1. Genetics and Behavior
With reference to relevant research studies, to what extent does genetic inheritance influence behavior?

2. Genotype
Genes are responsible for physical and behavioral characteristics
23 pairs of chromosomes in every human cell
Except egg and sperm
Combine to make the human genome
But is it genetics alone?
NOT a simple causal relationship

3. Phenotype Environmental factors impact development
Diet and habitat
Interaction of genotype and environment is called the phenotype
1st seen in plants
Media often makes exaggerated and reductionist claims

4. What does genetic information do?
Helps us understand human behavior
Examples:
PKU (mostly physical)
Schizophrenia
Twin research

5. Phenylketonuria (PKU)
Definition:
Inherited disorder
Enzyme deficiency
Accumulation of phenylalanine that causes brain damage
Behavior change
Prenatal tests
Restrict artificial sweeteners

6. Heston, 1966
Schizophrenia: Mental disorder that causes hallucinations, delusions and sever disorganization of thought
Method: correlational
Hypothesis: physical and behavioral similarities observed between parent and child are largely caused by genetics
Schizophrenia has a genetic component

7. Procedure (adoption studies)
Children is foster homes that had a mother with schizophrenia and those that didn’t
Results
General population 1% schizophrenia
Mothers with schizophrenia  10%
Strong evidence that there is a genetic link
Implications
Nature impacts schizophrenia
What about nurture?
If they were placed in a nurturing environment the rates of schizophrenia should decrease

8. Bailey and Pillard, 1991 Behavior: Homosexuality
Method: Twin  Correlational
Results (concordance)
Monozygotic twins  52%
Dizygotic twins  22%
Implications:
Must be a genetic component but not the only component

9. Santtila et al 2008 Criticisms of Bailey and Pillard, 1991
Too narrow of a definition of homosexuality
Distinguish between overt and covert behavior
Method: correlation twin research using surveys
Procedure
Homosexual activity and potential for homosexual activity
Twins and siblings (both genders)
Results: MZT were twice as likely to answer the questions in the same way

10. Take notes on the “Genetic Leash”
Bouchard Research
Extra Credit
Take notes on the “Genetic Leash”

11. Depression Mood Disorder Diagnostic criteria (symptoms)
Insomnia or hypersomnia
Loss of pleasure is everyday activities
Feelings of worthlessness
Loss of interest and motivation
Persist longer than two months

12. Depression and 5-HTT Gene

13. Caspi et al, 2003
Behavior: Depression after stressful event and the 5-HTT gene
Serotonin is neurotransmitter linked to depression
Method: Correlational
Relationship between mutated 5-HTT gene, amount of stressful events and depression
Hypothesis: 5-HTT gene influences the level of serotonin and makes an individual more likely to experience depression
Procedure: genetic testing and surveys
Results: those with mutated gene more likely to experience depression after stressful events
Gene moderates response to depression
Similar to PTSD?

14. Implications: Evaluation
Relationship between gene mutation an depression
Evaluation
People who did not carry the mutated gene also experience depression
43% population has mutated 5-HTT gene
Not possible to show cause and effect
Could it be the stressful events that made people depressed

15. Twin Research MZ  Identical Twins DZ  fraternal twins
Same egg, share 100% genes
DZ  fraternal twins
Different eggs, share 50% genes
Sibling born at the same time
Concordance rate
Likelihood or probability that if one has the trait the other will also have it
To what extent is a trait inherited
Intelligence, homosexuality, PKU, depression

16. What does twin research look like?
One twin acts like a control
MZ compared to DZ
MZ reared together compared to reared apart
Shows power of the environment
High concordance rate for MZ compared to DZ indicated the trait or disease is linked to genes
Differences in MZ are attributed to environment

18. Bouchard et al, 1990 Behavior: MZ together and MZ apart
Intelligence
Hypothesis: whether reared apart or together, MZ will have a high rate of concordance
Method: correlational
Procedure: WAIS IQ test of MZA and MZT
Results: Concordance rate was 69% for MZA and 88% for MZT
Implications:
70% of intelligence is based on genetics
In a white, middle-class, industrialized nation

19. Evaluation
IQ can be increased, but the increase is based on environment
Not cause and effect
Concordance rate was not 100% but still high
No control for environmental factors
The environments were most likely very similar
Who adopts babies?
Selective placement
Self-selected sample does not allow for full generalization

20. Problems with genetic research
Cannot clearly determine to what extent genetic inheritance influences behavior
Concordance rate is not cause and effect
Knowledge about genes is still limited
DZ twins may not be treated the same way
Boy and girl
Cute and ugly

21. Writing an FRQ
With reference to relevant research studies, to what extent does genetic inheritance influence behavior?
Introduction
Introduces the theory and research that will be discussed in the essay
Summary of theory (explanation of behavior)
The BIG Four
Culture, Gender, ethics, methodology
2-3 research summaries
Researcher, aim/hypothesis, method, short procedure, results, implications (link to the theory)
Evaluation of theory and research
Contradicting/supporting research
contradicting/supporting theory