Twin study suggests rationality and intelligence share the same genetic roots - the study suggests that being irrational, or making illogical choices, might simply be another way of measuring lower intelligence.

[u/mvea]

https://www.psypost.org/twin-study-suggests-rationality-and-intelligence-share-the-same-genetic-roots/

[u/Capybara-at-Large]

I already know this hypothesis has severe limitations of application because of the amount of highly intelligent people who also have a severe mental illness.

Surely individuals like John Nash and Isaac Newton—who historically made highly irrational choices due to a mental illness that causes delusions and severe lapses in logical reasoning—cannot also be considered low IQ.

There are countless people with schizophrenia, bipolar, and depression who make irrational choices on account of their illness yet are often key contributors to advances in science and culture.

I also believe rationality only highly correlates with intelligence for this reason.

There are too many instances where someone’s ability to be rational is completely gone while their IQ remains intact.

[u/isaac_the_robot → u/Capybara-at-Large]

Are they making irrational decisions, or could they be making rational decisions based on incorrect starting information? A person who is experiencing paranoid delusions could potentially still make rational decisions to protect themself from a threat that doesn't actually exist.

[u/caffa4 → u/isaac_the_robot]

I’m not gonna claim to be highly intelligent/have a genius IQ, but I’d say my intelligence is one of my strengths. I also have bipolar disorder and have acted quite irrationally. Even based on delusions I experienced. And I think the element of impulsivity leads to irrational actions as well, not just delusions.

I spent thousands of dollars I didn’t have. I knew I didn’t have it and I had no way to pay it, I just did not care. I overdosed on dozens of pills when I had delusions of grandeur and believed I couldn’t die—say I was acting on my delusions, does that make it rational to do something that surely isn’t healthy either way? I booked a flight to NYC for less than 12 hrs later, less than a week after having ankle surgery. The trip alone could simply just be impulsive, but doing that right after surgery kind of pushes it into irrational territory. I showed up absolutely drunk to a bunch of exams my senior year of college, no delusions involved, but simply not rational. Honestly I could keep going on but I’m sure you get the point.

A rational person considers consequences. When I’m in an episode, it’s like that part of my brain is just gone.

[u/SimoneNonvelodico → u/caffa4]

Saying two things correlate though doesn't mean they are 1:1 present together. Being a man correlates with greater upper body strength, but if I played arm wrestling with the women's weight lifting champion I'd get destroyed.

As I said, I think the main reason for this correlation is actually quite simple: being intelligent is a requirement to even know what the rational decisions are. It's not enough to ensure that you make them, but it's the bare minimum necessary. If you're too dumb to realize the consequences of your actions, you couldn't be rational even if you tried.

[u/caffa4 → u/SimoneNonvelodico]

That makes sense! I was just providing additional context in how people with mental illness still might not act rationally and that there’s more to it than a rational/irrational response to delusions.

[u/alsuhr → u/isaac_the_robot]

I agree. It's worth rethinking whether rationality is something we can have some "amount" of. As observers we are just as responsible for understanding under what conditions someone might behave as they do, as they are responsible for violating our expectations of "rationality". A piece I really liked that discusses this is "Is human cognition adaptive?" (Anderson 1991, BBS)

[u/Frosti11icus → u/alsuhr]

Most decisions are rational from the perspective of the person making them. Calling a decision irrational is more of a privilege of an outside observer. There’s too many variables involved for outsiders to make that call. Making correct Vulcan like decisions requires that your story be written in such a way that you can make correct Vulcan like decisions, but most people don’t get that life.

[u/redsalmon67 → u/isaac_the_robot]

As someone who suffers from bipolar disorder and had a pretty serious bout of psychosis only a few years ago I feel like this touches on what of feels like from the perspective of a lot of mentally ill people. To the outside world the things we’re doing seem irrational and random but from the perspective of someone who for example, thinks people can read their thoughts, becoming agoraphobic makes perfect sense.

[u/Anna-Politkovskaya → u/isaac_the_robot]

I have an ADHD diagnosis: my thinking is rational but I don't make rational decisions based on the correct information I have.

I stress about not finishing my thesis and missing deadlines. I could solve these issues by working on my thesis and checking the deadlines, but I postpone things till the last moment, which stresses me more.

From a neurotypical outsiders perspective, I may seem dumb. I know the solutions to my problems, yet due to a neurological condition, I make irrational choises. 

