The key answer of exercise 6

Two other variables that may affect studies into the relationship between gaming and bad behaviour:

• level of education, class or income
• amount of hours played

Two examples of causal links that have been conclusively proved:

• smoking and cancer
• poverty and (ill)health
• education and economic performance

Two things that have not yet been proved because of conflicting evidence:

• fat and heart disease
• prison sentences and crime