Thesis advisor: Ellen Winner / 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. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

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<p>Previous studies have reported inconsistent results for people with Autism Spectrum Disorders (ASD) in both biological motion and Navon tasks. Each of these tasks require both local and global processing and were used in this study to compare processing styles of both ASD and typical groups. In the biological motion study, the ASD and the typical groups completed an emotion and a direction-discrimination experiment with happy and angry point-light walkers, which were presented in four different stimulus conditions: upright, inverted, scrambled and random. Overall, the ASD group had higher reaction times and lower accuracy, but the effect of condition did not differ between groups. Both groups performed worse in terms of accuracy and reaction times in the scrambled (i.e., local information only) conditions, therefore revealing a global bias in the processing of biological motion information. In the Navon task study with the same participants, typical individuals exhibited a global precedence effect, manifested as lower reaction times for global stimuli as well as global interference in “look for only local digits” task. However, individuals in the ASD group did not, on average, show a local or a global bias. In a subsequent analysis, the ASD group was divided into locally-biased and globally-biased sub-groups. Now, when a three way analysis between typical and the two ASD groups was performed, the globally-biased group’s performance was not distinguishable from that of the typical group, while no global bias was observed for the locally-biased group. When these two groups were compared on the Biological Motion study, the locally-biased group had no reaction time difference across conditions including both biological motion and Navon tasks, unlike the globally-biased group, who displayed higher reaction times for the scrambled condition, just like the typical group did. Therefore, it is possible that the inconsistencies in the local-global processing literature of individuals with ASD may have resulted because the studies did not account for individual differences in processing styles within the ASD groups that may be variable, unlike typical individuals who have a global bias for most tasks.</p> / Master of Science (MSc)

Perceptual grouping describes the organization of small elements into larger objects. Research in user interface (UI) design has demonstrated effects of perceptual grouping on attention and navigation. However, grouping can be mediated by a variety of task factors. One such mediator is processing time. Recent discoveries in vision science suggest that elemental grouping can occur in more than one way, depending on how long elements are displayed. These findings have led to a new understanding of perceptual organization of elements in real-world spatial environments. However,these findings had not been explored within the context of UI environments. Time limits to UI are often set by task demands. Exposure time limits may affect perceptual grouping of elements in UI. Here I report a series of experiments that tested global and local pushbutton grouping by time in user interface displays. The research question was to determine whether global or local depictions of pushbutton groupings speed interaction with user interface. Global and local groupings were compared because prior researchers have discovered that global scene properties can be perceived before local scene properties. For this reason, it was hypothesized that global, as opposed to local, depictions of pushbutton groupings would speed human-interface interactions. Global grouping was defined as grouping by relatively large shapes whereas local grouping was defined as grouping by shapes that were relatively small. The difference between global and local grouping was quantitative and defined by comparison. Participants saw pushbutton interface displays on a computer monitor for varied exposure durations and were asked to make decisions about the grouping of pushbuttons in these displays. Responses and reaction times were recorded. The results of the reported experiments suggest that global, as compared to local, groupings are more accessible across stimulus durations. They also suggest that global groupings can be utilized faster than local groupings in unlimited exposures. Taken together, the reported results further our understanding of global and local Gestalt grouping in user interface displays.

Pas de résumé / The thesis investigated the development of children’s global/local processing hierarchical patterns introduced by Navon (1977). The objectives were to understand more comprehensively the developmental characteristics of children’s perception through their global and local processing of hierarchical patterns, by considering the effects of age, stimuli properties, duration of exposure to the stimuli and gender in a perceptual task and a drawing task. These effects were tested in 3 different populations: typically developing children, children with mental retardation and early blind children. The results revealed that typically developing children attended to both the local and global level of processing but these modes of spatial information processing operated independently. In a first step, children before 4 years of age showed dominance of local processing and then a more global processing developed at 4 years of age, and at 5 years of age integrated responses began to emerge. Early blind children showed similar developmental characteristics, although there was a protracted period of local processing dominance. Indeed, these children mainly produced local responses at ages of between 6 and 10 years, and then developed more global responses at 11-12 years and continued to integrate the two levels of analysis at later ages. On the other hand, global dominance was shown in children with mental retardation and their development was affected more by mental age than by chronological age. Moreover, their responses were shown to be sensitive to the fact that meaningful object could be located at the local level, enhancing local processing in this case. These results need further confirmations as the studies of global/local processing in atypical children are not numerous. In particular, the effect of duration of exposure to the stimuli should be further analyzed, because this factor did not seem to have a great effect in our experiments while it seemed more powerful in other studies carried out with adults. Replication of the study with children with mental retardation appears also important to plan for future work, because we can have some doubt relatively the absence of modification through ages of the way these children perceive hierarchical patterns. Finally, defining more precisely what may underlie the gender differences seems also worth to explore since gender did not show a major effect in our results.

The thesis investigated the development of children's global/local processing hierarchical patterns introduced by Navon (1977). The objectives were to understand more comprehensively the developmental characteristics of children's perception through their global and local processing of hierarchical patterns, by considering the effects of age, stimuli properties, duration of exposure to the stimuli and gender in a perceptual task and a drawing task. These effects were tested in 3 different populations: typically developing children, children with mental retardation and early blind children. The results revealed that typically developing children attended to both the local and global level of processing but these modes of spatial information processing operated independently. In a first step, children before 4 years of age showed dominance of local processing and then a more global processing developed at 4 years of age, and at 5 years of age integrated responses began to emerge. Early blind children showed similar developmental characteristics, although there was a protracted period of local processing dominance. Indeed, these children mainly produced local responses at ages of between 6 and 10 years, and then developed more global responses at 11-12 years and continued to integrate the two levels of analysis at later ages. On the other hand, global dominance was shown in children with mental retardation and their development was affected more by mental age than by chronological age. Moreover, their responses were shown to be sensitive to the fact that meaningful object could be located at the local level, enhancing local processing in this case. These results need further confirmations as the studies of global/local processing in atypical children are not numerous. In particular, the effect of duration of exposure to the stimuli should be further analyzed, because this factor did not seem to have a great effect in our experiments while it seemed more powerful in other studies carried out with adults. Replication of the study with children with mental retardation appears also important to plan for future work, because we can have some doubt relatively the absence of modification through ages of the way these children perceive hierarchical patterns. Finally, defining more precisely what may underlie the gender differences seems also worth to explore since gender did not show a major effect in our results.