Session 18

two Examine one interaction between cognition and physiology in terms of behaviour. Evaluate two relevant studies.

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

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

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

What exactly is a gene?? Watch the ‘What is a gene video?’

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

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) 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

 If a correlation is found it is called the concordance rate

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

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

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

Comparing Monozygotic twins (MZ) with Dyzygotic 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?

 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 preferrable 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.

 Prospective studies identify traits that are considered to be inherited. Those who are considered “genetically vulnerable” are then followed over many years to see if they actually manifest the behaviour. This is used, for example, in the study of schizophrenia.  There is an ethical concern in such research that it may cause undue stress and lead to iatrogenic effects in those who are labeled as vulnerable.

 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

 Read through the article: Genetics and human behaviour: the ethical context  Take notes You could incorporate this into a response for the question: “Discuss ethical considerations related to research studies at the biological level of analysis”

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

 Is intelligence constructed by Nature or Nurture?  How does one’s biology effect intelligence?  How does one’s environment effect intelligence?

 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