Twin and Adoption Studies

Question 1

what are twin and adoption studies used for ?

Answer 1

to investigate the effects of nature and nurture on behaviour

Question 2

what does nature refer to ?

Answer 2

refers to the biological causes for behaviour

Question 3

what is meant by ‘biological cause’ in nature ?

Answer 3

means the influence of genes that have been inherited from biological parents

Question 4

what does nurture refer to ?

Answer 4

the environmental causes of behaviour

Question 5

what is meant by ‘environmental cause’ in nurture ?

Answer 5

means the importance of upbringing, regardless of who the parents are

Question 6

what do twin studies investigate ?

Answer 6

the role of nature (genes)

Question 7

what do adoption studies investigate ?

Answer 7

the role of nurture (upbringing)

Question 8

what type of experiments are twin and adoption studies always and why ?

Answer 8

natural experiments because the independent variable being investigated (whether you are biologically related to your family or what type if twin you are) is a naturally occurring variable

Question 9

what do adoption studies look at ?

Answer 9

the impact of nurture on children who are raised by parents who are not their biological parents

Question 10

how are adoption studies made more valid ?

Answer 10

if the researchers have information about the child’s biological parent

Question 11

what does it mean if a child grows up with traits that resemble the adoptive parent more than the biological parent ?

Answer 11

this is stronger evidence that that these traits are due to nurture

Question 12

what are adoption studies usually measured with ?

Answer 12

usually measured using a correlational technique - the researchers are looking for a correlation between the behaviour of the children and their parents

Question 13

what is the interpretation to a correlation with adopted parent being higher than correlation with biological parent ?

Answer 13

behaviour is partly due to nurture (upbringing)

Question 14

what is the interpretation with adopted parent is lower than correlation with biological parent ?

Answer 14

behaviour is partly due to nature (genes)

Question 15

what are monozygotic twins ?

Answer 15

twins conceived from a single egg which later split - these twins share the same genes, this means they MUST be the same sex

Question 16

what are dizygotic twins ?

Answer 16

twins conceived when two or more eggs were fertilised at the same time - these twins share the same amount of genes as any other brother or sister (up to 50%)

Question 17

what is meant by identifying zygocity ?

Answer 17

deciding whether the twins are monozygotic or dizygotic

Question 18

what does it mean if MZ and DZ twins behave in the same way ?

Answer 18

nature has little to do with the behaviour

Question 19

what does it mean if MZ and DZ twins behave differently ?

Answer 19

suggests nature is at work - because the shared environment is nit producing the same behaviour so genetic differences could explain this

Question 20

what are twin studies measured with (statistic) ?

Answer 20

concordance rate

Question 21

what does concordance mean ?

Answer 21

“agreement” - if one twin shows a behaviour and the other twin does too, this is concordance

Question 22

what does 100% concordance mean ?

Answer 22

all the twins shared the behaviour in common (0% means none of them did)

Question 23

how is concordance rate used in twin studies ?

Answer 23

the concordance rate of the MZ twins is compared to that of the DZ twins

Question 24

what does it mean if MZ concordance is significantly higher than DZ concordance ?

Answer 24

behaviour partly due to nature

Question 25

what does it mean if MZ concordance is similar to DZ concordance ?

Answer 25

behaviour entirely due to nurture

Question 26

what does it mean if MZ concordance is 100%

Answer 26

behaviour entirely due to nature

Question 27

what does it mean if MZ concordance is significantly less than 100% ?

Answer 27

behaviour partly due to nurture

Question 28

what are two similarities of twin and adoption studies ?

Answer 28

1) adoption and twin studies are both natural experiments 2) both these methods focus on comparing people who share genetic material with people who share less genetic material while environment factors remain constant

Question 29

why are twin and adoption studies natural experiments ?

Answer 29

they study the influence of genetics and environment on behaviour - but they do this by observing naturally-occurring variables rather than manipulating IVs in a lab - this means they avoid a lot of ethical problems with manipulation humans in lab settings

Question 30

what are three differences between twin and adoption studies ?

Answer 30

1) twin studies are much better at studying the effects of nature (genes) 2) adoption studies are much better at studying the effects of nurture (upbringing) 3) adoption studies don't face the problem of assigning zygocity to twins, which can be unreliable

Question 31

why are twin studies better at studying the effects of nature ?

Answer 31

because MZ twins share 100% of their genes, whereas adopted children do not share 100% if their genes with either their biological parents - concordance rates between MZ twins tells us more than it does between children and their biological parents

Question 32

why are adoption studies better at studying the effects of nurture ?

Answer 32

we cannot be sure how little twins share the same environmental influences (Phenotype) - but we can be sure that adoptive parent provide almost all the upbringing of the adoptive children and that the biological parents contribute little to nothing

Question 33

what problem do twin studies avoid that adoption studies have ?

Answer 33

they don't have the problem of tracking down biological parents and persuading them to take part in the study - because of migration and ease of trace in the 21st century, this problem may be greater than it used to be

Question 34

what is a strength of twin studies ?

Answer 34

- they are a valid way of investigating the nature v nurture debate - MZ twins naturally share a genotype with their twin so the researchers are not manipulating this variable and so the risk of researcher bias is reduced - this also avoids ethical problems

Question 35

what is a weakness of twin studies ?

Answer 35

- difficult to generalise because they are rare - twins may have unusual lives that make them different to other children (e.g. they attract attention and often get treated the same way) - this may lead them to behave in a more similar way than normal siblings - this means that they might not be very representative pf other children and so they are less useful

Question 36

how might the results from twin studies be invalid ?

Answer 36

- it is hard to identify MZ twins without DNA tests - DZ twins can look similar and have the same blood group and similar fingerprints (commonly used tests) - if studies misidentify the zygocity of the twins then the studies become invalid and will lack credibility