Draft:Anendophasia

In a 2024 study published in Psychological Science, the researchers recruited 93 participants who had previously been assessed with the Internal Representations Questionnaire (IRQ)^[4] and selected 46 who scored in the lowest fifth for inner speech and 47 who scored in the highest fifth.^[1] The researchers conducted four experiments:

• Verbal working memory: Five words were briefly shown and the participants were asked to repeat them back. The low inner speech group performed significantly worse.
• Rhyme judgment: The participants were shown pairs of object images and asked whether the names of the objects rhymed. The low inner speech group was less accurate and slower.
• Task switching: The participants switched between addition and subtraction. No significant difference between groups was found.
• Perceptual categorization: The participants were asked to distinguish silhouettes from the same or different categories. No significant difference between groups was found.

When the participants in both groups reported to have spoken aloud during the verbal tasks, the group differences disappeared, and it was suggested that the external vocalization compensated for the absence of inner speech.^[1] The researchers concluded that the people with low inner speech might use other cognitive strategies for tasks that are normally associated with inner verbal rehearsal.

It is estimated that 5–10 percent of the population have little or no inner speech according to self-report data from the IRQ.^[1]

In a 2025 commentary in Psychological Science, Andreas Lind (Lund University) wrote that the findings of Nedergaard and Lupyan show differences in the prevalence of inner speech but do not give strong evidence that there is anyone who has no inner speech.^[5] He wrote that the "low inner speech" group in the study was taken from the bottom fifth of self-report scores on one questionnaire and that many of those in the group reported some inner speech. Charles Fernyhough (Durham University) also warned against the framing of anendophasia as a distinct condition and in favour of the view that inner speech exists on a continuum of individual variation.^[5]

Nedergaard and Lupyan have recognised this and wrote that recruiting people with very low inner speech scores is a priority for future research to find out if there is anyone who has no inner speech.^[1]

Anendophasia is often discussed in the same way as aphantasia (absence of visual mental imagery) and anauralia (absence of inner hearing of music and sounds) as all three involve differences in internal sensory or linguistic representation rather than deficits in external perception or language ability.^[1] As with aphantasia, anendophasia is not associated with reduced intelligence or language ability and people with little inner speech have full control of language but do not simulate it auditorily during thinking.

The co-occurrence of anendophasia and aphantasia has been noted in self-reporting communities, and some researchers have suggested that these conditions may be part of a continuum of variation in internal mental representation.^[1]

Nedergaard has suggested that differences in inner speech may have implications for cognitive behavioural therapy (CBT), which is based on the identification and modification of verbal thought patterns. People with little inner speech may react differently to therapy that assumes a verbal internal dialogue.^[1] Lupyan has suggested that people with more inner speech may be more severely affected by language impairments after stroke as they rely more on internal verbal processing.^[1]

Researchers in education have noted that differences in children's inner speech may affect reading and writing development.^[1]