Fallacy: Misleading Vividness
Description of Misleading Vividness
Misleading Vividness is a fallacy in which a very small number of particularly dramatic events are taken to outweigh a significant amount of statistical evidence. This sort of "reasoning" has the following form:
- Therefore events of type X are likely to occur.
Dramatic or vivid event X occurs (and is not in accord with the majority of the statistical evidence) .
This sort of "reasoning" is fallacious because the mere fact that an event is particularly vivid or dramatic does not make the event more likely to occur, especially in the face of significant statistical evidence.
People often accept this sort of "reasoning" because particularly vivid or dramatic cases tend to make a very strong impression on the human mind. For example, if a person survives a particularly awful plane crash, he might be inclined to believe that air travel is more dangerous than other forms of travel. After all, explosions and people dying around him will have a more significant impact on his mind than will the rather dull statistics that a person is more likely to be struck by lightning than killed in a plane crash.
It should be kept in mind that taking into account the possibility of something dramatic or vivid occuring is not always fallacious. For example, a person might decide to never go sky diving because the effects of an accident can be very, very dramatic. If he knows that, statistically, the chances of the accident are happening are very low but he considers even a small risk to be unnaceptable, then he would not be making an error in reasoning.
Examples of Misleading Vividness
Jane: "I've been thinking about getting a computer. I'm really tired of having to wait in the library to write my papers."
Bill: "What sort of computer do you want to get?"
Jane: "Well, it has to be easy to use, have a low price and have decent processing power. I've been thinking about getting a Kiwi Fruit 2200. I read in that consumer magazine that they have been found to be very reliable in six independent industry studies."
Bill: "I wouldn't get the Kiwi Fruit. A friend of mine bought one a month ago to finish his master's thesis. He was halfway through it when smoke started pouring out of the CPU. He didn't get his thesis done on time and he lost his financial aid. Now he's working over at the Gut Boy Burger Warehouse."
Jane: "I guess I won't go with the Kiwi!"Joe and Drew are talking about flying.
Joe: "When I was flying back to school, the pilot came on the intercom and told us that the plane was having engine trouble. I looked out the window and I saw smoke billowing out of the engine nearest me. We had to make an emergency landing and there were fire trucks everywhere. I had to spend the next six hours sitting in the airport waiting for a flight. I was lucky I didn't die! I'm never flying again."
Drew: "So how are you going to get home over Christmas break?"
Joe: "I'm going to drive. That will be a lot safer than flying."
Drew: "I don't think so. You are much more likely to get injured or killed driving than flying."
Joe: "I don't buy that! You should have seen the smoke pouring out of that engine! I'm never getting on one of those death traps again!"- Jane and Sarah are talking about running in a nearby park.
Jane: "Did you hear about that woman who was attacked in Tuttle Park?"
Sarah: "Yes. It was terrible."
Jane: "Don't you run there everyday?"
Sarah: "Yes."
Jane: "How can you do that? I'd never be able to run there!"
Sarah: "Well, as callous as this might sound, that attack was out of the ordinary. I've been running there for three years and this has been the only attack. Sure, I worry about being attacked, but I'm not going give up my running just because there is some slight chance I'll be attacked."
Jane: "That is stupid! I'd stay away from that park if I was you! That woman was really beat up badly so you know it is going to happen again. If you don't stay out of that park, it will probably happen to you!"
Bill and Jane are talking about buying a computer.
LET'S GET A STATISTIC ON THIS: JUXTIPOSED, THE AIRPLANE DEATH THING. TO mEN OR WOMEN STANING ON A GOLF COURCE WITH A NINE IRON RAISED TO THE HEVENS, DURING A LIGHTINING STORM! WHAT NOW IS MORE DEADLY FLIGHT OR PLAYING GOLF?
Fallacy: Post Hoc
Also Known as: Post Hoc Ergo Propter Hoc, False Cause, Questionable Cause, Confusing Coincidental Relationships With Causes
Description of Post Hoc
A Post Hoc is a fallacy with the following form:
- A occurs before B.
- Therefore A is the cause of B.
The Post Hoc fallacy derives its name from the Latin phrase "Post hoc, ergo propter hoc." This has been traditionally interpreted as "After this, therefore because of this." This fallacy is committed when it is concluded that one event causes another simply because the proposed cause occurred before the proposed effect. More formally, the fallacy involves concluding that A causes or caused B because A occurs before B and there is not sufficient evidence to actually warrant such a claim.
It is evident in many cases that the mere fact that A occurs before B in no way indicates a causal relationship. For example, suppose Jill, who is in London, sneezed at the exact same time an earthquake started in California. It would clearly be irrational to arrest Jill for starting a natural disaster, since there is no reason to suspect any causal connection between the two events. While such cases are quite obvious, the Post Hoc fallacy is fairly common because there are cases in which there might be some connection between the events. For example, a person who has her computer crash after she installs a new piece of software would probably suspect that the software was to blame. If she simply concluded that the software caused the crash because it was installed before the crash she would be committing the Post Hoc fallacy. In such cases the fallacy would be committed because the evidence provided fails to justify acceptance of the causal claim. It is even theoretically possible for the fallacy to be committed when A really does cause B, provided that the "evidence" given consists only of the claim that A occured before B. The key to the Post Hoc fallacy is not that there is no causal connection between A and B. It is that adequate evidence has not been provided for a claim that A causes B. Thus, Post Hoc resembles a Hasty Generalization in that it involves making a leap to an unwarranted conclusion. In the case of the Post Hoc fallacy, that leap is to a causal claim instead of a general proposition.
Not surprisingly, many superstitions are probably based on Post Hoc reasoning. For example, suppose a person buys a good luck charm, does well on his exam, and then concludes that the good luck charm caused him to do well. This person would have fallen victim to the Post Hoc fallacy. This is not to say that all "superstitions" have no basis at all. For example, some "folk cures" have actually been found to work.
Post Hoc fallacies are typically committed because people are simply not careful enough when they reason. Leaping to a causal conclusion is always easier and faster than actually investigating the phenomenon. However, such leaps tend to land far from the truth of the matter. Because Post Hoc fallacies are committed by drawing an unjustified causal conclusion, the key to avoiding them is careful investigation. While it is true that causes precede effects (outside of Star Trek, anyways), it is not true that precedence makes something a cause of something else. Because of this, a causal investigation should begin with finding what occurs before the effect in question, but it should not end there.
Examples of Post Hoc
- I had been doing pretty poorly this season. Then my girlfriend gave me this neon laces for my spikes and I won my next three races. Those laces must be good luck...if I keep on wearing them I can't help but win!
- Bill purchases a new PowerMac and it works fine for months. He then buys and installs a new piece of software. The next time he starts up his Mac, it freezes. Bill concludes that the software must be the cause of the freeze.
- Joan is scratched by a cat while visiting her friend. Two days later she comes down with a fever. Joan concludes that the cat's scratch must be the cause of her illness.
- The Republicans pass a new tax reform law that benefits wealthly Americans. Shortly thereafter the economy takes a nose dive. The Democrats claim that the the tax reform caused the economic woes and they push to get rid of it.
- The picture on Jim's old TV set goes out of focus. Jim goes over and strikes the TV soundly on the side and the picture goes back into focus. Jim tells his friend that hitting the TV fixed it.
- Jane gets a rather large wart on her finger. Based on a story her father told her, she cuts a potato in half, rubs it on the wart and then buries it under the light of a full moon. Over the next month her wart shrinks and eventually vanishes. Jane writes her father to tell him how right he was about the cure.