This week I’m looking at whether or not finding a correlation in a experiment can and does show causality ie: does finding a link/correlation between two variables prove that variable A is responsible for the change in variable B? The short answer….well no it doesn’t. There is no way of proving that some other extraneous variable in the experiment wasn’t the reason for the change. However this doesn’t mean that the two aren’t in some way linked for example it’s impossible to find a causal relationship if there wasn’t some sort of correlation between the two variables therefore correlation is essential for finding a causative relationship but it doesn’t mean that everytime there is one causation is proved. This is of course asssuming that the varibale relationship on linear. If the relationship in non linear a correlation may not be present.
In an experiment in order to find causation there needs to be high levels of control, control that is so tight that it probably would be highly difficult, if not impossible, to acheive. Think how would you be able to control the movements, life etc of participanst without breaking every ethical code in the handbook? Cause and effect means that you have a definite ‘this led to this’ relationship whereas causation is more of a ‘well they’re connected’ kind of link. This is no where near as recise and definite as what is needed for a casuative relationship to be determined. A non psychology example of when correlation doesn’t show causation is arm length. There is a high correlation between the length of people’s right arm and their left arm, the length of the persons right arm however didn’t cause the left arm to be the length it is. A psychology version of this is the example of Reiche et al’s study (2004) they looked into whetehr or not extreme psychological stress causes cancer. They found no casusative relationship between the two they did however find a strong suggestion of a correlation between extreme stress and a weakened immune system which in turn makes people more suseptible to virus associated cancers.
In conclsuion though causation is associated with correlation and is often precluded by a correlative relationship, a correlation doesn’t determine cause and effect and therefore should not be viewed as proving a cause/effect relationship.