How Articulatory Suppression, Visual-Spatial Suppression and Private Speech Affect Planning in Autism Spectrum Disorder

Student thesis: Master's ThesisMaster of Science (MSc)


Much scientific evidence suggests that typically developing (TD) children transition from supporting goal-directed behaviour with visual-spatial processing to supporting goal-directed behaviour with dialogic inner speech, at the age of 7. Alternatively, research suggests that children with Autism Spectrum Disorder (ASD) over the age of 7 do not use inner speech, however, it is unclear whether this transition is absent (atypical development) in individuals with ASD or merely delayed (delayed development). Two experiments utilised the Tower of London task (computerised), under the conditions of silence, private speech, articulatory suppression and visual-spatial suppression to test these hypotheses. Both accuracy (number of moves over the minimum) and time taken were recorded. Experiment 1 tested children with and without ASD between the ages of 7 and 12 and Experiment 2 tested adults with and without ASD. There were no significant differences in intelligence between the ASD and TD groups in either Experiment 1 or 2. Neither Experiment 1, Experiment 2 or a post-hoc analysis which compared the data of both experiments found any significant group differences or significant interactions between group and condition. No significant effects on accuracy or significant effects of articulatory suppression were found. Only significant negative effects of visual-spatial suppression (for adults and children) and private speech (for adults) on time were found. No significant correlations were found between age and performance (relative to baseline) under the dual tasks for TD children or children with ASD. A significant negative correlation was found between baseline performance and relative performance (for time) under articulatory suppression in TD adults only. This pattern of results does not fit with what would be predicted by either the atypical or delayed development models and contradicts the previous literature (calling its replicability into question).
Date of Award24 Mar 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorChris Jarrold (Supervisor) & Melissa Allen (Supervisor)

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