Biologicalš§ ā¢ Brendgen's Study (2005) Flashcards
What is a zygote?
A fertilised egg cell
What is the scientific name for non-identical twins?
Dizygotic
What percentage of shared DNA do non-identical twins share?
50% shared DNA
What is the scientific name for Identical Twins?
Monozygotic
What percentage of shared DNA do identical twins share?
100% shared DNA
List 4 environmental factors that can attriubte for similar behaviour in any set of twins
- Same parents
- same age
- same school
- same home/neighbourhood
Overall: Almost identical upbrining (minus personal experiences)
What does āNatureā argue aggression is due to?
Biological causes/ genes
What does āNurtureā argue aggression is due to?
Environmental/ societal factors
What are the 2 main components of social aggression?
- Indirect aggression
- Relational aggression
What is indirect aggression?
Verbal/ non physical aggression e.g. spreading gossip
What is relational aggression?
Still non physical, but more hurtful that indirect e.g. breaking off a friendship, pulling faces, false rumours e.g. ābitchinessā
What is a persons genotype?
Your genetic makeup e.g. MZ: 100% Genotype similarity
DZ: 50% Genotype similarity
What is a persons phenotype?
Combination of a personsā genes and their envirionment & that impact on them as an idividual e.g A set of twinsā phenotype could be similar but each twin will have their own experiences with their environment so wont have the same level of similarity in phenotypes like in genotypes
What was the year Brendgenās study was published?
2005
What is the sample of Brendgenās study?
234 Pairs of MZ & DZ 6 Year-old Twins
How many people were included in the sample overall?
468
Complete this table on the numbers of different types of twins included in Brendgenās study
How did Brendgen aquire her sample of twins?
The sample of twins was aquired via the Quebec Newborn Twins Study
What type of study was the Quebec Newborn Twins Study (QNTS)?
Longitudinal Study ( A study where researchers repeatedly observe the same variables over contiuned periods of time) (Brendgen took data when twins were 6)
In the QNTS how was the zygocy of the twins determined (Describe both times)?
- Initially they were assigned based on Phsyical resemblence which was subjective and not reliable
- To ensure zygocy was correct 123 pairs were DNA tested to check assignment
What was the result of the DNA testing on the QNTS?
- 123 Pairs of twins were tested
- was found that 94% of twins were correctly assigned zygocy
What was concluded after the DNA testing about the reliability of the zygocy of the twins?
Was determined that 94% was āreliable enoughā and therefore the issue/ fault with zygocy was mitigated and was no longer a flaw
What type of sample was the one included in Brendgenās study?
A clutster sample
What is a cluster sample?
A sample aquired from an existing study
What is sampe attrition?
When participants drop out of studies
What was the cause of sample attrition in the QNTS?
By the time the twins had reached 6 years old there was only 234 pairs remaining (the pairs used by Brendgen) as 88 pairs had dropped out of the study
What does the sample attrition in the QNTS suggest about the sample of Brendgenās study
The dropping out of participants to leave 234 pairs may have made the selection of twins less representative of all socioeconmic backgrouds as cost of loving could have been the reason behind leaving the study - therefore sample unable to be gen etcā¦
What is the Aim of Brendgenās study?
To find out if there is a difference between phyiscal and social aggression in 6-year school children & if there is a link between such forms of aggression and nature & nurture (biology/genes or environmental factors) with MZ & DZ twins
What was the procedure of Brendgenās study?
- Teachers were asked to rate each child on 6 statements, respondng to each satement with one of the elements from a 3 point scale
- Children were given easier task, they were shown a pictures of the classmates/ twins and was asked to circle 3 people who best fit **4 statements **
- Statements were 50-50 split between social and phyiscial aggression for both types of interviews
What were the 3 elements on the 3 point scale that the teachers had to use?
0 - never
1 - sometimes
2 - often
IMPORTANTLY IT STARTS AT 0 AND ENDS AT 2, NOT 1-3
Why was having children and teachers give opinions a strength for the study?
Because it created inter-rater reliability, by having multiple sources the creditability of results can increase and so can validity
Give 2 examples of questions from the Peer questionnaire, one social, one physical
- PHSYICAL: āGets into fightsā
- SOCIAL: āTells mean secrets about another childā
Give 2 examples of questions from the Teacher questionnaire, one social, one physical
- PHSYICAL: āPhysically attacks othersā (Similar to Peer ->) āGets into fightsā
- SOCIAL: āSays bad things or spreads nasty rumours about another childā (Similar to Peer ->) āTells mean secrets about another childā
Why was having the set questions for the peers and teachers a strength for the study?
As it meant the procedure was standardised and therefore replicable
What were the results of Brendgenās study?
- Teachers rated boys more physically aggressive & girls more socially aggressive
- Concordance - 0.79 CORRELATION in MZ twins in terms of physical aggression e.g. if one twin was aggressive then the other was also likely to be aggressive - MZ twins had strikingly similar behaviour, whether it was aggressive or non-aggressive. (SUPORTS BIO - insinuating physical agg. linked to genes)
- The MZ twinsā correlations for social aggression were similar to the DZ twinsā correlations e.g social aggression is less linked to genetics, because both types of twins seemed to be equally affected by their surroundings, unlike with physical aggression
What did Brendgen conclude from her study?
- 50-60% of Physical Aggression can be linked to genetics/ nature as it was shared more by MZ twins (100% DNA) than DZ twins (only 50% DNA)
- Genes only seem to account for 20% of Social Aggression
- Non-shared environment has influence shown by other 40% of Physical aggression and 60% of social aggression being due to it (Inferring nurture can be linked with social aggression as largest %)
- Infers remaining 20% of social aggression is due to shared environments e.g. parenting/ home life
What is the Generalisability of Brendgenās study?
- Representative as it has a large sample of 234 pairs of twins
- Although may not be entirely representative as although it is represenative of 6 year old MZ & DZ twins it may not be for older twins or children who arent twins
- Sample attrition perhaps leading to less diverse sample and a higher average socioeconmic status so not representative
What is the Reliability of Brendgenās study?
- Reliability due to question standardisation
- Internal reliability due to questions being accuratley on topic (aggression)
- Inter-rater reliability with teacher and peer rated
- Zygocy of children being backed-up by 94% accuracy via DNA test
What is the Application of Brendgenās study?
- Educating parents & children e.g. PSHE & early intervention to specifically combat social aggression as Brendgen has shown its link to nurture/ envrionmental factors/ shared environments such as home
What is the Validity of Brendgenās study?
- All twins have unique expereiences e.g. although same parents one may be favoured therefore cant 100% ensure controlled environment therfore high ecological validy as reflective of mundane environments
- Correlation only shows a relationship between variables, doesnt show why, no causation
- CLEAR STRENGTH = Study avoids being reductionist as it thoroughly takes into consideration genetic AND environmental factors throughout experiment
* Low population validty due to sample attrition
What were the Ethics of Brendgenās study?
- POSITIVE POINT Got presumptuive consent from twinsā parents and school (Although twins were underage regardless of presumptuive consent)
- NEGATIVE POINT social harmony may be impacted as the peers were essentially labelling other children (their friends) as mean/ aggressive. This could easily disrupt friendships as some children could have gotten upset and their self-esteem may have been damaged knowing their friends have been labelling them as aggressive - therefore inducing Pyschological harm
