Christopher Obal used to be a Christian. He grew up in Queens, New York, and when he was 5 years old, his parents left Catholicism for a very different form of Christianity. While they didn’t claim a specific denomination, he said the churches they went to would probably be described as Pentecostal, evangelical and charismatic.

“We attended churches where people spoke in tongues, and believed in the gifts of the spirit as well as a God who spoke to his people frequently,” he said.

As an adolescent Obal was obsessed with discovering God’s plan for his life and doing God’s will. At the age of 18, he attended Oral Roberts University, a conservative Christian college in Tulsa, Oklahoma. But while at college, he began to question his beliefs. Now, while he’s open to the possibility of “god, gods, goddesses, aliens, universal consciousness, or whatever,” he’s not affiliated with any religion. The rest of his family remains devoutly religious.

Obal is one of only a small percentage of Americans who grew up in religious households and are now religion-free. A 2008 report by the Pew Forum on Religion & Public Life found that only 12.7 percent of people raised in a particular faith eventually become unaffiliated with any religious group. Why did Obal abandon Christianity, while his friends and family remained faithful?

As with many things regarding human nature, the answer is complicated. But a good place to start is the nature of belief itself.

It’s no surprise that most Americans believe in God, according to science writer and skeptic Michael Shermer. In his book “The Believing Brain,” he explains how belief was beneficial to human evolution. He said that “the tendency to find patterns in both meaningful and meaningless noise” — or, as he calls it, “patternicity” — developed as a way to keep humans alive.

He gives the example of an early human hearing a “rustle in the grass.” Is it a hungry predator or is it the wind? If the person assumes it’s a hungry predator but it’s actually the wind, he or she will come to no harm. But if the person believes it’s the wind when it’s actually a hungry predator, it could mean death. So, the tendency to be overly cautious and falsely believe leads to being able to pass on those cautious, believing genes. Or, as Shermer puts it, “we are the descendants of those who were most successful at finding patterns.”

Shermer adds that once humans see the patterns, they tend to infuse them with “meaning, intention, and agency.” He calls this “agenticity.” How does this lead to supernatural belief?

“God is the ultimate pattern that explains everything that happens,” he wrote, “the ultimate intentional agent.”

Shermer cites studies that show a heavy “genetic influence on intentional belief.” And he says that “people who grow up in religious families and later become religious do so because they have inherited a disposition to resonate positively with religious sentiments.”

In the popular book “The God Gene,” American geneticist Dean Hamer proposed something similar. He said that “we have a genetic predisposition for spiritual belief that is expressed in response to, and shaped by, personal experience and the cultural environment.”

Belief was a positive development for the evolution of our species, and we haven’t evolved beyond it. According to a May Gallup poll, 86 percent of Americans believe in God. The question now becomes: Why doesn’t everyone believe in God?

Many researchers have asked this same question. Some studies suggest that a skeptical brain works differently than a believing brain. One example is a 2012 study titled “Is it Just a Brick Wall or a Sign From the Universe: An fMRI Study of Supernatural Believers and Skeptics.” In this experiment, the participants’ brain activity was monitored while they read a scenario, then looked at a picture. They were asked what thoughts that image would evoke if they were in that scenario, then saw that picture on a poster as they were walking down the street.

For example, imagine you just had a job interview. You walk down the street, and see a poster of a business suit. How would that make you feel? What does that poster mean? The supernaturally inclined were more likely to see it as a meaningful omen, a sign that they would get the job. The skeptics in the group did not see any significance in the image.

The researchers found that one region of the brain (the right inferior frontal gyrus) “was activated more strongly in skeptics than in supernatural believers.” The more active that part of the brain, the less likely participants were to find supernatural meaning in the images. The researchers think this is because the active region of the brain is associated with cognitive inhibition.

