Believing in religion shows a fundamental lack of critical thinking ability, so on that note yes religious people are less intelligent. I do think gullibility is a component of overall intelligence.

Correlation != causation

I think it promotes allegiance to hierarchy.

And excuses away bad people from being held accountable. "My god will punish them so no point in doing anything" or "they will be punished in the next life".

Many religions promote wealth inequality. Either by saying poor people deserve to be poor from their past life behaviors. Or because it's part of god's plan for them to struggle to be taught a lesson. Or personal punishment for not following the religious doctrine.

Those mindsets can bleed into just about any aspect of life and certainly reduce people's likelihood of questioning things or critiquing things.

I also think people like easy simple answers. And they are happy to believe a being created humans. Than be willing to understand biology and evolution which is much more complicated than a religious answer.

In that way it also reduces seeking and learning knowledge.

Infact it actively discourages it as these things contradict their religion so people avoid it.

Agreeing to reject reality has all kinds of unpleasant side effects

It certainly harms the Critical Thinking capability.

I mean, religion generally encourages a lack of skeptical thinking, logic, reasoning and curiosity. All of these are skills generally associated with intelligence.

I'm not going to watch the video, simply due to the clickbait-y screencap but I was raised in a southern baptist household and from the time I could sit still in a pew, I can remember being taught two things. First, you have to believe in the existence of god in spite of the fact that nothing will happen in your life to prove his existence. Secondly, if you ever began to doubt the existence, you would were courting an eternity in the Weber grill-style hell for all eternity.

Of course conditioning people from birth not to think about things but just believe what you're told is going to result in people that are poor critical thinkers. This seems like a Captain Obvious-level revelation.

I propose that it's the opposite.

I don't think you can make a smart person turn off their brain. I don't think religion will stop them from asking questions they don't have answers to.

I think the smart ones figure out what's going on, and GTFO as soon as they can. The ones who stick around never had a chance to begin with.

The question remains unanswered by the video

I haven't seen the video and probably won't. With that said…

Define intelligence first. Is it having knowledge on many topics? Is it problem solving? is it a mensa result? By moving the goal post you can prove whatever.

I am not from the states so my cultural context might make me think differently in this aspect. I have met many religious people over my life. And as a convinced atheist I have also had many friendly discussions on the topic with them. Some of those people were what I'd consider really intelligent. Religion has as much to do with your cultural context as it does with intelligence and some people continue believing in their religion without really thinking too much of it, not for lack of intelligence, but out of habit.

What I want to say with all of this is that, as with many of these studies, it doesn't really mean much more than at best some probability correlation. Which at a personal level won't mean anything. You might be an atheist and not be… very bright. Or be very intelligent and still religious. Just like I have met people with scientific background and high level studies belive in homeopathy.

Do not make the mistake of thinking an atheist is automatically smarter than a religious person. It is not that simple and this video seems to want to imply something like this. And like others have said, this is most likely a correlation. However we measure intelligence, it will be more likely that those on the lower scale are more often controlled by organized religion. It is not a great discovery really. I would really like to have a look at those studies actually out of curiosity.

I don't think religion makes people stupid, but I do think that unscrupulous people can easily abuse religion to manipulate gullible people for their own purposes.

Intelligent people aren’t swayed by dogma; they question it and are perfectly capable of recognizing when someone selectively picks out certain Bible passages (etc.)—or even makes them up—to push some position that isn’t further substantiated.

Stupid people, unfortunately, are not capable of this, which is why they are susceptible to manipulation—even when a religiously “legitimized” position stands in complete contradiction to the religious doctrine on which it is supposedly based. The best example of this is the fundamentalist Christians in the U.S.: Here, religion often serves to “justify” inhumane positions, since they serve the interests of the super-rich.

However, this often happens in such an absurd contradiction to, for example, the Christian commandment of love for one’s neighbor that it should be very obvious to anyone who claims to be a Christian. Since that is often not the case, however, the only conclusion that can be drawn is that the people who nevertheless allow themselves to be influenced by this are not believers at all, but merely idiots who parrot whatever a completely secular, false prophet feeds them—they are thus incapable of thinking for themselves, which is precisely what makes them idiots, and which in most cases is probably what led them to that “religion” in the first place, or rather, to the cult whose goals they allow themselves to be exploited for, against their own interests.

So no, I don’t think religion inherently makes people stupid—only when it prevents people, as part of their socialization, from learning to think for themselves and to evaluate and weigh arguments. This certainly happens in areas heavily influenced by fundamentalism, but it is less a problem of religion as such than a problem of its abuse by unscrupulous opportunists who exploit it for their own personal gain.

Every world religion serves a function in organizing society and teaches values for peaceful coexistence. Fundamentalists, however, abuse it to artificially create “in” and “out” groups, which in turn helps them advance their political agenda. Therefore, we must draw a distinction and consistently expose those opportunists who are motivated solely by their own self-interest: these include all fundamentalist movements that use religion as a means of political power - I don't think there is anything religious about them, since their goal is always a political one.

Chicken or the egg?