What causes people to believe in conspiracy theories?

Right. I for one happen to believe the theory that al Qaeda conspired to execute deadly attacks on Sept. 11, 2001. That is literally a conspiracy theory. Is the process by which I came to believe that relevant to the discussion here? (If yes, I'd be happy to give more information.)

But the phrase "conspiracy theory" commonly implies (like the faked moon landing) that relatively few people believe it, generally because the evidence against the theory is fairly convincing. (Conspiracists may answer that additional evidence is not available or widely known to the public.)

See: Patternicity: Finding Meaningful Patterns in Meaningless Noise.

Interestingly two of Servant's examples aren't so much about finding an out-group to blame as deflecting blame from an in-group.

After his death, JFK became a martyr for a lot of people on the anti-war left. As such his having been assassinated by a communist sympathizer and former defector to the USSR was rather inconvenient.

In the case of 9/11 especially in a number of the countries mentioned, the need to deflect blame is even more obvious.

Spot-on with the conspiracy theorists I deal with most in real life, as parent of an autistic: anti-vaccination-ers.

Raising children does funny things to human cognition (for good evolutionary reasons). Raising a disabled child is even tougher psychologically, and finding someone to blame (in their case, amoral-profit-seeking Big Pharma and regulatory capture) provides psychological comfort.

How does this account for Moon Landing conspiracy theories?

Something more in line with your worldview is more likely. This is the point of a worldview.

Someone whose opinion you respect is more likely to be right. This is the point of respecting people's opinions.

What's the irrational decision-making you're alluding to?

Or, for example, the theory that a head of state could have illegally circumvented U.S. law by falsely claiming to be a natural-born citizen based on a fake Hawaiian birth certificate.

Haha, sorry couldn't resist. Just in case, I beg everyone to click on the links before downvoting...

It would have been good to include a few entries here along the lines of "President Nixon tried to cover up the role of his re-election campaign in the Watergate break-in".

Hmm, this leads to an idea that maybe should go over in the experiment thread- see how good the general population is in saying they believe in actual conspiracies.

This does lead to a serious issue though, how do we distinguish the actual conspiracies from the non-conspiracies? See for example Cracked's Seven Insane Conspiracies That Actually Happened.

It seems that the set of actual conspiracies is much smaller than the set of claimed conspiracies so the prior is in general low. Also, most actual conspiracies are comparatively small scale and involve short-term interests compared to the general pool of conspiracies. However, there are some conspiracy theories that fall into this pattern that are generally considered to be in the crazy category- the most obvious two would be 9/11 conspiracy theories and JFK assassination theories. Thus, without actually looking at the evidence and motivation, it may be genuinely difficult to distinguish between the real and imagined conspiracies.

While I am more interested in the latter, the former is likely the one more suited for the main goal of this "community blog".

No they aren't. When most people use the term "conspiracy theory" they generally mean larger scale, not obvious individuals, and with motivations that are more obscure. There's some level of denotation v. connotation here.

I fell into conspiratorial thinking when I was less experienced in the ways of the world. Noticing that a dark OD green helicopter with subdued markings could easily be mistaken for an unmarked black helicopter when viewed against a bright sky by an untrained observer was the start of finding my way out of that one. I remember that some things that were claimed I recognized immediately (everyone has seen black SWAT uniforms, for example) and this created a sense of credibility, while others I suspected (I was anti-internationalist back then), and I didn’t have direct knowledge of others so I didn’t try to evaluate those things but instead gave the theory a pass when it came to those. It didn’t seem like an aberration at the time, but I didn’t know about the conjunction fallacy back then. The theory certainly reinforced the beliefs I held back then, and it also gave me a feeling of superiority because I knew a secret. Yup, I was a sucker.

I've come to notice that conspiracy theories tend to be based on two or more things that are known or believed to be true, but that are not normally expected to be linked. These are then joined by a pretext for linking them in a way that would be considered outrageous to anyone that doesn’t hold the theory—some of these details are often completely inconsequential of themselves and do not necessarily add anything of substance to the theory, but adding a few high-probability elements skews the conjunction fallacy in the theory’s favor. It is worth noting that sometimes major parts of a theory are not known, but classic propaganda techniques like the “big lie” are used to cause us to evaluate their probability more highly than we should. The latter is not strictly necessary though due to the power of the conjunction fallacy. Today I take it as a red flag when I see a linkage being formed between one thing that is obvious and another that is obvious, but where the linkage is tenuous. If you have to ask “where are you going with this” the answer probably isn’t good.

This linkage is then applied to combine the theory with multiple things that are not known but are either suspected by the individual or group, or are inspired by the theory, and that can be linked by conjecture to the concept of the conspiracy. Once the basic linkage is accepted the conjunction fallacy keeps rolling and that high probability that is erroneously given to the initial theory then gets associated with all of the other craziness.

A fake conspiracy theory can demonstrate how the conjunction fallacy plays into this. "We know that we orbit the sun, and we know the sun causes skin cancer, but did you know that the earth, sun, and human race were created by ancient aliens as part of a skin cancer experiment?" Our intuition evaluates that by giving 100% to the first two things, and since we can't know the third we mentally skip it which would be like giving it 0% probability, but that's okay because 100% + 100% + 0% = 200% probability so we are believers now. Once we are believers, we give the entire idea 100% likelihood, so we know that all of the components have to be true so they all have 100% likelihood in our mind and now we know that we are alien skin cancer test subjects. But if that is true then sunscreen was probably invented by the aliens as part of their testing protocol because otherwise, why would they let us use something that would reduce our chance of getting skin cancer? So now we know that sun screen is a perverse part of the alien plot and we refuse to buy it and try to convince our friends that it is evil.

