psychology

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PSY1010_W1_Interpreting_Correlations.html.zip

PSY1010_W1_Interpreting_Correlations.html

The tendency to interpret correlations in terms of cause and effect is a common error.

We have a tendency to look for explanations for the things that we see in our environment. This tendency leads to the formation of illusory correlations in our own minds. This means that when two things are related to each other because of a third factor that causes both, we tend to see a causal relationship between the first two. This is especially true when we aren't really aware of the existence of the third variable.

A classic example of an illusory correlation that many people have is when a couple adopts a baby, it increases the likelihood that they will have their own biological baby. Almost everyone knows a couple to whom this has happened. We conclude that adopting can improve fertility. One explanation is that the newly-adopted baby reduces the couple's stress so much that they are able to conceive - apparently given by someone who's never had a new baby! Most couples' stress levels go up, not down following the birth of their first child.

The point is that our tendency to focus on cases that support our conclusion (couples who had a biological child after adopting), and to ignore cases that refute our conclusion (couples who adopt and never have biological kids; people who have biological kids and never adopt; couples who never have biological kids and never adopt), leads us to see causal links that don't really exist.

How could a study be conducted to draw a cause and effect conclusion? The only way to draw a cause and effect conclusion is to do a controlled experiment. When all variables are controlled, and one variable that affects the subject is manipulated, and there is a difference in the outcomes, then we can conclude that manipulations caused the differences. We must have control to be able to claim that one variable caused another.

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