Nature vs nurture

Nature

- Refers to inherited influences, or heredity. Argues all human characteristics- and even some aspects of knowledge- are innate. Psychological characteristics like intelligence or personality are determined by biological factors (genes), just as physical characteristics like eye colour or height are

Nurture

- Refers to the influence of experience and the environment. Argues that the mind is a blank slate at birth, which is then shaped by the environment. This view later became an important feature of the behaviourist approach

- Lerner (1986) identified different levels of the environment. This includes prenatal factors, such as how physical influences (smoking) or psychological influences (music) affect a foetus. More generally, development is influenced postnatally in terms, for example, of the social conditions a child grows up in

Measuring nature and nurture

- The degree to which two people are similar on a particular trait can be represented by a correlation coefficient and is called concordance. Such concordance provides an estimate about the extent to which a trait is inherited- called heritability

- Heritability is the proportion of differences between individuals in a population, with regards to a particular trait, that is due to genetic variation. A figure of .01 (or 1%) means gene contribute almost nothing to individual differences and 1.0 (100%) means genes are the only reason for the individual differences

The interactionist approach

- Environment and heredity interact. For this reason, psychologists are more likely to ask what the relative contribution of each influence to our behaviour is. Therefore, the nature-nurture debate is really about discussing how nature and nurture interact

Diathesis-stress model

- This suggests behaviour is caused by a biological or environmental vulnerability which is only expressed when coupled with a biological or environmental 'trigger'. For example, a person who inherits a genetic vulnerability for OCD may not develop the disorder. But, combined with a psychological trigger (e.g. a traumatic experience) this may result in the disorder appearing

Epigenetics

- Refers to a change in our genetic activity without changing the genes themselves. It is a process that happens throughout life and is caused by interaction with the environment. Aspects of our lifestyle or events we encounter (from smoking and diet to trauma and war) leave 'marks' on our DNA, which switch genes on or off. This explains why factors such as smoking have a lifelong influence even after you stop- they have changed the way your genes will be expressed

- These changes may go on and influence the genetic codes of our children, as well as their children. This introduces a third element into the nature-nurture debate- the life experience of previous generations

Evaluation of the nature-nurture debate

- One strength is through the use of adoption studies. These are useful because they separate the competing influences of nature and nurture. If adopted children are found to be more similar to their adoptive parents, this suggests the environment is the bigger influence. Whereas, if adopted children are more similar to their biological parents, then genetic factors are presumed to dominate. A meta-analysis of adoption studies by Rhee and Waldman (2002) found that genetic influences accounted for 41% of the variance in aggression. This shows how research can separate the influences of nature and nurture

Evaluation of the nature-nurture debate

- A strength is that it has real-world application. Research suggests that OCD is a highly heritable disorder (Nestadt et al (2010) put the heritability rate at .76). This means that people who have a high genetic risk of OCD because of their family background can receive advice about the likelihood of developing the disorder and how they might prevent this (e.g. learn to manage stress). This shows that the debate is not just a theoretical one but that it is important, at a practical level, to understand the interaction between nature and nurture

Weakness of nurture

• The nurture side of the debate cannot account for individual differenceswithin children raised in the same family environment

  • One child may turn to crime while the other child never breaks the law

  • One child may develop a drug addiction while the other child does not

Weakness of nature

Twin studies have failed to show 100% concordance between MZ (identical) twins across a range of studies e.g.

• McGuffin et al. (1996) found that MZ twins showed a 46%concordance rate for depressioncompared to 20% in DZ (non-identical) twins