“By doing so, the brain attempts to optimise the processing of the incoming
speech, ensuring more speedy and accurate responses.”

The study, entitled “Brain ‘Talks Over’ Boring Quotes”, was conducted by
scientists at the University of Glasgow's Institute of Neuroscience and
Psychology.

Researchers scanned the brains of 18 participants using functional magnetic
resonance imaging (fMRI) while they listened to audio clips of short stories
containing direct or indirect speech quotations.

The direct speech heard, for example when Mary said: “That film was terrible,
I’ve never been so bored in my life”, were spoken either “vividly” or
“monotonously”.

Changes to oxygen levels in the blood demonstrated that activity in areas of
the brain’s auditory cortex, which deals with human speech, increased when
people listened to monotonously-spoken direct speech quotes. Scientists
speculate that this is likely to reflect the existence of an inner voice.

Last year, research conducted by the same scientists found that the brain can
also create an inner voice when people read silently to themselves.

Professor Christopher Scheepers, a joint author of the study published in the
NeuroImage journal this month, said: “Direct speech quotations are generally
assumed to be more vivid and perceptually engaging than indirect speech
quotations as they are more frequently associated with depictions of voices,
facial expressions and co-speech gestures.

“When the brain does not receive actual stimulation of auditory speech during
silent reading, it tends to produce its own to enliven written direct speech
quotations - a phenomenon commonly referred to as the ‘inner voice’.

“Now it appears the brain does the same even when listening to
monotonously-spoken direct speech quotations.”