What is the name of this fallacy?

I think it is neither Neglect of probability nor Hindsight Bias (the wiki page of which I was reading having followed Sr Siete’s link).

The former is about a tendency to disregard probabilities when making decisions. The latter about a tendency to overestimate probabilities of outcomes after
they are known (admittedly “my” case could be construed as a very extreme case of hindsight bias, but I think that would be cramming too much meaning into one term).

I’m not saying wikipedia is the font of all knowledge but their Logical Fallacies page distinguishes between two types of fallacy : Formal Fallacies (which Chessic Scene and others have taken to be the definition of “fallacy”) and Informal Fallacies (ad hominem, ad populum, Historian’s Fallacy amongst them).

I don’t think it is too much to call this case a logical fallacy, it is after all based on the fallacious “logic” that the outcome determines what a prior decision should have been. “It came up 6 therefore you should have chosen 6”.

Still, Fallacy, Informal Fallacy or simple Error, this thing deserves a name, and so far “Historian’s Fallacy” seems to fit closest.

The fact that the historian’s fallacy is an informal fallacy has nothing to do with the issue. Informal fallacies are perfectly real and recognized fallacies. Indeed, most fallacies are informal, and, probably, most fallacious reasoning is due to informal fallacies. All the word “informal” means, in this context, is that the fallacy is not one that arises from some error in the logical form of the argument, but rather from some error about the content or meaning of the terms involved.

The reason that no fallacy can be pinpointed in the scenario presented in you OP is that there is no argument presented that might be fallacious. There may be one in the speaker’s head, but we don’t know what it is, so we cannot pinpoint which, if any, fallacy or fallacies it commits.

Furthermore, if we interpret the speaker’s statement to mean “You would have done better if you had chosen six,” which seems to me to be the most natural interpretation, it is in no way false, and so there is no reason to think it might be the result of fallacious reasoning. If we interpret it to mean something like “you are a fool because you didn’t choose six,” then it is indeed false, and it might be the conclusion of some sort of fallacious reasoning inside the speakers head. But we can only speculate about that.

If, as you do in the rest of your post, you change your example after the fact to make your original erroneous use of “fallacy” look appropriate, it is you who are arguing fallaciously.

Don’t try this in a logic class. You will lose points.

Incidentally, this

is undoubtedly fallacious, because it derives an “ought” (“should” amounts to “ought to”) from “is”, from statements of observable fact. To be made valid it requires a further premise about desired outcomes. If the premise “You wanted your chosen number to match the actual result of the roll of the die,” is added then the argument (with a few more steps) becomes valid, and the conclusion is true. I can only speculate that you think it is not true, and that therefore any argument leading to it might be fallacious, because you are adding a suppressed rider to the conclusion: something along the lines of “and you were thus a fool not to have chosen six”.

Actually, now that I think about it, although I believe that the OP was trying to come up with an example of the “Historian’s fallacy,” but what he (or she, I don’t know) came closer to was “overly-broad generalization.”

This is the one that goes

  1. I see a cat
  2. the cat is white
    therefore, all cats are white.

It’s not immediately obvious, but what is happening in the mind of the person who criticizes the chooser for not picking six, is something like this:

  1. you want to predict the roll of a die
  2. you roll it once and it comes up six
    therefore, it is most likely to come up a six, and that’s what you should predict.

That actually might be true if it isn’t a fair die (ie, it’s weighted to come up six more often), but one roll cannot determine that, just like one cat cannot determine the color of all cats.

Like I said, I don’t think this was the OP’s intention-- the OP wanted an example of the Historian’s fallacy, and just erred in generating a good example. But I think that’s the source of the disagreement.

A better example of the situation the OP was trying to come up with, I think, would be something like this: you can bet one 1-5, or six. You took stats in college (but not, apparently, psychology), so you bet on 1-5. After losing five times in a row, you begin to suspect that the die is not fair; had you known that from the beginning, you would have bet on six every time.

Your strategy failed, therefore it was a bad strategy.” is a logical fallacy. Also very similar are “My strategy succeeded, therefore I had a good strategy.” and “Based on a tiny number of observations, I will draw conclusions about whether one strategy is better than another.” The last one seems to be a variation of the Hasty Generalization Fallacy.

  1. I see a test of your strategy.
  2. Your strategy failed the test.
    therefore, your strategy always fails
    (hence, you chose a bad strategy)

I’m gonna say this is halfway between the Historian’s Fallacy and the Hasty Generalization Fallacy.

This is very close to the Historian’s Fallacy and Hindsight Bias, but it’s actually called the Outcome Bias: judging the quality of a decision by its outcome, rather than on the information available at the time the decision was made.

