I suppose such a study glosses over people like Isaac Newton, Leonhard Euler, Abraham Lincoln, Albert Einstein, Werner von Braun, John Glenn, Michael Behe and others like them who were and are of exceptional intelligence and retained a lifelong belief in God. Some of these people were not conventionally religious in that they did not attend a church or otherwise were members of an organized religion. Nevertheless, their belief and faith in God never wavered.
Speaking on a personal note, I am also a believer and always have been. I like to think that since I possess two college degrees (one in mathematics) and am involved in public education, I would be considered to have above average intelligence. Similarly, I have met other people during my education, which includes studying at three universities, who were also believers. Some were students like me and others were faculty members.
If you want to believe that religious people are stupid, you can certainly find all kinds of data to support such a conclusion. Also, one can look through history and see the many horrible things religious people have done. But I think it is equally important to point out that those of high intelligence have also committed atrocities against humanity. Their learning did not stop them from formulating weapons of mass destruction, drawing up plans for genocide, swindling governments, societies and individuals and other crimes. This study reminds me of the old saying, “When you point a finger at somebody, it is good to remember you have three more pointing back at you.” Those eager to impugn believers would do well to remember this.
Quendi