as Down’s syndrome, but the things we inherit don’t necessarily show up all at once. “The physiological changes which take place during puberty, for example, arise because of genes that are present at conception, but they only happen when the body is mature enough for them to take place. In the same way, certain forms of behaviour may only emerge once the individual is mature enough” (Hayes and Orrell 1998, P.7).

In 1938 Lorenz and Tinbergen put forward four characteristics to identify directly inherited behaviour in animals. These are: stereotyped behaviour, which always occurs in the same way because behaviour which is directly caused by genetic influence can’t be affected by the environment; species-specific behaviour, because each species has its own genetic make-up the behaviour should differ to that of other species; the behaviour should appear in animals raised in isolation, because if it is truly inherited there should be no need to learn it; and the behaviour should appear complete even if the animal has not had chance to learn it.

In 1937, Lorenz used young geese to demonstrate that many preocial species (where the new-born animal is able to move around) form strong bonds with the first moving objects they encounter at a specific time after hatching or birth. Lorenz called this process imprinting because it was as though the geese had formed a powerful imprint of the object as if it was their mother. Lorenz saw imprinting being genetically ‘switched-on’ and then ‘switched-off’, believing this attachment must be formed during a critical period, or it wouldn’t happen at all. Further studies in imprinting have shown that the critical period can be postponed or extended by changing certain environmental factors. “This has led to some researchers (e.g. Sluckin, 1965) to propose instead the existence of a sensitive period: learning is most likely to happen at this time, and will occur most easily, but it may still occur at other times” (Gross 2005, P.545).

While psychologists like Gesell believed in the importance of maturation on children’s development, other psychologists emphasise the role of learning from environmental influences. Classical conditioning is a form of learning in which we come to associate a particular response with a particular stimulus because they have been linked together several times. An example of this we can all relate to is the ‘knee-jerk’ reflex experienced when your knee is tapped in the right place.

Russian physiologist Pavlov studied classical conditioning in great detail. In 1927 he conducted an experiment on the digestive process in dogs. He developed a technique for collecting dogs saliva in a tube attached to the outside of the dog’s cheek. Pavlov noticed that the dogs would start salivating at the mere sight of the food bucket or the sound of the laboratory assistant’s footsteps that were coming to feed them. From this he predicted that, if a particular stimulus in the dog’s surroundings was present when the dog was presented with food, then this stimulus would become associated with food and cause salivation on its own. To begin with, Pavlov associated bells with giving the dogs to their food and, after doing this on several occasions, the dogs started to salivate in response to the bell. The reflex of salivation had become conditioned. The stimulus (the bell) became a conditioned stimulus as a result of regular association with the unconditioned stimulus (the food).

In 1924, Watson, an extreme behaviourist, argued that if he were given ‘a dozen healthy infants…and my own specified world to bring them up in, and I’ll guarantee to take any one at random and train him to become any type of specialist I might select – doctor, lawyer…and yes, even beggarman and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors’ (Hayes and Orrell 1998, P.2).

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