The Roles of Genes on Behaviour and Twin/Adoption Studies

Frage	Antworten
What are Genes?	Genes are in our DNA and they are responsible for protein synthesis which influences our development.
What is the genome?	The genome is all of the genes in a cell. It's believed that the human genome has around 3 billion base pairs and 20,000-25,000 genes.
What are chromosomes?	Chromosomes are what carry our DNA. We have 46 in each cell- 23 chromosomes from our father and 23 from our mother.
How do genes work?	You will get one variation of a gene (allele) from your mother and one from your father. One of these genes will be more dominant and come out in the offspring. For example, a mother has brown eyes and a father has green. The offspring is very likely to have brown eyes. The weak gene is known as the recessive gene.
Example of chromosomes?	The chromosomes that make someone biologically female are known as the XX chromosomes. Males will have XY chromosomes. This chromosome alone distinguishes whether you will develop male or female organs.
What is the nature side of the nature/nurture argument?	Nature argues that the characteristics of a person come through due to biological influences such as genes inherited from parents.
What is the nurture side of the nature/nurture argument?	Nurture refers to the upbringing of a person having more of an effect on their development than their biological inheritance.
What are Monozygotic twins (MZ twins)?	Monozygotic twins share 100% the same genes. They came from the same zygote. They're identical.
What are Dyzygotic twins (DZ twins)?	Twins that only share 50% the same genes. They came from two zygotes. They aren't identical.
Evaluation for Twin Studies:	Good reliability as 100% of genes shared so one gene will always be in the other twin too, good reliability due to large volume of data produced but bad as we can't tell if nature or nurture caused something (not all the time).
Separated Twins	Another way to test the effects of genes are to study MZ twins who were separated at birth. If those who have grown up together are more alike than those who grew up apart, it's more likely that nurture has a bigger effect on character.
Aim of Brendgen (2005)	Mara Brendgen and her colleagues were interested in social aggression in twins. They wanted to study whether social aggression was caused by genes or the environment whilst also looking at the same cause for physical aggression and to test a connection between the two types of aggression.
Who were the participants of Brendgen 2005?	Participants recruited from the Quebec Newborn Twin Study. 322 pairs of twins tested but complete data was only recorded for 234 pairs. Of these, 44 were MZ males, 50 were MZ females, 41 DZ males, 32 DZ females, 67 mixed sex DZ twins.
Procedure of Brendgen 2005?	Longitudinal data gathered at 5, 18, 30, 48 and 60 months, then again at 6 years. The data was a behaviour rating from both teachers and classmates on the aggression of the twins in question. Teachers were asked to fill out scale-based questions, classmates were asked to pick out pictures of classmates who fit the socially aggressive statements provided.
Results of Brendgen 2005?	Higher correlation in psychical aggression in MZ twins than DZ twins. Social aggression was similarly correlated with MZ twins and DZ twins. Physical aggression may be influenced more by genes and social aggression more by environment.
Generalisability of Brendgen et al?	Good, lots of different twin types and all different genders. All gathered from same place so unsure of culture differences.
Reliability of Brendgen 2005?	Lots of participants so good reliability as statistical tests can be done. Procedure is standardised so repeatable and longitudinal procedure meant it was reliable over a length of time.
Applications of Brendgen 2005?	Helps us to understand classroom aggression and its causes. Also helped us to learn whether certain traits are inherited or obtained due to our enviroment
Validity of Brendgen 2005?	Was in child's natural environment so high in ecological validity and external validity. High in mundane realism. Low in internal validity as couldn't control all extraneous variables.
Ethics of Bredgen 2005?	There was no deception and presumed there was full consent as all of the twins who participated were members of the QNTS.
Why are adoption studies helpful in psychology?	The environment adopted children grow up in is not the same environment as their biological family so it's clear to distinguish between genes and environment.
Aim of Heston 1966?	There was evidence from twin studies that schizophrenia was particularly due to genes so Heston wished to do an adoption study to check this.
Participants of Heston 1966?	50 children who had been adopted who had schizophrenic biological mothers. All mothers were in an Oregon State psychiatric hospital. The 50 children had matched pairs of another 50 children who had mentally fit mothers. Matched on sex, type of placement and length of time in child care.
Procedure of Heston 1966?	When the children who had schizophrenic mothers but were adopted were older, they were interviewed to see if any of them had gone on to develop schizophrenia themselves. All interviews were in the subjects homes. Information evaluated blindly by other psychologists.
Findings of Heston 1966?	Previous research had suggested the rate of developing schizophrenia if a parents was schizophrenic was 10%. Of all 47 adults interviewed, 5 of them had been hospitalised with schizophrenia. This supported the 10% finding.
Generalisabilty of Heston 1966?	Quite a large sample of participants being as the requirements were so precise. There was a variation of 30 years between some of the ages of participants but all of their mothers had been hospitalised in Oregon for Schizophrenia.
Reliablity of Heston 1966?	Lots of forms of data used in collection (questionnaires, interviews, observations, medical records), standardised procedure, structured interview. Overall, good reliability.
Applications of Heston 1966?	Understanding and treating schizophrenia and giving special care to those more likely to develop it.
Validity of Heston 1966?	No demand characteristics as it was in the participants own homes, high ecological validity, believed the interview was a medical checkup so even fewer demand characteristics, but low internal validity as lack of control over extraneous variables.
Ethics of Heston 1966?	Deception on the interviews being as the participants believed they were just having a normal medical checkup interview.

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