Kaij’s Twin Study of Alcohol Abuse

• What was the aim of Kaij's twin study on alcohol abuse?

  To see if alcoholism is hereditary
• How do twin studies assess the contributions of nature and nurture?

  By comparing nature (genetic) and nurtural (environmental) influences
• What type of twins were identified in Kaij's study?

  MZ (Monozygotic) and DZ (Dizygotic)
• How many MZ twins were identified in the study?

  48
• How many DZ twins were identified in the study?

  126
• What percentage of MZ twins were both alcoholic?

  61%
• What percentage of DZ twins were both alcoholic?

  39%
• What does it suggest if MZ twins have a higher alcoholism rate than DZ twins?

  Genetic vulnerability plays a role in alcoholism
• What would we expect if alcoholism was entirely genetic?

  All MZ twins would be alcoholics
• What would we expect if alcoholism was entirely due to environment?

  No difference between MZ and DZ twins
• What is one weakness of Kaij's twin study?

  Flaws in the study design
• Flawed study: Why does the temperance board data lack validity?

  It only includes publicly displayed alcohol abuse. As well as this, the data collected was self-report.
• What is a strength regarding supporting research?

  Kendler et al conducted a study which found that MZ twins are more likely to be alcoholics
• What do Prescott et al. suggest about hereditary factors and alcoholism?


  For both males and females, genetic factors have major influence on alcoholism.
• What is a weakness, and common misunderstanding about genetic vulnerability in addiction?

  People think addiction is inevitable if inherited
• Why is it important to understand the implications of genetic research?

  Both nature and nurture are important factors
• What was the sample population in Kaij's twin study?

  Male twins from Sweden
• Who was interviewed to collect information about drinking habits?

  Twins and their close relatives
• What does the overrepresentation of twins with social problems suggest?

  Social issues may correlate with alcohol abuse
• What is the implication of the study's conclusions regarding genetic vulnerability?

  Genetic factors influence alcohol abuse risk
• What does monozygotic mean?

  Derived from a single ovum, and therefore identical.
• What does dizygotic mean?

  Derived from two separate ova, and therefore not identical.
• How many male twins were identified where at least one twin was registered with the Swedish temperance board?

  310
• What was the total number of twin participants?

  384
• What is the full name of the researcher and what year was the study conducted?

  Lennart Kaij conducted the study in 1960