Download The Nature Nurture debate

The Nature Nurture or Heredity vs. Environment debate
This debate is concerned with the extent to which our genes and environment contribute to producing
human psychological characteristics, that is all the behavioural and cognitive traits people can have, e.g. IQ,
sense of humour, aggression, depression, cheerfulness, optimism and competitiveness etc.
History of the nature-nurture debate
Nativism – (innate) is of the view that nature, i.e. our genetic makeup, determines certain abilities and
behaviours. Descartes in the early 1600’s argued this.
Empiricism – (environmental) the view that at birth the human mind is a ‘tabular rasa’ (blank slate) which is
filled through learning and experience. Locke argued this in the late 1600’s.
Interactionist – the now favoured proposal that both nature ad nurture combine to produce our
psychological characteristics. Therefore, it is more appropriate to ask “how much do they contribute?” and
“in what way do they interact”? For example, Plomin et al (1997) showed that personality characteristics
such as neuroticism and assertiveness have a heritability coefficient between 0.15 and 0.50. If a value of
0.1 means the trait or characteristic is determined solely by genetics and a value of zero that genetics
plays no role at all and that the environment is the sole determinant, then this means what?
What do we really mean by nature?
We mean inheritance. The genetic material that is passed from parents to offspring causes psychological
characteristics to be developed. Usually the focus is on how these cause individual differences as opposed
to what makes humans different from other animals but it can mean both.
For example, the ability to be able to use language occurs with only the bare minimum of environmental
factors present, i.e. other language users around, and so it can be said we use language naturally. However,
how good we are at this compared to others may be due to environmental factors as well as genetics.
What do we really mean by nurture?
Traditionally this has three possible descriptions:
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Influences that occur outside the individual
Postnatal influences
Influences that affect the individual who is passively shaped by them
Do you think this is an accurate account of nature?
The environment could also be divided into biological environment and psychological environment. The
biological environment affects our physical development and would include such things as malnutrition and
drug abuse by the pregnant mum. The psychological environment includes a person experiences such as the
quality of the relationship between child and socio-economic status.
However
The three descriptions of nurture above may be inaccurate. Take the following examples:
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Alcohol is toxic to brain cells during the first 10 weeks of pregnancy.
Unusual hormone levels in the womb may affect the development of certain brain areas
Humans interact with their environment affecting it and themselves.
List all the topics in psychology that you can think of that have been related to the nature-nurture debate.
Using an example from psychology, explain what is meant by the nature-nurture debate.
(4 marks) [4 marks: AO1 = 2, AO2 = 2]
In what ways do nature – nurture interact?
The contribution of nature
The most common way to understanding the contribution of nature and nurture is by looking at twin studies.
Monozygotic (identical) twins share exactly the same genetic makeup. Dizygotic (fraternal or nonidentical) twins share 50% of the genes, just like ordinary brothers and sisters. The degree of similarity
between monozygotic twins than Dizygotic twins is often taken as an indication of genetic influence.
Twin studies have been conducted looking at intelligence, temperament and mental illnesses such as
schizophrenia and have demonstrated a clear genetic influence in each case (Gottesman, 1991).
However, can you think what else should be considered when rating, i.e. the intelligence of monozygotic
twins?
Also think about how height is genetic, but what about the fact that Americans and Europeans have
increased in height by over 5cm’s between 1920 – 1970. Why was this?
Problems with measuring intelligence using IQ tests may be inaccurate. For example, they only measure
certain aspects of intelligence, and practice at them will improve performance which could indicate a higher
level of intelligence than someone who had never completed an IQ test before.
The contribution of nurture
The use of twin studies, particularly monozygotic twins is also useful when understanding how much
behaviour is due to the environment. Identical twins reared together are assumed to have the same
upbringing, or do they?
1. Reactive ‘gene – environment’ correlations (or how people affect their environment)
Aggressive children tend to evoke aggressive responses and therefore experience aggressive environments.
The same goes for children with a sunny disposition. So the genetic influences that produce aggression in a
child therefore interacts with their environment to affect it, hence the use of the term ‘reactive’.
An example of a static ‘gene-environment’ correlation could be how an individuals biological make-up e.g.
gender, affects how people respond to them. This is a fixed characteristic hence the term static (Rutter
and Rutter 1992).
2. Shared and non-shared environments
Often the environment people live in is correlated to a personal characteristic, e.g. how low socio-economic
class is associated with a higher incidence of schizophrenia. Within a family, siblings have a shared
environment, yet they are rarely very similar in psychological characteristics. This may suggest that nonshared environments or experiences are most important in the development of psychological
characteristics.
