At last check, intimations of mortality had not been banished from the human mind—the Grim Reaper still stalks our thoughts. Nor have our brain circuits shaken their habit of perceiving patterns in chaos, such as seeing the face of Jesus in a piece of burned toast; imagining the invisible hand of a supernatural agent in acts of randomness, as in "answered" prayers; and conjuring what anthropologist Pascal Boyer of Washington University calls "non–physically present agents." We use the same circuitry to envision "what if" scenarios about our pasts or futures as we do to imagine angels and demons. Yet scientists have invoked both the fear of death and the fact that normal mental processes predispose us to belief in the supernatural to explain the near universality of religious faith down through the ages. (Of course, humans might believe in God because a deity designed that belief into our brains, but that hypothesis is not amenable to scientific investigation.) But there's nothing like facts to spoil a good story.

Before I get to the pesky new data, it's worth emphasizing that there are intriguing neurobiological findings suggesting that the brain may indeed be wired for God. In addition to the habits of thought that lead us to see the supernatural in the natural and the extraordinary in the ordinary, neuroimaging studies suggest that we come preloaded with the software for belief. For instance, the brain has a region, the parietal lobe, that detects where our body physically ends and the larger world begins. But this circuitry can be silenced by intense prayer or meditation, neuroscientist Andrew Newberg has found, producing a sense of oneness with the cosmos or God.

There is a common belief that if some trait or behavior is wired into the brain, it is unchangeable, inevitable. (The same goes for anything genetically based, but we'll leave that myth to another day.) Which makes the latest data on religiosity even more fascinating.

In brief, the number of American non-believers has doubled since 1990, a 2008 Pew survey found, and increased even more in some other advanced democracies. What's curious is not so much the overall decline of belief (which has caused the Vatican to lament the de-Christianization of Europe) as the pattern. In a paper last month in the online journal Evolutionary Psychology, Gregory Paul finds that countries with the lowest rates of social dysfunction—based on 25 measures, including rates of homicide, abortion, teen pregnancy, sexually transmitted disease, unemployment, and poverty—have become the most secular. Those with the most dysfunction, such as Portugal and the U.S., are the most religious, as measured by self-professed belief, church attendance, habits of prayer, and the like.

I'll leave to braver souls the question of whether religiosity leads to social dysfunction, as the new breed of public atheists contends. More interesting is the fact that if social progress can snuff out religious belief in millions of people, as Paul notes, then one must question "the idea that religiosity and belief in the supernatural is the default mode of the brain," he told me. As he wrote in his new paper, "The ease with which large populations abandon serious theism when conditions are sufficiently benign . . . refute[s] hypotheses that religious belief and practice are the normal, deeply set human mental state." He posits that, rather than being wired into the brain, religion is a way to cope with stress in a dysfunctional society—the opium-of-the-people argument.

This doesn't have to be an either-or proposition, however. The brain may indeed be predisposed to supernatural beliefs. But that predisposition may need environmental input to be fully realized.

Something like that seems to explain a number of animal behaviors that have long been thought of as innate. For instance, ducks are supposedly wired to prefer their mother's call and not, say, a goose's. But in the egg, ducklings hear the sounds of their mother, their embryonic siblings, and themselves; deprived of those experiences, they do not exhibit the "hard-wired" imprinting. Similarly, studies seem to show that fish have an innate sense of geometric direction. But if the fish do not first explore their tank, their sense of direction stinks, suggesting that they acquire it and are not born with it. "Researchers sometimes claim we're hard-wired for things, but when you peel through the layers of the experiments, the details matter and suddenly the evidence doesn't seem so compelling," says psychologist John Spencer of the University of Iowa.

Before we decide that a behavior is innate and wired into our neurons, it would be a good idea to examine whether it withstands changes in our circumstances. If the new neuroscience has taught us anything, it's that the lives we lead can reach into, and change, our very brain circuitry.

Begley is the author of Train Your Mind, Change Your Brain.

© 2009