Predictors of Local and Global Processing in Autistic and Typical Development
Individuals with Autism Spectrum Disorder (ASD) have been shown to have a local processing bias: they are able to focus on the details of a visual display and ignore the overall whole and context (Mottron & Belleville, 1993; Mottron, Belleville, & Ménard, 1999). Typical individuals with the ability to draw realistically also show this local bias (Drake, Redash, Coleman, Haimson, & Winner, 2010; Drake & Winner, 2011). Two opposing theories have been proposed to account for the local processing bias in individuals with ASD. Some have argued that the local processing bias is at the expense of the ability to grasp the whole and that these individuals lack a "global bias" (Happé & Frith, 2006). According to this view, individuals with ASD have "weak central coherence." Mottron and his colleagues, however, have suggested that the local processing bias seen in ASD exists alongside intact global processing (Mottron & Belleville, 1993; Mottron et al., 1999). According to this view, individuals with ASD have "enhanced perceptual functioning." However, it is likely that these classifications overlook individual variations in local and global processing in the ASD and non-ASD population, some ASD and non-ASD individuals strong in both, weak in both, strong only in local, or strong only in global. If so it would be important to determine the predictors of each pattern, whether the same patterns of individual differences exist in the ASD and non-ASD population, and whether the predictors of each pattern are the same for ASD and non-ASD individuals. Four predictors of local and global processing (as assessed by a battery of tasks) were investigated: verbal IQ, nonverbal IQ, realistic drawing skill, and severity of ASD diagnosis. Participants in study 1 were non-ASD children; Participants in study 2 were ASD children; and those in study 3 were the combined sample of ASD and non-ASD children. Four major findings emerged. First, the predictors of local and global processing skill in the ASD population are the same as those in the non-ASD population. Second, the strongest predictor of local and global processing skills was realistic drawing skill, and not diagnosis, a novel finding. Third, as a group, ASD individuals performed no better and no worse on either local or global processing tasks than did non-ASD individuals, again a surprising and novel finding. Finally, and consistent with finding #2, children with strong performance in local and global processing also scored high in both drawing realism and nonverbal IQ.