[u/LuckyFogic → u/isaac_the_robot]

I'd like to think I'm slightly above average when it comes to intelligence, at least when I was more academically involved. When psychosis kicks in, self awareness becomes an enemy. I know I'm acting irrationally, I readily admit my symptoms match the majority of diagnostic criteria. My upbringing, socioeconomic status, family relations, all of it tracks. I understand it conceptually, but "snapping out of it" means ignoring everything my body is telling me. I know my life is not at immediate risk, that I'm seeing patterns in the static, but I'm left either trusting my senses or thoughts. Either way I'm wrong, I just can't figure out which to trust more.

When you're hyper aware and introspective it's easy to find evidence to support any internal claim.

[u/Agreeable_Cheek_7161 → u/Capybara-at-Large]

There are too many instances where someone’s ability to be rational is completely gone while their IQ remains intact.

I do think it's important to point out that they're talking about general intelligence measured in various ways, and NOT just IQ

[u/ZenPyx → u/Agreeable_Cheek_7161]

"Cognitive ability was measured using a combination of tests that assessed vocabulary, numerical reasoning, and the ability to identify patterns in sequences of letters and numbers. These types of tests are commonly used to gauge different aspects of intelligence." -I mean this literally describes an IQ test

Edit - the paper literally lists the test as an IQ test. In fact, the author of the paper says the term "IQ test" 4 times in the article posted on this sub

[u/Agreeable_Cheek_7161 → u/ZenPyx]

While true, it is important to point out they explicitly aren't measuring IQ here

[u/ZenPyx → u/Agreeable_Cheek_7161]

Right, but they are just measuring all of the factors that also go into IQ test measurement? It's the same thing, they aren't measuring anything which isn't assessed by the IQ test, which is rightly not considered to be a great metric for these things

[u/Agreeable_Cheek_7161 → u/ZenPyx]

Sure, but there's very clearly a reason they aren't just using an IQ test but instead using a combination of tests to measure roughly the same thing. In theory, yeah, they measure similar things, but the method used to test it is decidedly different, even if similar in nature

[u/ZenPyx → u/Agreeable_Cheek_7161]

It's literally the same thing though... they are using the exact same testing metrics. The fact that they are so intentionally vague about what they are testing for exactly, and that they haven't mentioned what testing protocols they actually used, would lead me to believe they actually administered IQ tests, but regardless, they are conflating intelligence, which is unmeasurable, with performance on a narrow range of tests.

[u/EveningAnt3949 → u/ZenPyx]

This is not a comment on the research, but a comment on IQ tests: they tend to be bad at measuring intelligence.

And of course historically, many of the people who used IQ tests to classify children acknowledged this.

[u/ZenPyx → u/EveningAnt3949]

The research actually uses an IQ test - in fact, the author of the research talks a lot about IQ tests in the interview he has in this article. So it is a comment on the research.

[u/EveningAnt3949 → u/ZenPyx]

Please read my comment again, and this time try to use reading comprehension. Or simple logic.

Don't be that guy arguing about intelligence with showing a lack of intelligence.

[u/anima173 → u/Capybara-at-Large]

Exactly. And there are many historical examples of people intelligent people doing irrational things. Correlation doesn’t equal causation. This study is based on a logical fallacy ironically enough. It also completely negates types of intelligence that aren’t based on logic, like emotional intelligence or creative intelligence.

[u/plopliplopipol → u/anima173]

if the title is true they suggest an external common factor and not a causation.

[u/0akleaves → u/Capybara-at-Large]

I mostly agree but an important note is to be careful using depression as an example of mental illness that makes people act irrationally. Problem is that there is a pretty decent body of evidence showing that depression is linked to an abnormally clear and accurate understanding of events and statistics along abnormally LOW levels of self delusion or “wishful thinking”. In other words the “irrationality” all too often associated with depression could very well be argued to be a refusal to entertain a lot of the common societal delusions/irrational beliefs like “it will all work out for the best” etc.

[u/MikeSifoda → u/Capybara-at-Large]

Intelligence has many dimensions, being outstanding in just one of them doesn't make you all that smart and you won't be functional, you will need plenty of support. Newton didn't really have to fend for himself, did he? He was a rich englishman who didn't need to be functional to live.

[u/Mylaur → u/Capybara-at-Large]

If they're making irrational decisions due to a mental illness, isn't it because of that mental illness...? Thus the positive correlation between intelligence and rationality doesn't sound valid in that case.