Falsifiability and Characters In A Story

27 Jan


Another interesting study intersecting psychology with falsifiability:

You have four cards. Flip whichever cards you must to verify the rule If a card has a vowel on one side then it has an even number on the other:

E C 4 5

People do notoriously badly at this game. It’s called the “Wason selection task”. It was mentioned in the sequences a few times. But it turns out, people are much better at this version:

There are four people drinking at a bar. A police officer busts in and needs to verify the rule If a person is drinking alcohol, they must be at least 21. Which of the following must they investigate further?

Beer-drinker, Coke-drinker, 25-year-old, 16-year-old

These problems are logically identical. However, most people suggest flipping 4 while few people suggest checking what the 25 year old is drinking.

More generally, it seems that people can do very well on the Wason selection task if it’s framed in such a way that people are looking for cheaters. (Eliminating the police officer from the above story is sufficient to reduce performance.)

So it seems we have an intuitive understanding of falsifiability if we move from abstract concepts to characters in a story, actively looking for cheaters.

I’m trying to think of examples where I can use characters/cheaters to explain how falsifiability works (or otherwise called precision) other than this, but it makes me think that people would choose based on representativeness.

So instead of using marbles or dice for an example of falsifiability, I think I can use police and a lineup of usual suspects as an example.

Let’s say that someone was murdered. The police line up the usual suspects of mob hitmen. In this case, we have four suspects.

Nate has a tendency to keep it simple. He always uses a .9mm gun to shoot victims. Jerry likes to either strangle or poison his victims, preferring to keep things from getting messy. Bob is known to use any means he can to kill his victims: guns, knives, poisoning, arson, strangling, bombs, throwing people out of airplanes, etc.Dan either strangles or shoots victims and doesn’t bother with any other methods.

The person murdered was found strangled. So, based on this information, and keeping things simple for this thought experiment, which person likely did it? We can rule out Nate since he never strangles victims. Bob, Dan, and Jerry all use strangling, but since Bob is all over the place with his method of taking out people he is the least likely to have strangled someone in this case. Dan and Jerry are equally as likely to have been the one to do it.

Obviously, you would have to also take into account prior probabilities, like how often each person actually kills someone for the mob if this were a real situation. But with all else equal, Nate is the least likely to have done this hit, followed by Bob, and then Dan and Jerry tie for most likely.

Of course, this remains to be seen whether people actually do better at eliminating Nate, placing Bob in second to last, and focusing on Dan and Jerry. I’ll have to ask some friends or something. But one point that I think might hinder it is representativeness; they might see Bob’s penchant for variety in his choice of murder and implicitly use that large number as a substitute for prior probability. In other words, they might see the method of murder and substitute it with the number of murders. In that view, Nate has only killed one person, Dan and Jerry have killed two, and Bob has killed a multitude… even though the number of people each person has murdered is never given in this thought experiment.

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Posted by on January 27, 2014 in Bayes, cognitive science, rationality


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