Inner Speech, Brain Circuits, and Voice Hearing: A Neuroscience Look at How We Talk to Ourselves

In this episode of Shortwave, NPR researchers talk with Durham University psychologist Charles Fernyhough about inner speech, the silent dialogue many people experience. The conversation explains how inner speech can be word-based for some and image- or emotion-based for others, and traces its developmental roots to private speech in childhood. The team dives into how brain networks—especially left-hemisphere language areas and a right-hemisphere region linked to understanding others—work together during internal conversations, and how elicited versus spontaneous inner speech produce different brain activation patterns in MRI studies. The discussion also covers voice hearing, its relation to inner speech, and why some voices feel external. The episode closes with practical resources for understanding voice hearing and the diversity of human minds.

Overview: Inner speech and its variety

The episode centers on inner speech, the internal conversation many of us have with ourselves, and how it starts from private speech in early development. Charles Fernyhough explains that inner speech can be word-based for some and image- or emotion-based for others, underscoring the diversity of mental experiences. He notes that inner speech stems from social dialogues with caregivers and peers that become internal conversations, a theory rooted in the work of Russian psychologist Lev Vygotsky.

"private speech... it's the precursor. It's the thing that comes before inner speech" - Charles Fernyhough

Brain networks: language and social cognition

The discussion moves to brain systems, highlighting left-hemisphere language regions such as Broca's and Wernicke's areas and a right-hemisphere region involved in representing other minds. Fernyhough and the researchers show that inner speech activates a dynamic loop between language networks and social-cognition regions, reflecting that inner dialogues may involve more than straightforward speech production.

"it's important, but it's not the whole story" - Charles Fernyhough

Elicited vs spontaneous inner speech: what MRI reveals

Realtime brain imaging reveals differences: when inner speech is elicited by a task, Broca's area shows strong activation; spontaneous inner speech relies more on posterior regions and areas tied to social interpretation. The researchers remind us that scanning may not perfectly reflect natural inner experiences, urging caution in interpreting MRI results as direct windows into inner life.

"elicited inner speech... there was lots of that Brocas area, but spontaneous inner speech showed more Wernecker activity" - Charles Fernyhough

Voice hearing and inner speech

The episode explains voice hearing as the experience of hearing voices without an external speaker, often linked to inner speech when the brain misattributes self-generated thoughts to another source. The neural model involves disruption in the internal monitoring signal that ordinarily helps distinguish self from other voices, shedding light on why some people hear voices under different circumstances.

"what's actually happening is that they're producing some inner speech" - Charles Fernyhough

Diversity, support, and further learning

The discussion emphasizes celebrating the diversity of human minds and acknowledges that inner speech can have both positive and negative mental-health implications. Fernyhough points listeners to Understanding Voices.com for broader information about voice hearing, treatment options, and personal coping strategies.

"I celebrate the diversity of human minds" - Charles Fernyhough