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Tuesday, May 05, 2009

Yet another common cognitive error

Part 3 - Post hoc ergo propter hoc
Or in plain English After therefore because of

This is the third and probably the most common, hardest to combat fallacy we can make. It comes from not properly understanding cause-effect relationships so that it could look like event A was the cause of C, while in reality B was the cause.


Quacks in particular like this fallacy very much. It is the root of most folk wisdom, miracle cures, and superstition. If you have a headache and take a pill then your headache disappears then it would be logical to think that the pill did cause the headaches disappearance. However if you instead of taking the pill spun around four times, did some arcane incantations and sacrificed a goat, and then your headache disappeared, it too would be easy to think that it was the cause.

As one example of how easy it is for us to fall into this trap, let me use an example from one of my homeboy psychologists, B.F. Skinner.

Skinner put a pigeon in a box along with a machine that dispensed food at random intervals. The pigeons learned to associate whatever behaviour they had just been doing as food arrived, with food. Thus they would try to do the same thing again thinking it led to receiving food. For example if a pigeon had just been looking over its shoulder when food arrived, it would keep looking over its shoulder in an attempt to receive food.
Sounds simple enough, this is a pigeon after all, they have a brain the size of a fingernail so...

Well, not as much. The experiment has been replicated on humans time after time, and works like a charm. You can place a human in such a box with a score display, and tell him that his score will be based on his actions and it's up to him to figure out the scoring formula. Even if score here too is given out randomly, a person will keep trying the same actions that he did just before receiving points, much rather thinking that he did the process wrong instead that the whole process was faulty.

The world is a complicated place with hundreds of factors at any time affecting what is happening. Determining the exact cause and effect of many scenarios is downright impossible. Sure, you can think that pressing the brakes of your car slows it down, and that is a fair assumption. However, when you start thinking that saying 'Baby needs a new pair of shoes' and kissing the dice before rolling them will lead to a good roll, then that's less probable. Do it once and it gets stuck in your head as a possible cause and you keep doing it.

We all have our rituals, lucky charms and quirks that we do. There isn't much of a miracle cure to make yourself immune to this thought. No matter how skeptical you can be, you may always have the thought "but what if it was kissing the dice that helped them come up twelve". We live in a deterministic universe, but our senses and understanding are not sufficient to parse and understand all the cause-effect relationships when they are not immediately obvious. We mentally eliminate things that are not obviously the cause. We also have troubles seeing multiple causes for a single effect, or multiple effects coming from a single cause.

And this is a pitfall that we will fall into time and time again. We need our reasons. If something happens we as humans have to go and search for the reason for it. If we can't immediately and obviously find it, we can and will draw a mistaken conclusion from it and end up with the wrong cause-effect relationship in our head. And then we try to replicate it later.

1 comment:

  1. "We live in a deterministic universe" really ? ever heard of chaos ?

    ReplyDelete