Inner Voice imageHearing the Voice was pleased to see coverage of Ben Alderson-Day and Charles Fernyhough‘s article ‘Inner Speech: Development, cognitive functions, phenomenology and neurobiology’ (Psychological Bulletin, September 2015) in a recent blog by Romeo Vitelli on Psychology Today.

Romeo Vitelli writes:

During every waking moment, we carry on an inner dialogue.  Whether you call it inner speech, self-talk, internal dialogue, or thinking to yourself, it seems to be an important part of our daily life.  Even though most of these inner dialogues stay well-hidden (except for the occasionally embarrassing moment), inner speech is far more important than most people realize.  From early childhood onward, inner speech plays a vital role in regulating how we think and behave.  Not only does it often allow us to “rehearse” different scenarios and enable us to avoid rash actions … [but it can also] shape how we see the world around us.

new review article published in Psychological Bulletin explores inner speech and how it can change and develop across our life span.  Written by Ben Alderson-Day and Charles Fernyhough of Durham University,  the article reviews existing research on inner speech and what makes it so important.   As they point out, we often have different definitions of what we mean by inner speech and even refer to it by many different names. Research studies looking at inner speech may refer to it by other names such as private speech, self-talk, covert speech, and auditory verbal imagery, etc.   For that matter, researchers have also looked at externalized self-talk, i.e., talking to yourself, which can be considered a form of inner speech as well.

But why is inner speech so common? According to psychologist Lev Vygotsky, our capacity for inner speech begins around the age of three as we learn to integrate the separate systems for thought and language.  As one example, Vygotsky described what he referred to as private speech in which children talk to themselves while carrying out a difficult cognitive task.   He suggested that this kind of private speech became more internalized as children grew older and become more capable of working on their own without help from a caregiver.

This evolution from private speech to inner speech seems to be a universal and very natural part of normal development.  Vygotsky and his supporters also suggested that inner speech can involve either expanded inner speech, which is basically the same as regular speech, and condensed inner speech which is closer to “thinking in pure meaning.” Charles Fernyhough suggests that inner speech is most likely to be condensed by default and we only switch to expanded inner speech when we are stressed or otherwise preoccupied with a problem. For this reason, inner speech plays an important role in self-awareness and self-understanding.
Inner speech may play an important role in working memory as well. Often confused with short-term memory, working memory refers to the transient storage of information such as a telephone number or the items in a shopping list.   Since we can only hold five to nine items in our working memory at any given time, we need to rely on various memory strategies to keep that information from decaying too rapidly. One approach that appears to work quite well with verbal material involves mentally rehearsing the information, including repeating it using either inner speech or saying the information out loud.  This also means that anything that interrupts this repetition process causes the memory to fade quickly.  Researchers suggest that children begin relying on repetition to boost memory as early as seven years of age or younger as language skills develop.


Though studying inner speech is often difficult for researchers (it’s inner speech, after all), the role it plays in different cognitive abilities, including memory and executive functioning seems well-established.  In children, for example, their cognitive abilities appear to grow and develop in much the same way that their ability to use inner speech does.  This suggests that inner speech is linked to the development of language abilities and the advanced mental abilities to which language is linked.  Inner speech also seems to be especially important in multi-tasking that involves “switching” between different ways of responding. For example, experiments that require people to switch between different arithmetic problems indicate that inner speech helps prepare them for making this kind of transition.

Another skill that appears linked to inner speech is silent reading. While children learning to read often need to read aloud or even move their lips as they follow that they are reading,  how well adults can follow what they are reading seems to be directly related to their skill at inner speech. The more difficulty they have understanding what they are reading, the more they need to depend on inner speech to make sense of the material.

People who lose their capacity for use inner speech due to brain impairments have reported memory problems as well as a reduced sense of identity. As one example, prominent neuroscientist Jill Bolte Taylor experienced a massive stroke in 1996 that resulted in a complete loss of inner speech. As she later described in her book,  My Stroke of Insight, losing inner speech also led to problems with self-awareness, loss of biographical memories, and even losing those emotions related to self-consciousness.

Along with all the other roles that inner speech seems to play, it likely comes as no surprise that inner speech seems to be important in terms of motivation as well. Whenever we find ourselves in a difficult competition, whether it involves writing an exam or playing an important game, we often use inner speech to “psych ourselves” up and make us feel more confident about our chances. For that matter, people suffering from depression or anxiety often find themselves using inner speech to ruminate on how bad life is and likelihood of failure.  For this reason, many different kinds of psychotherapy often involve teaching people how to use inner speech to overcome self-doubt and fear of failure by replacing negative self-talk with more positive inner speech.

One fascinating theory about  auditory hallucinations suggests that certain neurological or psychiatric conditions lead to people confusing inner speech with external voices. Brain imaging studies show that areas of the brain linked to language perception are often activated in people who report auditory hallucinations.   Many of these hallucinations tend to resemble inner speech in important ways. For example, people who are born deaf or who lost their hearing before they developed language tend not to experience auditory hallucinations the same way that hearing people do.

There may also be a link between inner speech and mind-wandering, or the tendency of our minds to “drift” whenever we are doing something monotonous. Also known as “decoupling,”  mind-wandering causes us to pay less attention to the world around us and focus more on our internal thoughts.   Inner speech can be an essential part of this kind of mind-wandering though actual research looking at this is still limited.

Despite all of the research studies that have been carried out so far, it is still far from clear exactly why humans evolved inner speech in the first place.  Though it may have originally developed as a tool for better verbal communication, our capacity for inner speech has expanded to become a critical part of our lives as human beings.   Not only does it to play an important role in making plans for the future, it is also helps us understand the world around us.

So learn to cultivate that inner voice, it’s an essential part of being human.

This is an edited version of Romeo Vitelli’s article, which was originally published on the blog Psychology Today on 31 August 2015.