Lesson Idea: Thinking critically about correlations

Travis DixonResearch Methodology

Understanding that correlation does not mean causation is an important outcome in IB Psychology.

When looking at correlational studies and quasi-experiments it’s important, I think, to allow students to make the obvious conclusion first, which is generally one of causation. But a big part of the IB Psychology course is helping them to understand the mantra: correlation does not mean causation. 

This activity idea works well as a follow-up to the other activity about causation versus. correlation.

I’ve found the following activity to be a great one for introducing the importance of critical thinking about studies as well as giving students some practice at it. As all my favourites, it takes minimal prep and has maximum effect.

In my workbook I have the following correlational summaries from studies for students to read and discuss in small groups. Their task is to come up with two conclusions from each of the correlational results. The first conclusion will probably be causational, but then they need to think more deeply about the results and offer an alternative-explanation. They might offer an example of bidirectional ambiguity, or they could come up with an alternative variable that might explain the relationship. I give them ten minutes and then we discuss as a class.


Fast finishers can be extended by identifying if the studies are examples of positive or negative correlations.

The Studies

Brain injury and aggression (EXAMPLE)

One study found that soldiers from the Vietnam War who had injury to the front part of their brains (the frontal lobe) were more aggressive than war veterans who didn’t have an injury to that part of the brain.

  • Explanation 1: maybe damage to the frontal lobe makes people aggressive.
  • Explanation 2: perhaps more aggressive soldiers were more likely to experience a head injury in battle (because they were more willing to be confrontational).

Violent TV and Crime 

Studies have shown that the more violent TV a child watches when they’re younger, the more likely they are to commit a crime when they’re adults. (More info).

TV and Attention

For every one hour on average that a three year old watches, they are 10% more likely to have attentional problems when they’re aged seven. So a three year old child that watches four hours of TV on average, is 40% more likely to have attentional problems than a three year old child that watches one. (More info – Also see page 424 of IB Psychology: A Student’s Guide for TV and attention studies on kids).

Fish and depression

At least one study has shown that the more fish consumed on average per person in a country, the lower the rate of depression. Japan has very low rates of depression, for instance, when compared to countries that eat less fish like New Zealand.

Meditation and brain development

People who meditate for longer have more developed prefrontal cortices (the parts of the brain that help us concentrate). (More info)

Candy and Crime

One study carried out in the UK found that children who ate candy every day were more likely to commit crimes when they were older. (More info)

It’s another simple one, but I like it.

If you’ve got another good example, please add it to the comments. Or if you are struggling to see two explanations, don’t be afraid to ask.

Additional Activity

  • Assign one study per group of students.
  • Design an experiment that would test to see if there is a causal relationship between the two variables correlated in the study.
  • Consider the following:
    • what is the IV and DV?
    • what are the potential extraneous variables?
    • how would the IV be manipulated and the DV measured?
  • For some studies (e.g. correlating factors over time), students might have to hypothesize possible explanations for the correlation and design an experiment to test that explanation.