It's a touchy, controversial question: Are religious experiences real, or are they nothing more than the result of neurons firing and misfiring, natural processes interpreted as divine intervention?
A new series on the National Geographic Channel aims to explore that question with advanced research about religion and the brain. Titled "Brain Games: The God Brain," the program is slated to begin on Feb. 21 at 9 p.m. EST.
The question has spawned an entirely separate field of study known as neurotheology.
One way scientists study the intersection of faith and brain chemistry is by monitoring the brain itself during religious experiences. Using common medical scanning technology -- like functioning MRI, or fMRI, EEG, and PET scans -- scientists study the blood flow and neural activity in the brain as people pray, discuss religion, or experience what they believe are interactions with God.
Those studies have consistently shown that certain areas of the brain light up in response to religious experience, as Brain Blogger notes. MRI scans show activity in the hypothalamus, amygdala, and hippocampus when study subjects engage in activities like meditation, according to the Psychiatric Times. Neurotheologists support their claims that the brain is hardwired for religion by pointing out that scans show the brain undergoes measurable changes during prayer and meditation, the same way emotions like happiness, depression and sadness produce measurable differences in brain scans.
To some, those results are evidence that spirituality is a matter of perception, and that things like belief in God or religious experiences are entirely contained within the brain, determined by its chemistry.
Others take a different view. Take, for instance, the words of Ilia Delio, a Franciscan nun with doctorates in pharmacology and historical theology:
"It is tempting to speculate that there is a 'God module' in the brain and that such a module is located in the area of the limbic system; however, such speculation needs to be made cautiously. What these findings do point to, however, is that spirituality involves the brain. For the first time in human history we are beginning to understand spiritual experience not as something apart from the physical human but rather bound up with human matter, that is, the matter of the brain. Thus, matter and spirit are no longer seen to be opposed but are indeed mutually related, if not one and the same."
The "neuroscientific study of religious and spiritual phenomena remains in its infancy," Brain Blogger notes, pointing to studies that only scratch the surface of questions about religion and brain chemistry.
Other research tackles those questions from different angles: For instance, studies have shown that children who are not taught about religion will develop their own notions of God or a creator figure, while others seek to explain historical accounts of spiritual apparitions by diagnosing saints and historical figures centuries removed. That's led some scientists to conclude that psychiatric diseases can account for at least some of the stories about people who say they've spoken to God, or who have undergone dramatic religious conversions.
"For them it's the spirit of God which is moving through them," neurotheologist Dr. Andrew Newberg told BigThink. "I can't prove that or disprove that on the basis of a brain scan, but I can see the changes that are going on in the brain while they're engaged in this very, very powerful and very deep spiritual practice... It certainly looks like the way the brain is put together makes it very easy for human beings to have religious and spiritual experiences."