Not everyone uses inner speech, but those who do benefit in domains such as memory and self-control. Research shows inner speech varies widely, affecting cognitive and behavioral outcomes.
Most of us experience an internal voice, commonly referred to as an “inner voice” or “inner speech,” through which we reflect on our inner experiences. Inner speech enables us to engage in high-level cognitive functions, including self-control, attention and self-regulation. For instance, if our boss at work irritates us, we might try to regulate our response and manage our emotions through inner dialogue, explaining the situation to ourselves in our mind’s eye, to avoid directly confronting someone in a position of power relative to us.
This phenomenon can be defined as the manifestation of the subjective experience of language without its overt expression. Indeed, research indicates that external speech and inner speech share a common neural basis. While it was once assumed that inner speech was a universal experience—likely due to the natural human tendency to project our experiences onto others—recent findings reveal a wide spectrum of inner speech experiences among adults. These range from a continuous inner dialogue to a complete absence of inner speech.
Scientists previously believed that inner speech is a universal phenomenon; however, new findings indicate that some people do not experience it at all. A poster for the film Inside Out | Shutterstock, chingyunsong
Dialogue with Oneself
The modern study of inner speech likely began with the developmental psychologist, Lev Vygotsky. According to his theory, the process of language learning in toddlers is closely intertwined with their social interactions with those around them. Much of this early dialogue consists of instructions and comments from parents and other adults, as part of learning social rules. Over time, a child internalizes not only these rules, but also the use of language, to regulate their behavior. Initially, in preschool and early elementary school, such self-directed speech is typically done overtly and expressed aloud - a developmental stage known as private speech. Gradually, these external dialogues with the self become internalized and integrated into the child’s verbal thoughts. This process, according to Vygotsky, shapes inner speech.
Over the years, numerous hypotheses have been raised regarding the role of inner speech in domains such as emotional regulation, and in cognitive processes such as memory, behavioral control, planning, and problem-solving. Studying inner speech is challenging due to its nature as a psychological process without an observable external manifestation. However, over time, a range of direct and indirect methods have been developed to facilitate the study of inner speech. Most of these methods involve questionnaires about inner speech experiences, or tasks designed to disrupt inner speech.
Gradually, overt dialogues with oneself become internalized and embedded in the child’s verbal thoughts. A child talking to herself while playing | Shutterstock, Anokhina260758
Many studies on inner speech focus on its impact on skills related to behavioral management and planning, also known as “executive functions”. One of the central ones is working memory, previously referred to as "short-term memory”. This rapid-access memory system allows us to temporarily hold a limited amount of information for immediate use, essential for learning, problem-solving, and other cognitive processes. One of the most well-known applications of inner speech is its use in working memory: verbally memorizing a piece of information and repeating it over and over in our thoughts continuously helps refresh the memory, enhancing our ability to remember things in the short term—such as when we need to memorize a list or a series of numbers.
Inner speech sometimes also helps us absorb and process information, such as while reading. Additionally, it plays an important role in self-esteem, motivation, and task performance. It can also facilitate the learning and internalization of a second language.
When the Inner Voice Falls Silent
A recent study systematically examined the behavioral consequences of lacking inner speech. To do this, the researchers identified participants with high levels of inner speech, assigned them specific tasks, and compared their performance to that of participants with low levels of inner speech. To assess the participants' levels of inner speech, they were asked to complete a questionnaire where they rated their agreement with statements such as 'I think about problems in my head in the form of a conversation with myself.' The tasks selected were those the researchers hypothesized would be influenced by inner speech.
The tasks selected were those the researchers believed could be influenced by inner speech. A man writing in a notebook | Shutterstock, fizkes
Indeed, in a verbal memory task, the researchers found that participants who frequently used inner speech remembered more words. The researchers also tested whether the level of task performance changed if the participants spoke aloud during the task instead of using inner speech. This time the performance of participants who rarely use inner speech equaled that of participants who used it a lot. From this, it can probably be concluded that the key here is the mere use of verbal memorization of details, regardless of whether the speech is covert or overt.
In a task requiring analysis of word rhyming, the researchers again found that the group of participants with a high level of inner speech performed better than those who rarely used inner speech, and again, when the participants spoke out loud while performing the task, the performance of both groups equalized. In tasks involving task-switching as well as in tasks involving visual perception, inner speech had no effect on performance. The researchers hypothesized that these tasks may require fewer language-based strategies, or that participants employed alternative strategies to complete them.
The findings of the study suggest that inner speech can influence our behavior and functioning. The researchers proposed the term "Anendophasia" to describe the absence of inner speech, combining the Greek words for “absent,” “speech,” and “inner.” The study included not only individuals with full anendophasia but also those who scored low on the inner speech index - most participants used inner speech occasionally rather than avoiding it completely. Additionally, since the assessment of the level of inner speech was based on self-reporting, the rankings could be influenced by participants' self-perception and personal experience. The researchers highlight the necessity for more objective measurement methods, such as identifying neural correlates associated with inner speech.