Twins & Adoption Studies

1. What are identical twins?2. Why are they useful to study in Psychology?3. If Identical twins behave in similar ways and share

traits, what does this tell us about these behaviours?

4. However, might there be another reason as to why identical twins behave in similar ways or share traits?

5. Why are identical twins reared apart (adoption studies) useful to study?

Learning Objectives By the end of this lesson you:

• Must be able to describe (AO1) the Gottesman and Shields study.

• Must be able to describe (AO1) and evaluate (AO2) twin studies as a method in psychology.

Genes Shared

MZ Twins 100%

DZ Twins 50% (approx)

Siblings 50% (approx)

Adopted Children None

Concordance

Feature InterpretationMZ concordance issignificantly higher than DZconcordance

The disorder has a genetic component.

MZ concordance is same orsimilar to DZ concordance

The disorder is environmentally caused.

MZ concordance is 100% The disorder is genetically caused.

MZ concordance issignificantly less than 100%

The disorder has an environmental component.

Consolidation Task [twin studies]

1. Describe one research method used in the study of schizophrenia (6)

2. Evaluate one research method used in the study of schizophrenia (6)

A• Aim• What did they hope to find? What was their research question? What

theory is the study attempting to support? How is it going to support it?

P• Procedure• What did they do? How did they do it? Who did they do it to? When did

they do it?

R• Results• What did they find out? What data did they collect?

C• Conclusion • What does this mean? Did the results support the aim? Do the results

support the theory the study is based on?

Page 47-48

Aim(s)

To investigate the relative importance of genetic and environmental influences on schizophrenia by comparing MZ and DZ twins.• 1.Wanted to know the extent to which

Schizophrenia was genetic• 2.Wanted to replicate other studies that had

found a genetic link with schizophrenia

Procedure

Collected secondary data from hospital records of twins from the Maudsley and Bethlem Royal Joint Hospital as well as collecting primary data by interviewing and giving personality (psychometric) tests. From a sample of 392 patients 57 twin pairs were selected aged between 19 –64yrs (average age 37) where at least one of the twins were on the register of the hospital as suffering from schizophrenia (5 pairs were both on the register).

ParticipantsMZ DZ (same sex) Total

Male 13 17 30Female 11 16 27

Total 24 33 57

The following information was obtained:

• Case histories based on a self-report questionnaire and interview with the twins and their parents to provide a record of verbal behaviour

• A personality test• A test used to measure disordered thinking conducted on twins and

parents.

Results

Analysis of the data has looked for similarities between each patient and their twin. Concordance was assessed in three different ways:• Grade 1: both the patient and

co-twin had been hospitalised and diagnosed with schizophrenia.

• Grade 2: both patient and co-twin have had psychiatric hospitalisation but the co-twin has a different diagnosis.

Grade MZ (%) DZ (%) 1 42 92 12 93 25 27

Normal 21 55

• Grade 3: The co-twin has some psychiatric abnormality (e.g. out-patient care, GP care, neurotic or psychotic personality profile or being abnormal on interview)

ConclusionsNATURE• Genes appear to play an

important role in schizophrenia because the concordance rate is higher in MZ twins than DZ twins. (MZ twins are at least 48 times more likely to have schizophrenia than someone in the general population)

• There is some evidence to suggest that there is a set of genes responsible but not one in particular.

NURTURE• Environmental factors must also

be important. The Diathesis-stress model suggests that individuals have a genetic predisposition for schizophrenia which is in part triggered from the environment.

• Gottesman (1991) went on to investigate the influence of genes on by combining the results of 40 investigations spanning over 60 years. Concordance rate for schizophrenia was 48% for MZ and 17% for DZ twins.

Twin sisters Zara and Elizabeth shared everything as they were growing up, dolls, secrets, boyfriends. Recently, Zara has been diagnosed with schizophrenia and now Elizabeth is terrified that she’ll be next. Use psychological concepts, theory and studies to discuss whether Elizabeth is right to be worried.(8)

Tip: your answer must include an evidence based argument that Elizabeth should be worried but also a counter-argument, presenting reasons why Elizabeth may be okay, thoughts about how Elizabeth could protect herself further, evidence which refuters the role of genetics in schizophrenia, possibly drawing upon theories which suggest schizophrenia is caused by environmental experiences, limitations of studies which support the genetic base of schizophrenia

• Must be able to describe (AO1) the Gottesman and Shields study.

• Must be able to describe (AO1) and evaluate (AO2) twin studies as a method in psychology.

Complete the worksheet

Learning Objectives By the end of this lesson you:

• Must be able to evaluate (AO2) the Gottesman and Shields study.

• Must be able to describe (AO1) and evaluate (AO2) twin studies as a method in psychology.

Strength Weakness

Conversion Task (from Venn)

Evaluate the Gottesman and Shields study [8]

20 minutes

• Must be able to evaluate (AO2) the Gottesman and Shields study.

• Must be able to describe (AO1) and evaluate (AO2) twin studies as a method in psychology.

www.jamiesflipped.co.uk@jamiesflipped