1. Biological Approach Unit 8 Psychological Perspectives

2. Biological Approach All behaviour is caused by genetic and biological influences Genetics Structure of the brain Neurotransmitters Hormones

3. Hormones During puberty levels of testosterone increases in boys Testosterone is linked to aggression During the menopause oestrogen levels significantly drop in women Lack of oestrogen is linked to depression in women

4. How can the influence of genetics be tested? By comparing the behaviour of twins Why?

5. Why are we interested in twins? We can study the genetic basis of behaviour If a behaviour is caused completely by genetics then both identical twins should share the same behaviour as they have 100% the same genes If a behaviour is caused completely by genetics then some sets of non identical twins will share the behaviour but some sets of non identical twins will not as they only have 50% the same genes

6. Monozygotic twins (MZ) Commonly known as identical twins They occur from a single egg which is fertilised This forms one zygote (a fertilised cell) The zygote divides into two separate embryos These embryos develop into foetuses sharing one womb MZ twins are identical genetically sharing exactly the same DNA

7. Monozygotic twins (MZ) Around 1 in 50,000 pregnancies result in conjoined twins This may be because the zygote divides too late (~13 days or later)

8. Dizygotic twins (DZ) More commonly known as non-identical twins Occur when 2 eggs are fertilised by 2 different sperm cells Genetically they share 50% of their genes and are therefore just like ‘ordinary‘ siblings

10. Causes of Anorexia Genetics Some biological theorists suggest there is a genetic component involved in developing anorexia A person is 6 times more likely to develop an eating disorder if they have a relative who is a sufferer of an eating disorder (Strober et al, 2000)

11. Holland et al (1984) Twins Research Compared rates of Anorexia in identical twins compared to non identical twins Concordance rates – the percentage of times both twins suffered from AN Identical twins – 55% Non identical twins – 7%

12. http://www.youtube.com/watch?v=AbtX5 xOCpq8