Thursday, May 20, 2010
Franklin Hall B Level 4 (Philadelphia Marriott Downtown)11:00 AM
Background: Studies by Plaisted, O'Riordan and colleagues have shown that older children and adults with Autism Spectrum Disorders (ASD) are faster at finding targets in feature conjunction search displays (Plaisted, O'Riordan & Baron-Cohen, 1998; O'Riordan, Plaisted, Driver & Baron-Cohen, 2001). Currently, there is very little known about the visual search skills of very young children (1-3-year-olds), both typically developing or with ASD. Objectives: Our goal was to test if very young children with ASD (within a year of being diagnosed) show superior performance in visual search compared to typically developing toddlers. In order to do this, we adapted the classic visual search paradigm to be suitable for toddlers. Methods: Our paradigm required no verbal instructions and was based on minimal nonverbal feedback, making the task naturalistic for toddlers who are pre- or nonverbal. We used a Tobii T120 eye-tracker to measure fixation patterns. We tested toddlers with ASD (N = 17, mean age: 29 months) and typically developing toddlers matched on age (N = 14, mean age: 30 months) and on the Visual Reception scale of the Mullen Scales of Early Learning (N = 13, mean age: 23 months). All participants saw one, two or three blocks of trials depending on their mood and motivation. Each block consisted of 4 familiarization trials and 13 test trials (a random mix of 4 single feature trials (4 or 8 distractors) and 9 feature conjunction trials (4, 8 or 12 distractors)). Each test display was presented for 4 seconds. At the end of each trial, the target started spinning back and forth: we hoped that this event is interesting enough for toddlers to look for the target even before the spinning has started. We compared Time to First Fixation and Fixation Length for the target to the average of the distractor items that were fixated in any given trial. Results: Toddlers with ASD were not significantly faster, but were more successful at finding the target in conjunction search displays than either age-matched controls or controls matched on Visual Reception. Search times and success rates for single feature displays (pop-out) did not differ among the groups. Conclusions: The developmental trajectories of visual attentional processes start to diverge as early as 1-3 years of age in typically developing children vs. children with ASD.