Ask a researcher – Is there research to investigate the inner voice?

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Has any research been done to investigate the inner voice (internal monologue) in people with Asperger’s Syndrome?

OTARC’s answer

There has been quite a bit of research on inner speech with a brief summary of findings provided below, including links to some of the research publications.

There is quite a lot of research evidence that inner speech (also sometimes called ‘private speech’ or ‘covert private speech’) is important to complete complex cognitive tasks (such as thinking, planning, remembering, problem solving) in typically developing children and adults. Preschool children are often seen (and heard) talking aloud to themselves, especially when they are engaged in a difficult task or solving a problem. This narration helps their performance of that task or problem. It is thought that this ‘overt private speech’ is internalised with age and develops into inner speech by about 7 years (Williams, Happé & Jarrold, 2008). Sometimes, when older children are engaged in a particularly difficult problem solving task they may whisper, stick their tongue out or move their lips as if they were talking. This also largely disappears with age, although there are some studies that show overt private speech in adults, especially when completing difficult tasks (Duncan & Cheyne 2002). Often they are not aware that they are doing so.

There is no longitudinal evidence that shows us how and when inner speech develops in children on the autism spectrum, including Asperger’s Syndrome. But we do know that these children and adults do not seem to employ inner speech to perform cognitive tasks as readily as children without autism. As a result, their performance on these tasks tends to suffer (see for example, Whitehouse, Maybery & Durkin, 2006; Wallace et al, 2012; Williams, Bowler & Jarrold, 2012). In addition, the performance of individuals with lower verbal and communication skills tends to suffer more than that of higher-functioning individuals.

However, not all cognitive tasks seem to be equally affected. For example, Williams et al (2012) found that performance on a short-term memory task was the same in adults with and without autism when they were allowed to use inner speech for rehearsal of the to-be-remembered items. When rehearsal by inner speech was prevented (the researchers asked them to do another task simultaneously), memory performance dropped by the same extent in each group. But when doing a task which tested planning ability (the Tower of London task), the performance of adults with autism indicated that they were NOT using inner speech to assist them, while the adults without autism did so. These finding indicates that inner speech may be used by adults on the autism spectrum for some cognitive tasks (remembering) but not for others (planning). The researchers argued that speaking to one-self may be sufficient to learn to use inner speech for rehearsal, but we learn to use inner speech to help us with planning activities by communicating with others, something people on the Autism spectrum are not very good at. In other words, the ability to plan actions depends on a different type of inner speech than ability for short-term memory recall. The former is learned by communicating with others, but the latter is learned by communicating with one-self (rehearsal).

Some argue that rather than using inner speech people with autism think in pictures. See for example the video below by Temple Grandin, who makes a very strong argument for this theory from her own experience. There is also some early evidence that this may be the case. Hurlburt, Happé and Frith (1994) asked three adults with Asperger’s Syndrome to keep written records of their “inner experiences” at regular intervals while engaged in their everyday life activities. In subsequent interviews with the researchers, they were asked specifically whether their inner experiences were in the form of speech, visual images, feelings, or some other format. The results showed that two of the three participants seemed to think primarily or exclusively in images; the third did not seem to have any inner thoughts, possibly because he was relatively low functioning. None of the three described their experiences in terms of inner speech.

The findings from the three adults contrast with the results of the other studies, described above, which showed that for at least some tasks people with Autism do use inner speech. So, how can we explain these apparent differences in findings? First of all, many studies have shown that people in general are not very good at describing and remembering what is going on in their mind, in particular when they are asked to describe cognitive processes like the ones we are talking about here. But this does not mean that the inner experiences of Hurburt et al’s participants and their description of them should be dismissed. Perhaps people with autism DO implement inner speech in their everyday lives, but do not always conceive of and/or report this inner dialog. Given their other difficulties associated with autism, they may have come to see their inner thoughts as images and report them as such, as was the case in Hurlburt et al’ study (Williams, et al, 2008).

In conclusion, while early studies using self reports of inner thoughts seem to indicate that people with autism may think exclusively in images, later careful experiments show that this is not the case. They DO use inner speech to help their performance in recall tasks, but may be less proficient using it in planning tasks. The implication of these findings is that interventions aimed at improving social communication may also lead to improvements in the use of inner speech. Training could involve teaching children and adults with autism to talk aloud or whisper to themselves while engaging in tasks. This overt private speech may help to improve their inner speech and awareness of it. As well, practicing writing down inner experiences (whether visual or verbal) might be a worthwhile endeavour for people on the spectrum.


Temple Grandin’s video:

Duncan, R.M. & Cheyne, J.A. (2002). Private speech in young adults: Task difficulty, self-regulation, and psychological predication. Cognitive Development, 16, 889-906.

Hurlburt, R.T., Happé, F. & Frith, U. (1994). Sampling the form of inner experience in three adults with Asperger Syndrome. Psychological Medicine, 24, 385-395.,%20Happe%20and%20Frith,%20Sampling%20the%20form%20of%20inner%20experience%20in%20three%20adults%20with%20Asperger%20syndrome%20copy.pdf

Wallace, G.L., Silvers, J.A., Martin A. & Kenworthy, L.E. (2009). Brief report: Further evidence for inner speech deficits in autism spectrum disorders. Journal of Autism and Developmental Disorders, 39, 1735–1739. for full paper.

Whitehouse, A.J.O., Maybery, M.T. & Durkin, K. (2006). Inner speech impairments in autism. Journal of Child Psychology and Psychiatry, 47, 857-865.

Williams, D., Happé, F. & Jarrold, C. (2008). Intact inner speech use in autism spectrum disorder: evidence from a short-term memory task. Journal of Child Psychology and Psychiatry 49, 51–58.

Williams, D.M., Bowler, D.M. & Jarrold, C. (2012). Inner speech is used to mediate short-term memory, but not planning, among intellectually high-functioning adults with autism spectrum disorder. Development and Psychopathology, 24, 225–239. for full paper.

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