Thursday, May 20, 2010
Franklin Hall B Level 4 (Philadelphia Marriott Downtown)11:00 AM
Background: Eye tracking technology holds promise as an objective methodology for characterizing the early features of autism. While patterns of eye gaze have been found to be abnormal in 2-year-olds with autism (Jones et al., 2009), a recent study suggests that eye scan paths may not be deviant in the first year of life (Young et al., 2009). The degree to which preference and motivation mediate normal and abnormal visual scan patterns is unclear. For example, Klin and colleagues (2009) utilized a preferential looking paradigm and found a reduced preference for biological motion in 2-year-olds with autism. Thus, what an infant prefers to look at may be a more clearly definable indicator of risk than how he looks at something. When given the direct choice, typically developing toddlers prefer to look at social images over non-social images. It is unknown if this same preference exists in toddlers at-risk for autism. At older ages children with autism are often superior in local processing of geometric patterns and prefer to visually attend to real world repetition such as the moving blade of a fan. Objectives: To determine if toddlers at risk for an autism spectrum disorder (ASD) prefer to look at dynamic geometric patterns over social images, the age at which such preference emerges, and the degree to which preferential looking patterns can discriminate toddlers at-risk for an ASD from those at-risk for a language delay (LD) and developmental delay (DD) as well as typically developing (TD) controls. Methods: Using a population based screening method, toddlers at-risk for an ASD, language delay (LD) and developmental delay (DD) as young as 12-months were recruited and tracked. Ninety toddlers ranging between 12-42 months with later confirmed diagnoses participated (33 ASD; 35 TD; 11 LD; 11 DD, mean age = 23 months). Toddlers viewed a movie consisting of simultaneous images of dynamic geometric patterns (GP) on one side and children in action on the other. Duration of fixation was determined using a TOBII eye tracker and preference was defined as looking time > 50% towards one movie type. Results: Overall, toddlers at-risk for an ASD spent significantly more time looking at GP than TD, t(66) = 3.33, p <.05 and toddlers with a LD t(42) = 2.1, p <.05. Thirty three percent of the ASD group spent more than 50% of their time fixated on GP movies in contrast to only 5% of typical, 9% of LD and 10% of DD toddlers. Of the ASD toddlers who preferred GP, over half spent > 70% of their time visually examining GPs, with several toddlers exceeding 90% GP viewing time, a pattern not found in any other group. Thus, when 70% GP viewing time is used as a cut off, the positive predictive value for ASD is 100%. Furthermore, a GP preference was found in the ASD group as young as 14 months. Conclusions: A preference for geometric patterns may be a risk factor for autism and is observable in some toddlers by 14 months in age.