Inner Speech Use in Autism

Abstract

Is the spontaneous recruitment of subvocal verbal mediation (inner speech) in High Functioning Autism (HFA) intact, impaired or simply uneven? Research into this area is still in its embryonic stage. This thesis aims to systematically review the current literature on inner speech functioning and then proceed to investigate the relationship between inner speech use and three keys areas of higher order cognitive functioning: working memory, categorisation and false belief reasoning. Inner speech use was measured by comparing performance of the various tasks under a silent condition and under the application of a dual-task paradigm (articulatory suppression). It was theorised that articulatory suppression would tie up any verbal resources necessary for subvocal mediation and as such would cause a detriment in performance when the task was performed under suppression. As predicted, the results showed an uneven profile in HFA’s recruitment of inner speech. On a task of working memory (measured by the Self-Ordered Pointing Task, Petrides and Milner, 1982), the use of subvocal language was found to be uneven. While under moderate cognitive load, inner speech recruitment was intact. However when cognitive load was increased to a critical level, HFA no longer recruited inner speech. An intact ability to recruit inner speech was found when the HFA group were tested on their ability to spontaneously categorise visually presented objects. Finally in a key area of false belief understanding in Theory of Mind (ToM) which is one of the cardinal impairments found in HFA, inner speech use was found to be impaired. Overall, the results of inner speech use appear to be intriguingly mixed with impairments in some areas and an intact ability in others. This is a very significant finding as it highlights and clarifies the direct relationship between an impaired ability to use inner speech and a measureable cognitive ability. As autism is a pervasive, lifelong developmental disability the wider implications of this research will also aid in informing others in curriculum development and teaching methodology to help those with autism cope better with their daily challenges. Finally, implications and directions for future research based will be discussed.