1. Session 8 Genetic Influence on Behaviour

2. What do attached ear lobes, blue eyes, and tongue-rolling have in common?

3.  Many researchers also believe that genes influence a wide range of human behaviour.  Research on psychology and behaviour is increasingly incorporating genomic studies.

4. What are genes? Is behaviour predetermined by our genes? How can we study this?

5. What exactly is a gene?? https://www.youtube.com/watch?v=aOU4hzR3w-A

7.  Create your own Venn diagram of behaviours that you share with one/all of your parents/siblings  Discuss which traits you think you have genetically inherited and which traits you think are a result of your environment

8. Virtually all behaviour is influenced by genes. Virtually no behaviour is determined by genes.

9.  Genes influence behaviour indirectly.  There is usually more than one gene involved in a behaviour  Genes influence the production of proteins that affect the anatomy (e.g. brain structure) and physiology (chemical processes) of the body  Some behaviours are more genetically influenced than others  There is an interaction between environmental, biological, cognitive and genetic factors in the development of behaviour

10. https://www.youtube.com/watch?v=uvk2g9hJMTs

11. Correlations show the relationship between two variables. There is no manipulation of an IV, so cause and effect are not established. A correlation of +1.0 means as x increases, y increases (positive correlation). -1.0 means that x increases, y decreases (negative correlation). In twin research, we expect to find a higher correlation than when comparing a child to someone outside of the family. -1 ----------------0------------------ +1 -1 ----------------0------------------ +1

12.  If a correlation is found it is called the concordance rate -1 --------------0--------------- +1

13.  Researchers use correlational research to establish a genetic argument for the origin of human behaviour

14. 1. Monozygotic (MZ) ◦ Fertilized from one egg that splits in two  Identical (share 100% of their genes)

15. 2. Dzygotic (DZ) ◦ Fertilized from two eggs  Brothers and sisters (share 50% of their genes)

16. Comparing Monozygotic twins (MZ) with Dzygotic twins (DZ). Since MZ twins have identical DNA, there should be a higher concordance rate. Comparing MZ twins reared together vs. MZ twins reared apart. Why might this be better than the first technique?

18.  Twin studies have produced a great deal of data in support of biological roots of disorders; this has helped psychologists to stress prevention for those who are vulnerable to such disorders.  There is a high cross-cultural reliability of concordance levels.

19.  MZ twins are rarely separated at birth and raised in a totally different environment, yet this is really necessary to substantiate claims. MZ twins reared together share many of the same experiences. DZ twins reared together may not share the same experiences due to levels of attractiveness or temperament.

20.  Adoption studies tend to compare the adopted child with the biological mother and the adoptive mother to determine which has the higher concordance rate for a given behaviour.  Why might adoption studies at times be preferrable to twin studies?

21.  Adoption studies allow researchers to isolate variables.  If a biological mother has no contact since birth and still matches for a specific trait - for example, the adopted child’s IQ is better than the adoptive mother and in concordance with the birth mother - this is strong evidence that genes play a significant role in the development of this trait.

22.  Selective placement is a problem. Babies tend to placed with families similar in background to the natural parents.  Adopted children – as well as twins - are not representative of all children.  The act of being given up for adoption may affect the child’s behaviour.

23.  ½ genes from Mother  ½ genes from Father  Brothers and sisters share 50% of genes  Grandparents share 25% with grandchildren  Cousins share 12.5% with one another

24.  Which of the following do you think might be inherited? Why?  Intelligence  Depression  Risk-taking behaviour  Homosexuality  Problem solving skills  Agoraphobia

25.  Read through pages 52-56 of your textbook about genetic research and intelligence  Make a note of anything important then arrange this into a mind map of how you would respond to the question in an exam With reference to relevant research studies, to what extent does genetic inheritance influence behaviour?

26. Conclusion: refer to WHAT EXTENT genes influence not just what they influence Evidence 2 Evaluation of evidence 2 Evidence 1 Evaluation points for evidence 1 Introduction: What are genes? Why do researchers study genes? Is there a link? What behaviour will you be talking about? Refer to “TO WHAT EXTENT” With reference to relevant research studies, to what extent does genetic inheritance influence behaviour?

27. .

28.  Genes influence behaviour indirectly.  There is usually more than one gene involved in a behaviour  Genes influence the production of proteins that affect the anatomy (e.g. brain structure) and physiology (chemical processes) of the body  Some behaviours are more genetically influenced than others  There is an interaction between environmental, biological, cognitive and genetic factors in the development of behaviour

29.  Read through pages 52-56 of your textbook about genetic research and intelligence  Make a note of anything important then arrange this into a mind map of how you would respond to the question in an exam With reference to relevant research studies, to what extent does genetic inheritance influence behaviour?

30. Conclusion: refer to WHAT EXTENT genes influence not just what they influence Evidence 3 Evaluation of Evidence 2 Evidence 2 Evaluation of evidence 2 Evidence 1 Evaluation points for evidence 1 Introduction: What are genes? Why do researchers study genes? Is there a link? How do we study genes? What behaviour will you be talking about? Refer to “TO WHAT EXTENT” With reference to relevant research studies, to what extent does genetic inheritance influence behaviour?

31. Introduction 1. State what you are doing in the essay: i.e. consider the extent to which genetic inheritance influences behaviour. 2. Outline the overarching principle: ◦ According to one of the principles of the biological level of analysis, behaviour is innate and inherited because it is genetically based (we are predisposed to a specific behaviour due to genetics).

