Imagine navigating through your day without that constant internal dialogue, the one that helps you plan, remember, and self-reflect. It might seem almost impossible to some, but new research has shown that not everyone experiences an inner voice. A groundbreaking study by Johanne Nedergård of the University of Copenhagen and Gary Lupyan of the University of Wisconsin-Madison has explored how the absence of this inner speech, a condition they term “anendophasia,” affects various cognitive tasks.
The research has been published in the journal Psychological Science.
The assumption that an inner voice is a universal human experience has influenced numerous studies on cognition and behavior. However, anecdotal evidence and personal narratives have suggested that some people do not have an inner voice. This prompted Nedergård and Lupyan to investigate whether the absence of inner speech affects cognitive tasks, particularly those involving verbal memory and language processing.
To select participants for their study, the researchers recruited individuals who had previously completed the Internal Representations Questionnaire (IRQ) in other unrelated studies. This questionnaire measures the extent to which people experience and rely on inner speech.
They specifically contacted participants who had scores on the Verbal factor of the IRQ either below 3.5 (placing them in the bottom 16 percent) or above 4.25 (placing them in the top 40 percent). For example, a high score on the Verbal factor might come from agreeing with statements like “I think about problems in my mind in the form of a conversation with myself.”
The final sample consisted of 93 participants, with 47 having high verbal scores and 46 having low verbal scores. These two groups were similar in terms of age, gender, education level, dyslexia, and first language. The researchers designed four experiments to assess the participants’ abilities in various cognitive tasks, with a particular focus on verbal memory and language processing.
The first experiment was a verbal memory task. Participants were asked to remember lists of words that were either phonologically similar (e.g., “bought,” “caught,” “taut,” and “wart”) or orthographically similar (e.g., “rough,” “cough,” “through,” “dough,” “bough”). The researchers hypothesized that inner speech aids in repeating and memorizing words internally, so those without an inner voice might struggle more with this task.
The second experiment was a rhyme judgment task. Participants were shown pairs of images and asked to judge whether the names of the objects rhymed (e.g., a sock and a clock). This task tested the participants’ ability to compare phonological information without relying on inner speech.
“It is a task that will be difficult for everyone, but our hypothesis was that it might be even more difficult if you did not have an inner voice because you have to repeat the words to yourself inside your head in order to remember them,” explained Nedergård.
“And this hypothesis turned out to be true: The participants without an inner voice were significantly worse at remembering the words. The same applied to an assignment in which the participants had to determine whether a pair of pictures contained words that rhyme, e.g. pictures of a sock and a clock. Here, too, it is crucial to be able to repeat the words in order to compare their sounds and thus determine whether they rhyme.”
The third experiment involved task switching, where participants alternated between different cognitive tasks, such as adding and subtracting numbers. The researchers aimed to determine if the lack of inner speech affected the participants’ ability to switch tasks quickly and accurately. The fourth and final experiment was a visual discrimination task, where participants were asked to distinguish between very similar figures, such as different silhouettes of cats and dogs, to explore whether inner speech plays a role in visual categorization and perception.
Interestingly, the researchers did not find significant differences between the two groups in the task-switching and visual discrimination experiments. This lack of difference suggests that people without an inner voice might use alternative strategies, such as physical cues, to manage task switching effectively. Additionally, the absence of significant differences in the visual discrimination task implies that inner speech might not be as crucial for visual categorization and perception as it is for verbal tasks.
“Maybe people who don’t have an inner voice have just learned to use other strategies. For example, some said that they tapped with their index finger when performing one type of task and with their middle finger when it was another type of task,” Nedergård remarked.
While the study highlights some cognitive differences related to the presence or absence of an inner voice, the practical implications for everyday life remain unclear. Johanne Nedergård points out that these differences might not significantly impact ordinary conversations but could be relevant in specific contexts like therapy. For instance, cognitive behavioral therapy often relies on inner dialogue to identify and change negative thought patterns, suggesting that the experience of therapy might differ for those without an inner voice.
“The short answer is that we just don’t know because we have only just begun to study it,” Nedergård said. “But there is one field where we suspect that having an inner voice plays a role, and that is therapy; in the widely used cognitive behavioural therapy, for example, you need to identify and change adverse thought patterns, and having an inner voice may be very important in such a process. However, it is still uncertain whether differences in the experience of an inner voice are related to how people respond to different types of therapy.”
“The experiments in which we found differences between the groups were about sound and being able to hear the words for themselves. I would like to study whether it is because they just do not experience the sound aspect of language, or whether they do not think at all in a linguistic format like most other people.”
The researchers acknowledge several limitations in their study. The reliance on self-reported measures of inner speech is one such limitation, as subjective assessments can sometimes be inaccurate. Additionally, the study’s sample size was relatively small, and further research with larger and more diverse populations is necessary to confirm these findings.
In future research, they aim to explore whether the absence of an inner voice affects other language areas. For instance, it remains to be seen whether people without an inner voice think in a fundamentally different way, perhaps relying more on visual or abstract thought processes. The researchers also plan to investigate the potential compensatory strategies that individuals without an inner voice might develop to navigate tasks typically aided by inner speech.
The study, “Not Everyone Has an Inner Voice: Behavioral Consequences of Anendophasia,” was published May 10, 2024.