Biological🧠 • Brendgen's Study (2005)

Question 1

What is a zygote?

Answer 1

A fertilised egg cell

Question 2

What is the scientific name for non-identical twins?

Answer 2

Dizygotic

Question 3

What percentage of shared DNA do non-identical twins share?

Answer 3

50% shared DNA

Question 4

What is the scientific name for Identical Twins?

Answer 4

Monozygotic

Question 5

What percentage of shared DNA do identical twins share?

Answer 5

100% shared DNA

Question 6

List 4 environmental factors that can attriubte for similar behaviour in any set of twins

Answer 6

• Same parents
• same age
• same school
• same home/neighbourhood
  Overall: Almost identical upbrining (minus personal experiences)

Question 7

What does ‘Nature’ argue aggression is due to?

Answer 7

Biological causes/ genes

Question 8

What does ‘Nurture’ argue aggression is due to?

Answer 8

Environmental/ societal factors

Question 9

What are the 2 main components of social aggression?

Answer 9

• Indirect aggression
• Relational aggression

Question 10

What is indirect aggression?

Answer 10

Verbal/ non physical aggression e.g. spreading gossip

Question 11

What is relational aggression?

Answer 11

Still non physical, but more hurtful that indirect e.g. breaking off a friendship, pulling faces, false rumours e.g. ‘bitchiness’

Question 12

What is a persons genotype?

Answer 12

Your genetic makeup e.g. MZ: 100% Genotype similarity
DZ: 50% Genotype similarity

Question 13

What is a persons phenotype?

Answer 13

Combination of a persons’ genes and their envirionment & that impact on them as an idividual e.g A set of twins’ 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

Question 14

What was the year Brendgen’s study was published?

Answer 14

2005

Question 15

What is the sample of Brendgen’s study?

Answer 15

234 Pairs of MZ & DZ 6 Year-old Twins

Question 16

How many people were included in the sample overall?

Answer 16

468

Question 17

Complete this table on the numbers of different types of twins included in Brendgen’s study

Answer 17

Question 18

How did Brendgen aquire her sample of twins?

Answer 18

The sample of twins was aquired via the Quebec Newborn Twins Study

Question 19

What type of study was the Quebec Newborn Twins Study (QNTS)?

Answer 19

Longitudinal Study ( A study where researchers repeatedly observe the same variables over contiuned periods of time) (Brendgen took data when twins were 6)

Question 20

In the QNTS how was the zygocy of the twins determined (Describe both times)?

Answer 20

• 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

Question 21

What was the result of the DNA testing on the QNTS?

Answer 21

• 123 Pairs of twins were tested
• was found that 94% of twins were correctly assigned zygocy

Question 22

What was concluded after the DNA testing about the reliability of the zygocy of the twins?

Answer 22

Was determined that 94% was ‘reliable enough’ and therefore the issue/ fault with zygocy was mitigated and was no longer a flaw

Question 23

What type of sample was the one included in Brendgen’s study?

Answer 23

A clutster sample

Question 24

What is a cluster sample?

Answer 24

A sample aquired from an existing study

Question 25

What is sampe attrition?

Answer 25

When participants drop out of studies

Question 26

What was the cause of sample attrition in the QNTS?

Answer 26

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

Question 27

What does the sample attrition in the QNTS suggest about the sample of Brendgen's study

Answer 27

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 etc...

Question 28

What is the Aim of Brendgen's study?

Answer 28

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

Question 29

What was the procedure of Brendgen's study?

Answer 29

* 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

Question 30

What were the 3 elements on the 3 point scale that the teachers had to use?

Answer 30

**0** - never **1** - sometimes **2** - often IMPORTANTLY IT STARTS AT 0 AND ENDS AT 2, NOT 1-3

Question 31

Why was having children and teachers give opinions a strength for the study?

Answer 31

Because it created *inter-rater reliability*, by having multiple sources the creditability of results can increase and so can validity

Question 32

Give 2 examples of questions from the Peer questionnaire, one social, one physical

Answer 32

* **PHSYICAL**: 'Gets into fights' * **SOCIAL**: 'Tells mean secrets about another child'

Question 33

Give 2 examples of questions from the Teacher questionnaire, one social, one physical

Answer 33

* **PHSYICAL**: '**Physically attacks others**' (Similar to Peer ->) 'Gets into fights' * **SOCIAL**: '**Says bad things or spreads nasty rumours about another child**' (Similar to Peer ->) 'Tells mean secrets about another child'

Question 34

Why was having the set questions for the peers and teachers a strength for the study?

Answer 34

As it meant the procedure was standardised and therefore replicable

Question 35

What were the results of Brendgen's study?

Answer 35

* 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 twins' correlations for social aggression were similar to the DZ twins' 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

Question 36

What did Brendgen conclude from her study?

Answer 36

* **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

Question 37

What is the ***G**eneralisability* of Brendgen's study?

Answer 37

* 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

Question 38

What is the ***R**eliability* of Brendgen's study?

Answer 38

* 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

Question 39

What is the ***A**pplication* of Brendgen's study?

Answer 39

* 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

Question 40

What is the ***V**alidity* of Brendgen's study?

Answer 40

* 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**

Question 41

What were the ***E**thics* of Brendgen's study?

Answer 41

* **POSITIVE POINT** Got *presumptuive* consent from twins' 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**