The very well known ‘nature versus nurture’ debate aims to establish to what degree particular human attributes are caused by genes and to what degree by environment (although this is an oversimplification as many human attributes come about as a result of how these two factors interact).
If you are like me and had a traumatic childhood, you may, also like me, often wonder to what extent the person you are today has been formed by your genetic inheritance and to what extent by the traumatic environment in which you grew up.
Psychologists determine the relative effects that our genes and our experiences have on us in relation to specific characteristics by conducting what are known as ‘twin studies’ (although it is not necessary to explain what these are here).
Such studies have revealed the following findings (these were originally published by Robert Plomin, 1990).
I will list the best estimates we currently have at our disposal of the relative effects of genes and environment on the following categories of human attribute/behaviours/characteristics :
1) MENTAL ILLNESS
3) BELIEFS AND ATTITUDES
Let’s look at each of these four categories in turn:
1) MENTAL ILLNESS :
Major depression – approx 60% environmental, 40% genetic
Mild depression – approx 90% environmental, 10% genetic
Schizophrenia – approx 52% environmental, 48% genetic
Anxiety disorder – approx 90% environmental, 10% genetic
2) PERSONALITY :
Overall personality – approx 70% environmental, 30% genetic
Emotionality – approx 60% environmental, 40% genetic
Extraversion – approx 65% environmental, 35% genetic
Neuroticism – approx 70% environmental, 30% genetic
Socialibility – approx 75% environmental, 25% genetic
3) BELIEFS AND ATTITUDES :
Religiosity – 100% environmental, 0% genetic
4) RELATIONSHIPS :
Male homosexuality – many studies on this are flawed, but the most valid suggest that male homosexuality is nearly entirely ENVIRONMENTALLY DETERMINED (and therefore has very little to do with any genetic factors, eg. Bailey, 1999).
Female homosexuality – approx 87.5% environmental, 12.5% genetic
Male mate type preference – approx 100% environmental, 0% genetic
Attachment security – approx 100% environmental, 0% genetic
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David Hosier BSc Hons; MSc; PGDE(FAHE).
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