This woman, however, said that she had been to a job interview and that later, while tidying up at home, she had heard God say, “That’s not the one” — and that she had looked around to see where the voice had come from. She told me that she heard from God like that many times. The first time as an adult was when she was driving alone in an unfamiliar part of the city — and God spoke up audibly out of the back seat and told her that he would always be with her.

After that, I started to ask people in the church more systematically about whether they had ever heard God speak audibly. About a third said yes. They reported odd auditory events in which God said “Sit and listen” or “Read James” or “I will always love you.”

This woman’s account is a good example: “The Lord spoke to me clearly in April, like May or April. To start a school.”

You heard this audibly, I asked? “Yeah.”

Were you alone? “Yeah, I was just praying. I wasn’t praying anything, really, just thinking about God, and I heard a voice say, ‘Start a school,’ I immediately got up and it was like, ‘O.K., Lord, where?’ ”

What do we make of this? I don’t think that anthropologists can pronounce on whether God exists or not, but I am averse to the idea that God is the full explanation here. For one thing, many of these voices are mundane. A woman told me that she heard God tell her to get off the bus when she was immersed in a book and about to miss her stop. Moreover, odd auditory experiences are quite common. A questionnaire posed to 375 college students found that 71 percent reported vocal hallucinations of some kind, according to a study published in 1984 (a finding consistent with my own research). A 2000 study found that 38.7 percent of the population reported visual, auditory or other hallucinations, including out-of-body experiences.

Schizophrenia, or the radical break with reality we identify as serious mental illness, is also not an explanation. The people who reported these events simply weren’t ill in that way, and schizophrenia is not common (the prevalence among American adults is 1.1 percent in any year). Moreover, the patterns of their voice-hearing are quite unlike the patterns we associate with schizophrenia. The voices heard by people with schizophrenia are often harsh and commanding. They go on and on — sentences, paragraphs, sometimes crowds of people screaming and yelling insults at the poor voice-hearing person throughout the day.

The unusual auditory experiences reported by congregants just weren’t like that. They were rare. Most people said they’d had one or two in their lifetime. They were brief — just a few words. They were pleasant. And they did not have that sense of command. The woman who said God instructed her to start a school — well, she hasn’t done it.

I eventually discovered that these experiences were associated with intense prayer practice. They felt spontaneous, but people who liked to get absorbed in their imaginations were more likely to experience them. Those were the people who were more likely to love to pray, and the “prayer warriors” who prayed for long periods were likely to report even more of them.

The prayer warriors said that as they became immersed in prayer, their senses became more acute. Smells seemed richer, colors more vibrant. Their inner sensory worlds grew more vivid and more detailed, and their thoughts and images sometimes seemed as if they were external to the mind. Later, I was able to demonstrate experimentally that prayer practice did lead to more vivid inner images and more hallucination-like events.

There’s plenty here to alarm secular liberals. A subject in the prayer experiment recalled that she was watching TV when “God told me, ‘Vote for Bush.’ I said — I was having this argument with God. I said out loud, I said, ‘But I don’t like him.’ You know. And God said, ‘I didn’t ask you to like him.’ ” She thought she had heard this exchange with her ears. She voted, in 1988, for George Bush.

The more interesting lesson is what it tells us about the mind and prayer. If hearing a voice is associated with focused attention to the inner senses — hearing with the mind’s ear, seeing with the mind’s eye — it suggests that prayer (which today, the National Day of Prayer, celebrates) is a pretty powerful instrument. We often imagine prayer as a practice that affects the content of what we think about — our moral aspirations, or our contrition. It’s probably more accurate to understand prayer as a skill that changes how we use our minds.

T. M. Luhrmann, a professor of anthropology at Stanford and the author of “When God Talks Back: Understanding the American Evangelical Relationship With God,” is a guest columnist.