Terry is citing references used before on this site. These studies suggest correlations, sometimes strong correlations between theism and (lower) intelligence, for example, or a lack of belief in evolution/science and (lower) intelligence in this example.
The studies never suggest direct correlations (cause/effect), because there isn't a direct correlation. As such, they are accurate. Of course there are intelligent theists and bible believers. But the only thing required for Faith is Feelings, and religious people often suffer from the very worst confirmation bias, as their leaders dictate to them what they can read/consider. Just like the Catholic church did for centuries and the Dark Lords have for a century. Sound familiar? The leaders know that when people begin using their entire intellect, the bible and theism will suffer. There isn't much expansion of the brain cells when all you 'study' is confirmationally biased tripe and the primary fuel for your engine and how and when you make decisions is emotions (e.g., Fisherman).
It's like one of my old college profs said, a man with a doctorate in divinity, the only place belief in god is in short supply is a seminary. Caleb's culture is different, so much so that it is likely anomalous to studies such as these.
This isn't rocket science.