MZ/DZ Twin Studies

You need to be able to describe, apply/explain and evaluate the use of twin studies. These came up in Biological Psychology and also they were helpful in evaluating biological explanations of schizophrenia and uni-polar depression. This area focuses on MZ/DZ twin studies but psychologist also do studies on “twin raised apart”.

Twin Studies

The following documents all need reviewing for suitability for new spec, currently unchanged from 2008, the content will be unchanged on the whole but the mark schemes etc refer to old spec.

describe-one-research-method-used-to-investigate-schizophrenia: very useful PowerPoint to describe this important research method.

gottesman-and-shields-1966 : A PowerPoint about this famous study which helps explores the heritability of schizophrenia.

gottesman-and-shields: A Handout about this famous study.

learning-obs-for-twin-studies-schizophrenia: Learning objective relating to twin studies and Gottesman and Shields; examiner reports and mark schemes relate to old spec but still useful.

test-on-g-and-s: Questions to check your understanding of this study.

twin-studies-and-schiz: Handout about the research method of twin studies including important evaluation points.


Practice Questions

  1. Researchers often compare the concordance rates of monozygotic (MZ) and dizygotic (DZ) twins raised apart to see if a characteristic can be explained by nature or nurture. If the concordance rate for a characteristic is higher for monozygotic twins than for dizygotic twins it means it is probably due to

A the environment

B genetics

C both the environment and genetics

D neither the environment nor genetics