Obviously, we should instead be multiplying probabilities, where 100% 100% 0% = 0%. But that isn't the way most people tend to think. Instead most people rely on whether or not one of the foundational contexts of the theory contradicts or supports their biases, so most people who don’t follow conspiracy theories are probably not doing so because they made the correct calculation of probability but because they “know” one of these things can’t be true. For example, a geocentrist would reject the theory since they “know” that the earth doesn’t orbit the sun, while a creationist would reject it outright because they know God created the earth not aliens. However, the geocentrist might start their own branch of the theory though, like the many branches of the JFK assassination theory. For example, I suspect that one reason the Moon landing conspiracy has so few adherents is that there are so many ideological positions that it violates, even ones that tend to be mutually exclusive demographically. For example, the American right are likely to reject it because it is anti-American, while the American left are likely to reject it because it is anti-science. If everything about the moon landing were identical but the Soviets had got there first, I suspect that the American right would embrace it at rates similar to young-earth creationism.

I agree that the process is complex. I fall into conspiratorial thinking when I was less experienced in the ways of the world. Noticing that a dark OD green helicopter with subdued markings could easily be mistaken for an unmarked black helicopter when viewed against a bright sky by an untrained observer was the start of finding my way out of that one. I remember when I first encountered that set of conspiratorial beliefs that some things that were claimed I recognized immediately (everyone has seen black SWAT uniforms, for example) and this created a sense of credibility, while others I suspected (I was anti-internationalist back then), and I didn’t have direct knowledge of others so I didn’t try to evaluate those things but instead gave the theory a pass when it came to those. It didn’t seem like an aberration at the time, but I didn’t know about the conjunction fallacy back then. The theory certainly reinforced the beliefs I held back then, and it also gave me a powerful feeling of superiority because I knew a secret. Yup, I was a sucker.

I've come to notice that conspiracy theories tend to start as two or more things that are known or believed to be true, but that are not normally expected to be linked. These are then joined by a pretext for linking them in a way that would be considered outrageous to anyone that doesn’t hold the theory—some of these details are often completely inconsequential of themselves and do not necessarily add anything of substance to the theory, but adding a few high-probability elements skews the conjunction fallacy in the theory’s favor. It is worth noting that sometimes major parts of a theory are not known, but classic propaganda techniques like the “big lie” are used to cause us to evaluate their probability more highly than we should. The latter is not strictly necessary though due to the power of the conjunction fallacy. Today I take it as a red flag when I see a linkage being formed between one thing that is obvious and another that is obvious, but where the linkage is tenuous. If you have to ask “where are you going with this” the answer probably isn’t good.

This linkage is then applied to combine the theory with multiple things that are not known but are either suspected by the individual or group, or are inspired by the theory, and that can be linked by conjecture to the concept of the conspiracy. Once the basic linkage is accepted the conjunction fallacy keeps rolling and that high probability that is erroneously given to the initial theory then gets associated with all of the other craziness.

A fake conspiracy theory can demonstrate how the conjunction fallacy plays into this. "We know that we orbit the sun, and we know the sun causes skin cancer, but did you know that the earth, sun, and human race were created by ancient aliens as part of a skin cancer experiment?" Our intuition evaluates that by giving 100% to the first two things, and since we can't know the third we mentally skip it which would be like giving it 0% probability, but that's okay because 100% + 100% + 0% = 200% probability so we are believers now. Once we are believers, we give the entire idea 100% likelihood, so we know that all of the components have to be true so they all have 100% likelihood in our mind and now we know that we are alien skin cancer test subjects. But if that is true then sunscreen was probably invented by the aliens as part of their testing protocol because otherwise, why would they let us use something that would reduce our chance of getting skin cancer? So now we know that sun screen is a perverse part of the alien plot and we refuse to buy it and try to convince our friends that it is evil.

Obviously, we should instead be multiplying probabilities, where 100% 100% 0% = 0%. But that isn't the way most people tend to think. Instead most people rely on whether or not one of the foundational contexts of the theory contradicts or supports their biases, so most people who don’t follow conspiracy theories are probably not doing so because they made the correct calculation of probability but because they “know” one of these things can’t be true. For example, a geocentrist would reject the theory since they “know” that the earth doesn’t orbit the sun, while a creationist would reject it outright because they know God created the earth not aliens. However, the geocentrist might start their own branch of the theory though, like the many branches of the JFK assassination theory. For example, I suspect that one reason the Moon landing conspiracy has so few adherents is that there are so many ideological positions that it violates, even ones that tend to be mutually exclusive demographically. For example, the American right are likely to reject it because it is anti-American, while the American left are likely to reject it because it is anti-science. If everything about the moon landing were identical but the Soviets had got there first, I suspect that the American right would embrace it at rates similar to young-earth creationism.

Having the bottom line written already is not the same thing as lying. Neither is a good thing where rational dialogue is concerned, but the claim "Bush lied" has in most common moral frameworks a very different meaning than "By a host of systemic effects and severe cognitive biases, the Bush administration gave a deeply inaccurate summary of the situation." In order to be better rationalists we need to try to be aware of how frequently apparent lies are likely just severe biases.