32. Introduction 3. Describe genetics and the importance of research into genetics: ◦ It is argued by some researchers that people have a genetic predisposition for some behaviours. ◦ Genes are segments of DNA inherited by the offspring from the parent. ◦ Behavioural Genetics = the understanding of how genetics and environment contribute to individual variations in human behaviour, where the premise is that the inheritance of DNA influences behaviour. ◦ Genetics alone do not affect behaviour- environmental factors also involved ◦ Genes are complex  It is unlikely that a single gene is responsible for such complex behaviours as schizophrenia, intelligence or depression.  There is no causal relationship between a single gene and a specific behaviour.

33. Introduction 3. Describe genetics and the importance of research into genetics: ◦ It is thought that what is inherited is the gene that can lead to the development of the specific behaviour, not the behaviour itself.  This means that an individual may have a genetic predisposition to a behaviour but without appropriate environmental stimuli, the behaviour will not be manifested

34. 4. Describe type of studies used in genetic research ◦ Twin studies  Used in genetic research to study the correlation between genetic inheritance and behaviour due to the common genetics shared by twins.  Monozygotic twins (MZT) identical - share 100% genetic material.  Dizygotic twins (DZT) fraternal - share 50% genetic material.  It is usually further explored, by studying the twins either separated or together to make a correlation of their behaviour. ◦ Adoption studies  Allow researchers to study the comparison between genetic and environmental influence on behaviour.  Adopted children share no genes with their adoptive parents but 50% of genes with their biological parents. ◦ Family studies  Study behaviour between family members who have similar genetics to different degrees. Inheritance

35. 5. Outline behaviour you are looking at: Intelligence ◦ Intelligence is an aspect of behaviour that has been studied in relation to genetics. ◦ It has been questioned whether intelligence was attributed to genetic or environmental factors. Intelligence is difficult to define ◦ IQ tests were developed by a French man called Binet to measure of intelligence and are used in much psychological research.

36.  And then finally onto the body of the essay...

37. Bouchard and McGue (1981 Bouchard and McGue (1981) siblings.  Conducted a meta-analysis of 111 studies of siblings.  Investigated IQ correlations between siblings.  Found that there was a positive correlation between kinship and IQ correlation - the closer the siblings were, the more similar their IQ.

38. Bouchard and McGue (1981 Bouchard and McGue (1981) ◦ Large study, so generalisable. ◦ However, siblings are raised in the same environment, so influence may not be purely genetic, and it is difficult to differentiate between influence of genetics and environment. In order to investigate the role of genetics by itself, identical twins that are raised separately from birth must be studied. Identical twins have a 100% genetic relationship, but if raised in separate environments, any similarity (beyond that expected by chance) in IQ must be due to similarity in genetics.

39. Bouchard et al. (1990) - Minnesota Twin Study  Conducted a longitudinal study since 1979, comparing MZA twins to MZT twins in terms of intelligence (MZA - monozygotic raised apart, MZT - monozygotic raised together)  Each twin completed approximately 50 hours of testing and interviews.  It was a cross cultural study, using participants from all over the world.

40. Bouchard et al. (1990) - Minnesota Twin Study  Results - concordance rates of intelligence from the study  Bouchard et al. concluded a heritability estimate of 70%  70% of intelligence can be attributed to genetic inheritance. 30% attributed to other factors. Same person87% MZA86% MZT76% DZT55% Siblings reared together 47%

41. Connecting Bouchard et al (1990) to question  This study relates to the effect of genetics on behaviour as the concordance rate between twins shows that their behaviour was affected mostly (70%) by genetics, rather than the environment, where the other 30% may be attributed to other factors in the surrounding environment.

42. Strengths Size of the study means it is more generalisable Nature of sample - cross cultural Mean age of participants 41 years, as opposed to previous studies with adolescents. Plenty of time for environmental factors to affect intelligence (i.e. participants will have completed education)Weaknesses  Relied on media coverage to recruit participants  Ethical concerns with the way twins were reunited  Frequency of contact between twins prior to study not controlled.  'Equal environment assumption' - twins reared together may not have experienced the same environment.

43.  Adoption Studies - investigating environment (no biological/genetic link between parents and child, so correlation in IQ is purely due to environment) Horn et al. (1979)  Conducted a study on parents who raised BOTH adopted and natural children.  All children have the same upbringing, therefore same environment, but some were similar in genetics and some were not.  Found no significant differences in correlation of parent-child IQs between natural and adopted children.  Adoptive parents were wealthy, white, middle class and children were poor, lower class backgrounds, with lower IQ parents.  Conclusion that genetics has little impact - mostly environment.

44. Niche Picking Hypothesis Scarr and McCartney (1983)  Horn et al (1979) findings could be explained by the “niche picking hypothesis” proposed by Scarr and McCartney (1983) ◦ Genes affect an individual’s preference for particular environments ◦ The environment then affects the development of the individual. ◦ Genetically similar people will tend to select similar environments, thus leading to similar IQ. ◦ It is possible that genetic predisposition influences individuals to tend towards environments that accentuate that disposition, thus leading to increased heritability throughout their lifespan. ◦ The niche picking hypothesis supports the influence of genetics on IQ.

45.  Genetics can influence intelligence as shown by supporting studies on influence of genetics.  Horn (1979) provided findings to suggest that the environmental factors influence intelligence more than genes ◦ Adopted children have a higher IQ correlation with the adoptive family, rather than biological family.  Genetic inheritance influences intelligence, and thus behaviour, to a great extent. ◦ large amount of supporting research ◦ the niche picking hypothesis refutes environmental factors and suggests genetic links to intelligence  Although it is important to note that the role of genetics in determining human behaviour and physical characteristics is significant, it is essential to bear in mind that although some characteristics are strongly affected by genetic inheritance, it is not a simple causal relationship, as other factors such as the environment can influence thus alter certain behaviour.