The Visuo-Spatial Hierarchical Processing Trajectories of Typical and Atypical Development: A Neuroconstructivist Approach

Abstract

The work contained in this thesis was aimed at investigating the visuo-spatial hierarchical processing biases of children with fragile X syndrome (FXS) and autism. It is innovative in that it seeks to construct developmental trajectories for visuo-spatial abilities between the ages of 3 and 16 years. The clinical groups were compared against a trajectory for typically developing children. Results from a battery of standardised tests were analysed to demonstrate the similarities and differences between the developmental disorders. Study 1 examined the typical visuo-spatial hierarchical profile across a range of perception tasks, using the Navon task framework. A nonlinear pattern of development emerged, showing sensitivity to different stimuli formats. Study 2 employed a similar methodology within construction tasks. It was shown that young children display a disproportionate bias in constructing local elements but it disappears at around the age of 6, when differences even out. Study 3 investigates hierarchical processing across atypical development. All groups revealed an atypical pattern of results in both accuracy and reaction time data. Studies 4 and 5 shifted the focus to construction skills in atypical development. It was found that although those with high functioning autism were able to successfully complete the tasks, they did not develop typically. The FXS children also presented an atypical trajectory; they did not develop at all in construction tasks, performing similarly to 3 year old typically developing children, regardless of their age. The results demonstrated: (1) a lack of integration of executive function ability in FXS for successful task completion; (2) children with high functioning autism display a different profile to children with low functioning autism, leading to the conclusion that those with high functioning autism process global and local items independently, and those with low functioning autism process local at the expense of global items. This is something that has been debated in the autism literature for the past two decades but, the methodology adopted within this thesis has allowed for an indepth, cross-syndrome comparison that sheds light on the constraints that shape both typical and atypical development.

Date of Award	2010
Original language	English
Awarding Institution	Glasgow Caledonian University
Supervisor	Maria Nunez (Supervisor) & Christina Knussen (Supervisor)