Studies have shown that atheists are more intelligent than theists. I think it's by default because theists may be philosophically challenged to embrace certain concepts, like Big Bang cosmology or evolutionary biology. Atheists, however, are not limited by these dogmas. That said, it needs to be mentioned that many of the greatest discoveries throughout history have been made or confirmed by theists.
And since you put "atheistS" and "theistS" meaning the groups as a whole and not individuals. No individual trait can be discerned from their grouping in such a manner- simply knowing a person is an atheist and knowing another person is a theist tells you nothing about that individual. But since you used the plural, I'm assuming you meant to deal with the groups as a whole.
It is a statistical fact that atheists have a higher average IQ than theists. It is a statistical fact that atheists have a higher average education level than theists. It is a statistical fact that developed nations with high-scoring students and high levels of education have low religiosity.
HOWEVER- correlation does not equal causation. It is unlikely that atheism directly is the CAUSE of the higher intelligence. Atheism is more likely a byproduct. People who have higher education are more likely to exhibit critical thinking skills, and critical thinkers are more likely to (a) question concepts they have been taught are true and (b) be less superstitious than their peers. This leads to a higher incidence of atheism in these groups.
But since you said on another comment that you posted this just so you could yell at anyone who said "yes", you apparently aren't interested in the rational reasoning.
Atheists look to facts, not scripture, for guidance. While plenty of theists are smart and some even brilliant, intelligence is not a requirement to be religious. Anyone can be brainwashed into believing the bible. Atheism, on the other hand, requires a questioning, curious mind that is willing to accept hard truths based on logic.
I don't believe one is smarter than the other but I feel people that believe in science have a higher potential for intelligence because religion can be a blinder and a lot of people who believe in religion have a "it's this way because it is" mannerism. Or with a video this girl put up the other day where she doesn't think dogs have brains because they don't like her so she assumes that God didn't create them because they can't talk.... It's literally as ridiculous as it sounds.
But intelligence is also relative but I feel religious people have a boundary line that atheists can cross.
Studies have proven that, on average, atheists tend to be more intelligent than theists. However, just because one is an atheist, doesn't mean they are automatically more intelligent than someone who is religious. There is a direct correlation between atheism/agnosticism and critical thinking, using and determining logic, decision making and higher intelligence. This is what the studies say, and based on personal experience, I have met more intelligent atheists and non-religious than I have religious.
We tend to overthink or underthink everything. I broke my arm a few months ago because of a broken board in a loft ceiling. It ended up getting around and back to me that I had fallen through a roof on purpose. Why? Because each time the story was told it had just one little detail changed. That happened in three months. Now, translate hundreds of stories hundreds of times from language to language for 2000+ years and see how misconstrued it gets. How come atheists think of this stuff? Because they're allowed to. In Christianity the very definition of "evil" is an angel who dared to rebel and dared to think he was capable of being greater than he was. He was cast out for ever even thinking of defying any authority, and then they claim that no one has the power to create other than God. By definition, inventors and free thinkers align with Satan. Here's the crazy thing: All the people who say these things about how Satan is evil and that whole "left-handed people are evil because they're creative and God is the only creator" are saying those things on the internet. So, I'm going to go on a limb here and assume the internet was created by an innovative person or group of people with huge aspirations to do great things. Literally, even arguing on the internet as a Christian is hypocrisy.
Atheists are more scientific while theists just make decisions according to a holy book which seems like a book of answers than may be wrong. Atheists need the evidence and they actually uses their brain and think, and that makes them smarter, also, studies found that most scientists are atheists. In addition, many atheist debators have a strong background in science, or is a scientist.
I think that atheists are generally smarter when it comes to the analytical side of things, because most of us atheists don't believe in god because there is no evidence. We are the type of people that are particular when it comes to providing evidence.
But this is only one side of the story. Theists are as good, maybe even better than atheists when it comes to creativity. Theists have the type of mind that is open to ideas and information that atheists simply don't agree with. So yes, atheists are smarter at things like maths, but theists are more creative with story writing.
When someone accepts a theistic claim and chooses not to learn about the contradictions science has shown, that's when you can find a correlation between Atheism and Intelligence.
Atheism does not hold back on learning about how things work because there's no personal beliefs getting in the way of knowing things. If there's new evidence in science or a new theory that states how there's more then what a religious claim can explain, theists tend to reject what science tells us instead of rejecting their beliefs in order to know what is true.
Then you have studies:
Overall, while it does not speak for any individual, studies have consistently shown a negative correlation between belief in a god and intelligence. In the end, it's not to say that believers have no credibility, most of them do, but statistically, it's true that the average atheist is smarter than the average theist.
I wont go much further than to say many of our greatest scientists have at least acknowledged that there is something greater than us out there. Also most of the world is some kind of theist and believes in something larger than themselves. One God one People. I am sorry to all those atheists who saw a PBS or BBC special, in reality you are probably agnostic. This transcends Christianity.
The word "smart" is subjective. You can be smart in religion, in which, obviously, a theist would be smarter than an atheist, or you could be smart in academics. People often find their way during their life as they go through experiences; you that began an atheist may become a theist and vice versa. If one was to make this switch, it does not make them smarter, it just changes their faith, or lack thereof.
The only difference between atheists and theists is that atheists believe that the universe and all its phenomena came into being be pure chance, whereas theists believe that it had some help from a divine consciousness which permeates throughout the universe. I am aware that atheists put a lot of thought into it before they make their choice to stop believing in God. However, theists also have a basis for their faith. They have spiritual experiences in which they can feel God's grace and love, thus confirming his existence. Theists aren't just blindly accepting whatever they're told, as many atheists seem to believe.
Really stupid thing to even ask. Of course not! How does believing in a God/higher being than oneself make you any less clever than someone who does not? Belief and religion, in my opinion, is completely separate from intelligence. Once toy begin mixing the two together, you get all kinds of issues that don't even need to be talked about.
Honestly, I find this whole idea dumb. There are plenty of dumb atheists as well who do very foolish and stupid things. So atheism has nothing to do with intelligence. So, no intelligence is not determined by what religion you belong to or any of that. It's determined by your faith.
All absolute answers are wrong on this matter. I am an atheist and I know many stupid theists, but I can not claim to be smarter than Descartes, Kant, Aristotle. The question itself is flawed. If you want an answer, take a huge random amount on atheists, a huge random amount of theists, let them sit for an IQ test and there you go: You'll have the answer of who's smarter in this particular time of history.
Your religion,mor lack of does not termite your intelligence. I'm Christian who have met many people of different religions and beliefs, including atheist. I have known smart Christians, dumb Christians, and everything in between. I have some at guest friends who I would consider very intelligent. It is the person's education and willingness to open their minds to new ideas that makes a person intelligent.
A 33 year old Christian may have the same intelligence as a 33 year old theist. A religion, or a lack of one does not make you smarter. A smart Christian may even be smarter than most Atheists, and a atheist may be much smarter than a intelligent christian so religion does not matter.
What I want to know is who posed this question. You can't actually be serious. Is an Atheist smarter than a theist? Of course! Just kidding. Leaving any religion out of this, have you seen some of the people walking around your neighborhood? Tried to get down an isle in the grocery store, and some moron is in the way. Now I ask, did you stop and ask if they were theist or atheist? No, of course not. That person just didn't need to exist!
Some athiests have the wrong idea that theists just blindly and unthinkingly follow religion. Nothing could be further from the truth. Most theist choose religion after much study, research and inner debate. No adult just accepts it without going through a research and study to find answers. It's got nothing to do with intelligence.