Children will often have imaginary friends, the recently bereaved sometimes hear their loved ones and for some people voices in their head can be a horrible, destabilising ordeal.
The full gamut of experiences are to be explored in detail at this year's Edinburgh International Book Festival, in a project investigating why and how people hear voices when no one is speaking.
Researchers from Durham University's Hearing the Voice project will be at the festival asking both readers and writers what their experiences are. There will also be interviews, panel discussions and workshops delving into what is still a little-talked-about subject.
The project's director, Charles Fernyhough, said: "It is usually considered a troubling symptom of a severe mental illness but is more and more being recognised as something that happens to a lot of people and there are a lot of different contexts."
That's not to say it can be very troubling and destabilising, he added, and that most people would be worried if they started hearing voices.
"There's a terrible stigma about it," he said. "It is something many people who have the experience feel very uncomfortable talking about because they fear the reaction of society, for good reason."
Having the opportunity to talk to a "captive audience" of writers will be invaluable, said Fernyhough. "They often have to hear the voices of their characters before they can write."
Similarly, for readers, hearing the voices of the people they are reading about is an important part of the process.
The research project will ask questions around the very common hearing voices of a loved one after they have died; children and their imaginary friends; and hearing the voice of God.
There are a number of Conservations with Ourselves events, including a panel discussion with novelists Matthew Quick, Edward Carey and Nathan Filer, whose novel The Shock of the Fall, about a young schizophrenic man who struggles with guilt after the death of his brother, won the 2014 Costa book award.
Fernyhough said people should not automatically fear the worst if they hear voices, but added: "It is very important not to go too far. Yes it can be normal in certain contexts, but many many people are really troubled by the experience and the voices say horrible things."
He added: "It is about breaking down the stereotypes, breaking the knee-jerk connections to serious mental illness. Above all if there is a message to people it is: don't suffer in silence."
Contributors to the project, ranging from novelists to medical researchers, will blog about what hearing voices means to them throughout the festival. To take part in the study, fill in the questionnaire on the Inner Voices website.