One of the most important facts to grasp about the small, but growing, flock of Americans who call themselves unbelievers is that most of them are converts. "When you meet people who identify themselves as 'atheists' or 'agnostics,' these are people who are taking a stand, they're committing themselves to a strong stance in this culture," said Greg Smith, senior researcher with the Pew Forum on Religion & Public Life. "People just don't wind up in the atheists-and-agnostics camp. They are there for a reason."

While some came of age in atheistic homes, the vast majority of atheists -- four out of five in one survey -- were raised as Baptists, Catholics, Jews or in some other faith, he said. Then they changed their minds, usually after intensely personal experiences, years of reading or both.

"When you say you're an 'atheist' that usually means that you've made a choice," said Smith.

This is a crucial fact to remember when reading news reports about the recent "U.S. Religious Knowledge Survey" released by the Pew Research Center.

While the New York Times headline calmly stated, "Basic Religion Test Stumps Many Americans," the Los Angeles Times was more typical of the national norm, offering a zinger that said, "If you want to know about God, you might want to talk to an atheist." USA Today proclaimed, "Unbelievers aced out the faithful when it comes to religious knowledge."

In this survey, 3,412 Americans -- 18 years old and up -- were asked 32 questions about the Bible, Christianity, other world religions and America's laws that govern faith and public life. Jews, Mormons, atheists and agnostics were "oversampled to allow analysis of these relatively small groups."

Overall, atheists and agnostics -- who were grouped together -- answered an average of 20.9 out of 32 questions correctly. The score for Jews was 20.5 and members of the Church of Jesus Christ of Latter-day Saints scored 20.3. There was a sizable gap, at that point, before reaching white evangelical Protestants, who scored 17.6, and white Catholics, who scored 16.0. Members of liberal Protestant churches scored 15.8.

The survey found that atheists and agnostics knew the most when asked about the beliefs of world religions. Mormons and evangelicals knew the most about the Bible and fine details of Christian beliefs.

Those who dug deeper found other complex dynamics at work, noted Smith. For example, while many noted that atheists and agnostics scored well, few commentators noticed the low score -- 15.2 -- earned by the much larger group of participants who choose the "nothing in particular" option when describing their beliefs.

This finding is significant in an age in which the number of Americans who describe themselves as "spiritual, but not religious" continues to rise. Some of the "nothing in particular" Americans are quite secular, said Smith, but others have their own "beliefs and religious practices that they say are quite important to them."

At the same time, it's important that believers who reported attending religious services once or more a week had higher levels of knowledge than those who attended less often. These scores rose higher when believers reported that they frequently read scripture, educational websites and books about religion. Believers who practiced their faith more often were also more likely to discuss religious issues with other people, further raising their scores.

The bottom line: People who hold strong beliefs about faith -- positive or negative beliefs -- seem to know more about religion than those who are less committed. Passion, not apathy, is what leads to knowledge.

Consider, for example, this crucial Catholic question. In one of the Pew survey's most surprising findings, 45 percent of the Catholics polled did not know that their church teaches that the bread and wine consecrated during the Mass are not merely symbols, but are believed to truly become the body and blood of Jesus Christ. However, nearly 70 percent of white Catholics who attended Mass once a week answered that question correctly.

"We already knew that Catholics who attend Mass every week act differently and even vote differently than other Catholics," said Smith. "What this survey shows is that Catholics who are more active in their faith think differently than other Catholics, too. ... Of course, it isn't surprising that people who enthusiastically practice their faith also know more about their faith, and even religion in general, than those who do not."