It has happened to me only twice. Each time, only a single word was spoken. But the impact of hearing someone who isn’t there speak to you is profoundly unsettling, even if it is only single word. I can’t begin to imagine what it would be like to have this kind of thing happening to me constantly, unrelentingly.

People who say they frequently hear voices from nonexistent people talking to them from outside their head say this takes away peace of mind, self-confidence and any semblance of a “normal” life. It causes them to withdraw from a world that simply doesn’t understand what is happening to them or why—and, of course, they don’t know why it’s happening to them either. Only that it involves years and years of hearing disembodied, “outside the head” voices, sometimes for hours daily—and sometimes multiple voices, each with its own distinctive vocal characteristics. It surely must be like, and those who experience it, say that it is, a severe pain for which there is no alleviation and which can literally rob you of your health and sometimes your sanity.

Both of my experiences involved children whom I love dearly.

One morning in the mid-70s I was working at home when I suddenly heard my second-grade daughter shout, “Daddy!” I erupted in goose bumps, thought about it for a moment and then ran, not walked, to my car. Her school was three blocks away, and I was there in less than a minute. Not until I could look through a window in her classroom door and actually see her peaceful and safe could I begin to shake off the effects of my auditory hallucination.

The second experience was much more recent. One night last year, shortly after switching off the light in my motel room in Oklahoma City, I heard my three-year-old grandson call out, “Pappaw!” Lunging for the lamp switch, I could immediately see that I was still the room’s only occupant. And I knew that this grandchild was 1,100 miles away. Did he need me? Remembering the previous incident, I decided not. But once again, it took a while for my heartbeat to calm.

We’ve been hearing a lot lately about such auditory hallucinations. The main reason is the release last month of Daniel B. Smith’s book, Muses, Madmen, and Prophets: Rethinking the History, Science, and Meaning of Auditory Hallucination.

Here’s some revealing insights on hearing voices from his book, from an interview with him by the Boston NPR station WBUR and from other sources:

• A lot of people hear voices from outside their heads. Smith estimates those who have had vivid auditory hallucinations at from 3 to 5 percent. One survey reported 39 percent of so-called healthy folks had heard their own thoughts aloud. Smith told WBUR’s Tom Ashbrook, “It’s hard to say but I would guess that it’s a lot more common than people recognize or realize or perhaps want to think.”

• While the brain science on this subject “is actually not very advanced,” Smith says there’s already some very intriguing stuff. For example, one study suggests hallucinators may be processing words on the wrong side of the brain. Brain scans show schizophrenic patients activating language-massaging areas of the right brain when reading whereas non-voice-hearing persons use the left brain for such a task. This, researchers speculate, could cause hallucinators to generate speech they don’t associate with themselves.

• There is a huge benefit to those who frequently experience auditory hallucinations in taking this whole subject out of the shadows. In believing that people who hear voices really do. Letting them know you believe them. And letting them talk about what it’s like. Much of the credit for removing the stigma, mystery and avoidance long associated with such hallucinations goes to the founders of the Hearing Voices Movement. They are a Dutch psychology professor, Marius Romme, and a science journalist, Sandra Escher. In the early 90s, Romme was challenged by a patient, Patsy Haig, to believe the voices causing her such distress were real. The pair went on a TV chat show and the shows was flooded with callers saying, “Me, too!”

• Evidence grows that hearing the voices is often a consequence of psychological trauma. A divorce, an accident, a pregnancy, the death of a spouse, and much too often, emotional and/or physical abuse. Romme and Escher developed a method called “Making sense of voices.” Some hallucinators benefit from drug treatments, others from having magnetic fields aimed at parts of their brains. But a great many benefit simply from listening to others talk about how they took control of the voices. A British rugby player told listeners to an Australian radio show, “All in the Mind,” how he came to realize his six (soon to be seven) voices were real, not imaginary as he’d been told. He then realized that “this experience is real so you have to do something about it, there’s no point waiting for other people to do something for you.” He took control of his voices, married, had children, “got on with my life.”

• What about all those often influential people in history, especially in religion, who claimed to have heard the voice of God? As occupants of a scientific age, should we assume that, as Smith puts it, antipsychotic medication might have helped Moses understand that God’s speaking to him from the burning bush as actually “his dopamine system playing tricks on him”? Smith isn’t sure. Questions of faith remain tricky. For certain, the new evidence on auditory hallucinations complicates the debate over “religious inspiration.” From one point of view, the controversial bicameral hypothesis of the late psychologist Julian Jaynes—that one side of the brain appears to be speaking and the other side listens and obeys—is looking better and better as our knowledge of the brain increases. Jaynes argued that this was normal for humans as recently as 3,000 years ago. In taking auditory hallucination out of the shadows, we are now seeing that it is still all-too-normal for many people 3,000 years later.

I know it can happen because, as I said, on a very small scale, it has happened to me twice.

To order Smith’s book, go here: Muses, Madmen, and Prophets: Rethinking the History, Science, and Meaning of Auditory Hallucination

For WBUR’s interview with Smith, go here: Tom Ashbrooks’ Hearing Voices interview

For information on the Hearing Voices movement, go here: Hearing Voices Movement

For the Australian Broadcasting Company’s program, go here: Hearing Voices: The Invisible Intruder

For information about Julian Jaynes, go here: Julian Jaynes Society