The Historian’s Fallacy involves judging based on information *other than the outcome *that was not available to the decision-maker (I recently bought a car just days before the manufacturer recalled it for a potentially deadly defect. Had I known that they were planning the recall, I wouldn’t have bought it, but that wasn’t a bad decision, because I didn’t know about the upcoming recall at the time.)

Hindsight Bias involves modifying your interpretation, after the outcome is known, of the facts that were available at the time the decision was made by giving more weight to those that indicate the outcome you now know about. Knowing the outcome makes it easier to connect the dots that point to that outcome and claim that you “should have known” it would happen. (In reading a mystery novel, once you know the ending, it’s suddenly easy to toss aside all of the red herrings and focus in on the real clues that you hadn’t even noticed before.)

You can look at the argument several ways, depending on what you believe the person is actually saying. If you assert that he is saying “at the time of the decision picking 6 over any other number would have been a better choice,” this is obviously a fallacy, as the gambler didn’t know it would turn up 6. This would I honk qualify as the historians fallacy.

However if you interpret the argument to mean “if you had picked a 6 instead of x, you would be better off now,” it is different. This argument would be a hypothesis contrary to fact, as picking a 6 could have altered the extremely sensitive initial conditions involved in a dice roll and altered the result.

What I suspect the argument is intended to mean is “if you had picked 6 instead of x, and all initial conditions affecting the dice roll remained the same, you would be better off.” Whether this is logically sound depends on whether you believe choosing a number will always have an effect on the initial conditions. In my opinion the conditions are sensitive enough, that for most situations choosing may have an effect, therefore without more information (which may be impractical to obtain) we cannot say that picking 6 over x would have benefited you more. (I’m assuming this would be incompatible premises, not sure if there’s a particular name for that)

If we alter the experiment slightly, such that the dice is rolled, and the result concealed before the betting takes place, then the argument has merit. If the betting takes place after the roll then the betting itself cannot affect the outcome, and it would be reasonable to use the argument.

I personally don’t see it as a fallacy myself, just a banal and obvious statement of fact. It’s true. Given the result, you should have chosen a six. Obviously, you picked the correct course of action given the information known at the time. I don’t read “you should have chosen six” as a logical argument at all. It’s not. It’s just rubbing the loss in your face.

There’s another possibility we haven’t considered yet. One way to look at gambling is this: When you win, it’s because Fate smiled upon you; when you lose it’s because the Gods felt you hadn’t earned their favor. Using this concept, there is no such thing as the optimal strategy in deciding how to bet. There is only attempting to divine the whims of supernatural being which control the universe. When you bet 1-5 and lose, it’s not because you’re bad at math, it’s because you’re bad at theology.

I personally think this line of reasoning is total horse hockey, but we can’t deny that there are some people who view the universe this way. I’ve seen it argued that this is why mainstream religions hate gambling so much. It’s because they don’t like the competition.

Nice post. Wiki has an article on outcome bias:

Methinks Outcome Bias deserves to become a meme.

Luckily I’m not in a logic class.

I’m going to let drop the accusation that I am trying to worm, I clarified what I understood the situation to be.

You’re kidding right? You mean that it’s NOT obviously implied that one wishes to match the eventual outcome with one’s choice?

That certainly looks like the thing, so thanks.

A number of posts have been made here that I hadn’t seen until now (though I was sure that I had been monitoring the thread), so thanks everyone for your input.

I think there are more comments I’d like to respond to, and maybe some further questions, but it is stupid late and I’m not at my posting best.

Stupid message board just ate my post because my “token had expired”. WTF?

njtt, I am quite bothered by your accusation that “I changed my example after the fact”, not because some person on the internet thinks I did it for nefarious reasons, but because it shows that I don’t see the world as others do.

I cannot help but read into the OP’s “Should have chosen 6” an implicit construction “It came up 6 therefore you should have chosen 6”.

And, as you point out, there are other underlying assumptions that I made too, namely:

You prefer to win rather than not
The rules state that in order to win you want your choice to match the outcome
The outcome was 6
You should have chosen 6

(I’m sure there are further assumptions, for instance: the assumption that the remark, “Should have chosen 6” is addressed to me. It might be a fun game (but perhaps not) to find even more. Okay, a last example: the assumption that “Should have chosen 6” is English and not Martian for “Hard luck, you really did make the right choice”.)

But YES, that’s really what I would take to mean “Should have chosen 6” in real life.

Jeesh! You assume a lot TGU! I assume I hear you say.

I don’t think so. I don’t see any other possible meaning to “Should have chosen 6”. If it’s meant to be something purely informational; “had you chosen 6 you would have won” then:

a) no new information is conveyed being a (re)statement of the trivial consequence of the given rules

b) it is wrong (see my post #16)

So what am I missing? If my assumptions are too much, what else could the statement “Should have chosen 6” be taken to mean? And how could one reasonably respond?