This blog post is a response to an Ask an autism researcher question from 2016.
Has any research been done to investigate the inner voice (internal monologue) in Autistic people?
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.
The role of inner speech in cognitive tasks
There is quite a lot of research evidence that inner speech (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 often talk 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. This ‘overt private speech’ is thought to be internalised with age and develops into inner speech by about 7 years (Williams, Happé & Jarrold, 2008).
Development of inner speech in non-Autistic children
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 behaviour largely disappears with age, although some studies show overt private speech in adults, especially when completing difficult tasks (Duncan & Cheyne 2002). Often they are not aware that they are doing so.
Inner speech in Autistic children and adults
There is no longitudinal evidence yet that explains how and when inner speech develops in Autistic children. However, research shows that Autistic children and adults may not employ inner speech in the same way as non-Autistic individuals, which can influence their performance on certain cognitive tasks (see for example, Whitehouse, Maybery & Durkin, 2006; Wallace et al, 2012; Williams, Bowler & Jarrold, 2012). Additionally, individuals with varying levels of verbal and communication abilities may face more significant challenges in these tasks compared to those with fewer support needs.
Differentiating inner speech in memory and planning tasks
However, not all cognitive tasks seem to be equally affected. For example, Williams, Bowler & Jarrold (2012) found Autistic and non-Autistic adults performed equally well on a short-term memory task when they were allowed to use inner speech for rehearsal of the to-be-remembered items. However, when the researchers prevented them from using inner speech by assigning a simultaneous task, memory performance dropped by the same amount in both groups. But when doing a task which tested planning ability (the Tower of London task), the performance of Autistic adults indicated that they were NOT using inner speech to assist them, while non-Autisic adults did. These finding indicates that Autsitcic adults may use inner speech 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 plan activities by communicating with others, something Autistic people may experience challenges with. 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 through communication with others, while the latter is learned through self-communication (rehearsal).
Do Autistic people think in pictures?
Some argue that rather than using inner speech Autistic people think in pictures. See for example the video by Temple Grandin, who makes a 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 Autistic adults to regularly keep written records of their “inner experiences” while engaging in everyday activities. Researchers asked specifically whether their inner experiences were in the form of speech, visual images, feelings, or some other format in subsequent interviews. The results showed that two of the three participants seemed to think primarily or exclusively in images; the participant did not report any inner thoughts, which may be related to individual differences in Autistic traits or communication styles. None of the three described their experiences in terms of inner speech.
The complexity of self-reported inner experiences
The findings from the three adults contrast with the results of the other studies, described above, which showed that for at least some tasks Autistic people do use inner speech. So, how can we explain these apparent differences in findings? First, many studies have shown that people generally are not very good at describing and remembering what is going on in their mind, particularly when asked to describe cognitive processes like the ones we discuss here. But this does not mean we should dismiss the inner experiences of Hurburt et al’s participants and their description of them. Perhaps Autistic people DO implement inner speech in their everyday lives, but do not always conceive of and/or report this inner dialog. Given their other differences associated with autism, they may have come to see their inner thoughts as images and report them as such, as in Hurlburt et al’ study (Williams, Happé & Jarrold, 2008).
Practical implications for supporting Autistic people
In conclusion, while early studies using self reports of inner thoughts seem to indicate that Autistic people 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. These findings imply that supporting social communication may also contribute to improvements in inner speech use for some individuals. Training could involve teaching Autistic children and adults 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 Autistic people.
