Session 6 Genetic Influence on Behaviour

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

 What are the principles of the biological level of analysis?

1. There are biological correlates of behaviour 2. Animal research can provide insight into behaviour 3. Human behaviour is, to some extent, genetically based

With reference to relevant research studies, to what extent does genetic inheritance influence behaviour?

to what extent With reference to relevant research studies, to what extent does genetic inheritance influence behaviour? What the command term means: Consider the merits or otherwise of an argument or concept. Opinions and conclusions should be presented clearly and supported with appropriate evidence and sound argument.

What are genes? Is behaviour to some extent predetermined by our genes? How can we study this? What other factors may be important?

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

What exactly is a gene??

 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

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

 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

 Researchers often use correlational research to investigate genetic inheritance of behaviours  They calculate a concordance rate: correlation between family members  If a behaviour has a genetic influence on behaviour then we would expect to see a higher concordance rate between family members who share more DNA  Several research methods can be used, these include: ◦ Twin Studies ◦ Family Studies ◦ Adoption Studies LIMITATION: As there is no manipulation of variables a cause and effect relationship can not be established

1. Monozygotic (MZ) ◦ Fertilized from one egg that splits in two  Identical (share 100% of their genes) 2. Dzygotic (DZ) ◦ Fertilized from two eggs  Brothers and sisters (share 50% of their genes)

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? Video: THE STUDY OF TWINS

 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.

 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.

 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 preferable to twin studies?

 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.

 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.

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

 What is it?  Is intelligence influenced by genetic inheritance or the environment?  How is it measured?

1. Do you think that these tests appropriately evaluate your intelligence? 2. Do you feel that the tests were adequate? Why or why not? 3. How would you change the tests to make them reflect more accurately what you consider to be your intelligence?

 Often defined as the general mental ability to learn and apply knowledge to manipulate your environment, as well as the ability to reason and have abstract thought.

 Intelligence is an aspect of behaviour that has been studied in relation to genetics  Charles Spearman ◦ early intelligence theorist ◦ found students performance across different subjects was positively correlated  Alfred Binet ◦ Developed Intelligence Quotient tests to measure intelligence ◦ There are other measures but this is most widely accepted method is by measuring a person’s intelligence ◦ Based on a series of tests which assess various types of abilities such a mathematical, spatial, verbal, logic and memory. ◦ The results from such tests done on a group that is representative of the wider popular shows the classic ‘bell-shape’ distribution, meaning that most people are of average intelligence with a few at the extreme ends of the scale.

 Ulric Neisser - article in The American Scientist (1997)- average mean scores on IQ tests are increasing by about 3 points every 10 years  Why might this be?

 Ulric Neisser - article in The American Scientist (1997)- average mean scores on IQ tests are increasing by about 3 points every 10 years  Why might this be? - higher increase in abstract-reasoning ability - cause: unknown... possibly: - real increase in intelligence - increasing ability to crack intelligence tests - better nutrition - improved schooling - different child-rearing practices - increased use of technology in modern life  Neisser : living in a highly visual environment may play an important role in the rise of IQ scores.

siblings  Conducted a meta-analysis of 111 studies of siblings from intelligence research from around the world  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. Meta-analysis: the statistical synthesis of the data from a set of comparable studies of a problem that yields a quantitative summary of a pooled result.

 Large cross cultural sample= 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.

 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.

 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 person tested twice 87% MZA86% MZT76% DZT55% Siblings reared together 47%

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. not  'Equal environment assumption' - twins reared together may not have experienced the same environment.

 Conducted a study on parents who raised BOTH adopted and natural children.  All children have the same upbringing, therefore same environment but only biological children share genes with parents  Found no significant differences in correlation of parent-child IQs between natural and adopted children.  Adoptive parents were wealthy, white, middle class with high IQ and children were poor, lower class backgrounds, with lower IQ parents.  Horn’s conclusion = genetics has little impact - mostly environment.

 Conducted well-controlled adoption studies in France  Findings: transferring an infant from a low socio- economic status family to a home with high socio- economic status parents improves childhood IQ by points  What does this suggest?

 Socio-economic class appears to be an important environmental factor in developing intelligence.  They suggest: “Poverty - not genetic inferiority – is key to understanding the differences in intelligence.”

 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 but also acknowledges enviromental factors

1. How do we define intelligence – and why does it matter? 2. To what extent is intelligence biological? (what are the strengths and limitations of a purely biological argument?) 3. Can intelligence change over time? What are the implications for schools if we find that intelligence has a biological basis and cannot be changed?

Conclusion: refer to WHAT EXTENT genes influence not just what they influence Evidence of Environmental Factors Evaluation of evidence 2- link back to question Evidence of Genetic Inheritance Evaluation points for evidence 1- link back to question 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?