That caught your attention, didn’t it?
And on the face of it, it’s true and backed up by facts and statistics:
- About 150,000 people died worldwide yesterday.
- Of these, none had read my blog yesterday.
- The few people who did read my blog yesterday are still alive today.
Conclusion: Reading my blog keeps you alive.
Or does it? You immediately sense that a few things are fishy here, even if you believe that I know each one of my readers personally and know that they are alive: Of the people who died yesterday, many had no access to the internet. If they also live in countries with higher mortality rates, their chance of death is of course higher than those of the bulk of my readers who are in the USA and Europe (see the flag counter on the right hand side). This increased mortality risk might have less to do with lack of a WLAN, but with lack of food or the danger of diseases or with a war. On the other hand, of the people who read my blog, some might be couch potatoes who never venture outside. They don’t have the risk of car accidents, of being shot or struck by lightning. But again, the reason for their longevity is not reading my blog, the reason is staying inside.
You see that just because two events (reading my blog and staying alive) happen at the same time or to the same people, there is not necessarily a causal connection, as long as there are other possible more causal connections (like the country where you live or the dangers that you are exposed to, in this example).
Correlation is not causation!
In fact, correlation does not even imply causation.
With a silly example like the one I have chosen, this is obviously clear. But keep this sentence in mind when you read or hear about the latest “new study” that tries to show a link between something and cancer or something and crime or something and divorce. This is especially true for the social sciences because human interactions are so complex that they will rarely be open to monocausal explanations.
A few more examples that we come across regularly:
- If a study suggests that married people are happier, this is presented as proof that marriage is a way to happiness. However, it could simply mean that happy people find partners more easily than grumpy ones and therefore get married more often.
- Children who watch TV or play computers too much, have psychological problems. Parents use this as an argument to cut down on your computer use. In fact, it might be interpreted the other way round: Children who already have psychological problems, don’t want to interact with other children and thus prefer to sit in front of a screen.
- Babies who have been breast-fed will have a higher IQ. Proponents of breast-feeding will cite this again and again and probably even petition for tax relief for breast-feeders. However, if we look at the group of breast-feeding mothers, these might be the mothers who generally take more time for their babies, have a closer emotional bond, will be more supportive and will also read books to the child. All of which might have a greater impact on the IQ than where the milk comes from.
To be clear: What these studies pretend to show, could be true. But it could also be false. Even the opposite could be true. – Without the context of many other studies, they just don’t tell us anything of value.
More critical thinking, please!