Cognitive inhibition is the mind’s ability to stop or override a certain mental process — the ability to stop unwanted thoughts, for example, or to weed out irrelevant information. One example of where cognitive inhibition is useful is in overcoming prejudice. If people want to avoid discriminating, they need to inhibit or suppress any negative stereotypes they might have toward a certain group of people.

For the people in the study, seeing a business suit in a poster was not logically connected to their chances of getting the job in any way. Still, supernatural believers found meaning there. They weren’t willing (or able) to suppress the thought that “this is a sign I will get the job.” The findings of this study supported the researchers’ hypothesis that “a skeptical attitude toward supernatural phenomena is associated with stronger cognitive inhibition.” And, as many skeptics formerly held supernatural beliefs, the researchers propose that “developmental increases in cognitive inhibition may be among the factors that contribute to the decline of these beliefs.”

It may have been just this that led Elizabeth Cady, a former evangelical Christian currently living in San Francisco, to her current agnosticism. When asked what it was that made her change her beliefs, she had a quick response.

“I had some gay friends in high school,” she said, “that got me into the questioning thing.”

Forming a positive relationship with people who were condemned by her religion required that she inhibit her religious belief that “homosexuality is bad.” This led her to question other beliefs as well. She wouldn’t be able to question those beliefs if she wasn’t able to suppress her church teachings in the first place.

British blogger Jonny Scaramanga had a similar experience. Scaramanga grew up in in a fundamentalist Christian household in England and is now an atheist. His journey to atheism began with listening to secular music and being surprised at how he felt.

“That music made me feel happier than Christian music ever had, which contradicted what I’d been taught,” he said. “It also made me comfortable with listening to ideas I didn’t agree with, and it made me feel like non-Christians weren’t so bad.”

This is another example of strong cognitive inhibition. He was able to suppress the belief that secular music was evil, and that led to his being able to entertain other ideas that conflicted with his religious beliefs.

Of course, one’s brain isn’t the only factor in whether or not someone is religious. The biggest factor in someone’s current religious belief is his or her parents’ religious belief. As noted earlier, Shermer thinks this is mainly because of an inherited genetic predisposition. But Vern L. Bengtson and Norella M. Putney, the authors of the book “Families and Faith: How Religion Is Passed Down Across Generations,” have a different, more sociological approach. They looked at the progression of religious faith from parents to children in order to figure out “what families should or should not do to be effective in sustaining religious continuity.”

Not surprisingly, the biggest factor in parents being able to successfully pass on their religion to their children was their relationship with their children. The authors found that “parents who interact with their children during their formative years in a warm, affirming and respectful manner are more likely to pass on their religious tradition, beliefs, and practices.” Other things that aid successful transmission include having parents of the same faith who do not divorce and having a strong relationship with grandparents of the same faith.

On the other hand, religious conflict between parents and children was one of the most common routes from religion to atheism. If resistant children were forced into religious activities, they often rebelled as soon as they had the chance.

So, a child with weak cognitive inhibition and a positive relationship with his married parents of the same faith is likely to carry on in the religious family tradition. A child with strong cognitive inhibition who is forced to go to church against his will is likely to rebel.

Was the latter the case with Obal? He shared his parents’ belief as a child, but his parents “bribed” him into going to Oral Roberts University, so there was some religious conflict. As for cognitive inhibition? Well, he did successfully inhibit his religious belief.

When asked what led to his change in beliefs, Obal has a long list of items that led to his disillusionment with religion. He worked at the Oral Roberts University Television station and said this experience led him to see that “this whole world of TV evangelism and [religious network] Trinity Broadcasting was just a scam.” Also, he saw many friends and family blindly support the war in Iraq after 9/11 and began to think they were influenced by propaganda instead of following God. This led him to question Christianity as a whole.

He gave some credit to a certain plant as well.

“I started using marijuana, which opened my mind,” he said. “So my thought process became a bit more critical towards religion and the implausible cornerstones of faith.”

Along with cognitive inhibition and familial transmission, this sounds like something that requires further research.