¡°Do you hear voices talking to you as I am now?¡± Psychiatrists have been known to ask this of patients in the belief that talking to oneself is the first sign of madness. But is this maxim true? After all, talking to oneself frequently plays a role in our achievements as both children and adults.

For psychologist and novelist Charles Fernyhough, some telling examples include his two-year-old daughter saying to herself as she plays with her toys: ¡°I¡¯m going to make a train track and put some cars on it.¡± He celebrates his own achievement in telling himself a sentence from a short story he is writing that amuses him so much he laughs out loud.

Other instances he cites include the tennis champion Andy Murray ordering himself how to play his next game, Van Gogh planning a picture, and Virginia Woolf talking aloud as she tried out sentences before writing them. To this Fernyhough adds Christopher Isherwood recording a duologue that ran ¡°Couldn¡¯t you get yourself excited by the shape of girls, too ¨C if you worked hard at it?¡±, the retort ¡°Why the hell should I?¡±, and finally ¡°Well, it would be a lot more convenient for you if you did.¡±

Today¡¯s psychologists are suspicious of the value of reports such as these, based as they are on after-the-fact introspection. Fernyhough solves this problem by getting those he studies to carry an audio recorder and to respond, whenever the device¡¯s beeper randomly sounds, by saying what is in their mind at that very moment. Sometimes, although by no means always, they respond with inner speech. One subject, Lara, is a case in point. She says that at one point when the beep sounded, she was putting down a bottle of beer and thinking, ¡°Do I want another one?¡±

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What brain processes occur in such inner speech? One possibility is that the cortical system involved sends a signal to the brain¡¯s speech detection area, telling the speaker, ¡°This is you speaking.¡± By contrast, according to this hypothesis, auditory hallucinations occur when such a signal is not given to the brain¡¯s speech detection or ¡°listening¡± area, with the result that inner speech is experienced as a voice coming from outside.

This might have been what happened when the 15th-century Norfolk mystic Margery Kempe heard Christ talking to her. It may also happen in ¡°voice-hearers¡± today, who, thanks to the work of the Dutch psychiatrist Marius Romme, Fernyhough understands as victims of trauma. As illustration he recounts the case of Eleanor Longden, a woman who, having been subjected as a young child to ¡°horrific and organised sexual torture¡±, suffered as a student with auditory hallucinations in which she heard voices commenting on her, saying things such as ¡°She is leaving the building¡± and ¡°She is opening the door¡±.

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Freud attributed such hallucinatory experiences to dissociation and projection on to the external world of superego figures in the mind that were first formed through internalising the experience of those who look after us as infants. Fernyhough mentions Freud, and he also mentions Longden¡¯s childhood experiences. But he says nothing more generally about the ways early and subsequent interpersonal factors fuel the ¡°chorus¡± of voices shaping inner speech and auditory hallucinations. Nevertheless, and despite occasionally bland and tedious passages, his book, with its extensive illustrations of the creative effects of inner speech and voice-hearing, sane and mad, is a thought-provoking and engaging read.

Janet Sayers is emeritus professor of psychoanalytic psychology, University of Kent.

The Voices Within: The History and Science of How We Talk to Ourselves
By Charles Fernyhough
Profile Books, 352pp, ?16.99 and ?14.99
ISBN 9781781252796 and 2830788 (e-book)
Published 21 April 2016