Researchers at the University of Glasgow say the phenomenon has long been accepted but never scientifically investigated.
"Although many of us share the intuition of an 'inner voice,' particularly during silent reading of direct speech statements in text, there has been little direct empirical confirmation of this experience so far," researcher Christoph Scheepers said.
Now scientists at the university's Center for Cognitive Neuroimaging have established that reading direct speech activates "voice-selective areas" of the brain, a university release reported Tuesday.
Scheepers and his team scanned the brains of 16 participants in the study using functional magnetic resonance imaging while they read different short stories.
Direct quotes activated voice-selective areas of the brain's auditory cortex, MRI results showed.
"This reveals that readers are more likely to engage in perceptual simulations, or spontaneous imagery, of the reported speaker's voice when reading direct speech," Sheepers said.