Abstract
What does an individual with autism spectrum disorder (ASD) perceive first: the forest or the trees? In spite of 30 years of research and influential theories like the weak central coherence (WCC) theory and the enhanced perceptual functioning (EPF) account, the interplay of local and global visual processing in ASD remains only partly understood. Research findings vary in indicating a local processing bias or a global processing deficit, and often contradict each other. We have applied a formal meta-analytic approach and combined 56 articles that tested about 1,000 ASD participants and used a wide range of stimuli and tasks to investigate local and global visual processing in ASD. Overall, results show no enhanced local visual processing nor a deficit in global visual processing. Detailed analysis reveals a difference in the temporal pattern of the local-global balance, that is, slow global processing in individuals with ASD. Whereas task-dependent interaction effects are obtained, gender, age, and IQ of either participant groups seem to have no direct influence on performance. Based on the overview of the literature, suggestions are made for future research.
Highlights
Impact of Moderator Variables We considered the impact of six moderator variables, that is, level of visual processing, type of performance measure, type of task, gender, age, and IQ, as such moderator analyses allow us to answer under which specific conditions individuals with autism spectrum disorder (ASD) do or do not show a certain bias or deficit when compared to typically developing individuals
This article used formal meta-analysis to examine whether individuals with autism spectrum disorder differ in perceptual organization compared to typically developing individuals
Individuals with ASD are slower in global-order perception than typically developing individuals, in particular when having to attend to global order while incongruent information is present at the local level
Summary
Rather than yearning for new experimental research the existing literature is in need of an extensive, quantitative review of the available data, in which the overall effect size across different studies is assessed and the impact of potentially influential moderators and across-study differences are investigated. By analyzing large collections of data from individual studies, we aim (a) to examine the nature of atypicalities in perceptual organization in ASD, (b) to investigate how “local” and “global” visual processing relate to each other, and (c) to get a better idea of possible moderators that rule the diversity. A major problem with the existing research is that most studies differ in numerous ways, for instance, by employing different participant groups, different stimuli, or different task demands. The impact of such differences has been shown by several interesting studies. Koldewyn, Jiang, Weigelt, and Kanwisher (2013) provided evidence of an effect of task demands on the perceptual process in ASD, and Scherf, Behrmann, Kimchi, and Luna (2009; Scherf, Luna, Kimchi, Minshew, & Behrmann, 2008) demonstrated the importance of age effects on perceptual
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