Intact inner speech use in autism spectrum disorder: evidence from a short-term memory task.
Inner speech has been linked to higher-order cognitive processes including 'theory of mind', self-awareness and executive functioning, all of which are impaired in autism spectrum disorder (ASD). Individuals with ASD, themselves, report a propensity for visual rather than verbal modes of thinking. This study explored the extent to which children with ASD used inner speech or visual imagery to support recall from short-term memory. Twenty-five children with ASD and 20 comparison children with moderate learning disabilities completed an immediate serial recall task, in which stimuli consisted of items with either phonologically similar features, visuo-spatially similar features or control items which were neither visuo-spatially nor phonologically similar. ASD and comparison participants, with verbal mental ages above 7 years, recalled phonologically similar stimuli less well than control stimuli, indicating that both groups were using inner speech to recode visually presented information into a phonological code. In contrast, those participants with verbal mental ages below 7 years, whether with ASD or not, recalled visuo-spatially similar stimuli less well than control stimuli, indicating visual rather than phonological coding. This developmental pattern mirrors that found in typically developing children. Under experimental conditions, individuals with ASD use inner speech to the same extent as individuals without ASD of a comparable mental age.