Thinking Clearly #2: Conjunction Fallacy

I bought a book.”The Art of Thinking Clearly”, by Rolf Dobelli. It’s a good book. It’s filled with 99 chapters, each describing a certain psychological phenomenon that negatively affects us all. I will be randomly picking a chapter, explain how it works, and use an example from my own experience in every blog. Have you got a good example? Leave a comment!

Chapter 41: Conjunction Fallacy
We have an innate attraction to ‘harmonious’ or ‘plausible’ stories. The more convincingly, impressively or vividly something is portrayed, the greater the risk of false reasoning. What is more likely? A) ‘Seattle airport is closed. Flights are cancelled’. B) ‘Seattle airport is closed due to bad weather. Flights are cancelled’.  Most people will opt for B. Unfortunately, it is the wrong answer.” (p.127-128)

Why is it the wrong answer? Because option A is much more likely to happen. The Airport could be closed due to a multitude of option, including bad weather. However, option B excludes all of these options, instead going for a single option. This option might be more plausible than, lets say, a terrorist strike or an incidental fire, but the in option A, all of these options are combined into one outcome, making it statistically more plausible.

Consider this one: A) will only be succesful if I write consistently, or B) will only be succesful if I write consistently about videogames. I write about a plethora of topics, ranging from politics to videogames. Option A doesn’t state I have to write about one subject, and it doesn’t say which subject that should be. I could write about the many subjects I do now, or choose any of the subjects and devote myself to that one. Writing consistently about politics could be just as effective as writing only about videogames, therefore, option A would be more likely to happen.

It also happens the other way around: sometimes you automatically fill in the blanks. Have you ever read a news article about a street robbery and thought the perpetrator would probably be of a foreign descent? This might be a little racist, but I have. The fact is, a ‘foreigner’ is relatively more likely to rob someone, however, there’s maybe 2 million coloured people in the Netherlands, while there are 15 million natives. Again, statistically, the ‘white man’ would (in the end) be more likely to commit a crime, even if 50% coloured people would commit crimes and just 10% of the natives would.

Thinking this way creates a lot of animosity and distrust between different groups of society. It is not easy to get rid of this way of thinking. However, sometimes you just have to stop and think: is this a conjunction fallacy?

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