Even within the same family children have non-shared experiences, e.g. maybe one is treated more strictly
that the others, the youngest could always be viewed as being spoiled or the middle could always feel like
they are left out. Dunn and Plomin (1990) argue that the only way family influences could affect behaviour
is if each child experiences events differently. They call these differences in how family members are
treated ‘relative differences’.
Plomin and Thompson (1987) suggest that providing a child is brought up in a good enough, supportive, nonabusive or neglectful environment the actual family has little impact on the individuals personality or
intellect (Gross, 2003). These different experiences within a family are called micro-environments – a
very specific environment to that individual.
3. How we construct our environment
“Different people, at different developmental stages, interpret and act upon their environments in
different ways that create different experiences for each person. In this view, human experiences are a
construction of reality, not a property of a physical world that imparts the same experiences to everyone
who encounters it” (Gross, 2003).
Scarr (1992) proposed that nothing is real; realities are the product of how things get represented and
reacted to. What this means is that how we perceive events, how we understand what is happening around
us, makes us see the world in a particular way.
Consider the following:
What is real?
A beer glass is full or half empty
You start a new job – it’s challenging or its frightening
You win the lotto - £50 Yeaaahhhh! Or not so great?
4. Vulnerability
Horowitz developed a model of how an individual and their environment interact and how this can affect
development.
A thirty year longitudinal study beginning in 1955 demonstrates this interactionist viewpoint. The study
was conducted by Werner in Hawaii on 700 children. She classified the children by many different factors
and amongst other conclusions found that the children with certain temperaments could be very successful
despite a poor environment.
What do you think would constitute a facilitative environment for any child?
How much do nature and nurture each contribute?
Jones ’93 cited in Gross 2003 suggests that nearly all inherited characteristics involve gene and
environment acting together and it is impossible to sort them out into compartments. People see
characteristics i.e. intelligence, as a ‘cake’ and then try to slice it to show how much gene and how much
environment was involved. In fact the two are so closely blended that trying to separate them is more like
trying to unbake the cake.
Schizophrenia and the nature nurture debate
The DSM IV criteria describes schizophrenia as having two or more of the following symptoms for 6
months + leading to a deterioration in social and work life.
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Hallucinations – mostly auditory
Delusions – bizarre beliefs and thoughts about the world
Disorganised speech
Catatonic behaviour – repetitive movements or gestures
Negative symptoms – flat, unresponsive
Using the handout – Explanatory theories of schizophrenia complete the table below:
What evidence is there for nature?
What evidence is there for nurture?
Can we conclude schizophrenia is due to nature? NO!!!
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The concordance rate in all MZ studies are always less than ______% (_____% would be the rate
if it was purely down to genes, therefore there must be other ____________ involved.
For example____________________________________________________________.
Finally twin studies often show a wide variation in results, e.g. Fisher (1973) found a concordance rate of
only 24% in MZ twins reared apart.
Other problems include?
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Schizophrenia is a name given to a group of disorders which may have quite different symptoms.
Only some types of schizophrenia may have a genetic link.
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By focusing on genetics, one can be criticised for adopting a _______________ approach. This is
when we try and explain an aspect of human behaviour by looking at only ______ single factor and
in this case ___________.
Perhaps it is better to utilise the __________ - stress model which states that when considering why
certain people develop schizophrenia, it is important that we do not only consider their ____________
vulnerability to a disorder (diathesis) but we must also consider ____________ stressors. Therefore if a
person is biologically predisposed to develop the disorder if they have a good _____________ they will
not do so.
Can we conclude that schizophrenia is due to nurture? NO!!!
Families are analysed _______________________ (looking back, long after mental disorders have
surfaced); Faulty communication patterns may be the result of living with schizophrenia rather than the
cause.
There is difficulty in explaining why schizophrenia develops in some but not all children within the
_________ family as it is expected that communication systems would be similar between all members of
the family.
Diathesis stress model - need to consider both ___________ and the ___________.
AO1 One mark for outline of nature-nurture, e.g. nature is that which is inherited/genetic as distinct from
nurture which refers to all environmental influences after conception, i.e. experience. One mark for the
debate, i.e. the controversy within psychology that is concerned with the extent to which particular
aspects of behaviour are a product of either inherited or acquired characteristics.
AO2 Up to two marks for the application of the nature-nurture debate to an example in psychology. One
mark for an appropriate example; Possible examples could come from perception, sex-role behaviour,
atypical behaviour or differences between individuals in IQ. One mark for an application of the debate to
the example.