Eye-Tracking Established As a Reliable Test-Retest Measure in Adolescents with ASD: Visual Attention to Social and Non-Social Stimuli

Background: Prior research suggests that eye gaze patterns can be useful for quantifying social interest and motivation in individuals with autism spectrum disorder (ASD) and neurotypical controls (Jones et al., 2008), and to characterize phenotypic differences between these two groups (Klin et al., 2002; Nakano et al., 2010). Clinically, these findings are relevant because they highlight the core social deficits of ASD and suggest that eye tracking may be a valuable tool for identifying potential behavioral markers and measuring treatment response. Although test-retest reliability of eye tracking measures has recently been demonstrated in other disorders (e.g., Fragile X Syndrome, Farzin et al., 2011), it has yet to be established in ASD. Demonstrating the test-retest reliability of eye gaze measures in persons with ASD is essential if these are to be used as a stable measure of intervention efficacy, as well as in early detection studies.

Objectives: To assess the test-retest reliability of an eye tracking measure of attention to social and non-social stimuli in adolescents with ASD.

Methods: Nineteen males aged 12-17 (M=14.3, SD=1.7) with a diagnosis of ASD and full-scale IQ ranging from 47-133 (M=92.9, SD=22.4) participated in the present study at Time 1 and Time 2, separated by an interval of 9 weeks. Sitting approximately 60 cm from a 17-inch display, participants passively viewed six 10-second arrays of 12 static images (adapted from Sasson et al., 2008) while a Tobii X120 infrared eye tracker collected gaze information as part of a larger battery of studies. Pictures were classified as either social (e.g., a person smiling) or non-social (e.g., a train), and were selected to be relatively similar in complexity and size. Gaze variables of interest included Total Fixation Duration (i.e., proportion of time spent looking at social and non-social images relative to the total amount of time spent looking at both types of images), Fixation Count (i.e., proportion of times a social or non-social image was fixated relative to the total number of fixations made), and Visit Count (i.e., proportion of visits made to social or non-social stimuli relative to the total number of visits made).

Results: Intraclass correlation coefficients (ICC) and Pearson correlation coefficients were computed for each gaze variable, comparing looking patterns at Time 1 to looking patterns at Time 2. Results revealed moderate correlations in Total Fixation Duration (ICC=.537, p=.007; r=.55, p<.05) and Fixation Count (ICC=.535, p=.008; r=.54, p<.05) to social and non-social stimuli, and a strong correlation in Visit Count (ICC=.769, p=.000; r=.77, p<.01) at Times 1 and 2.

Conclusions: Using a modified set of established stimuli, this study provides evidence for the test-retest reliability of gaze patterns to static social and non-social images in adolescents with ASD. Although preliminary, these findings suggest that future behavioral or medical intervention studies may be able to use eye tracking as a reliable outcome measure gauging treatment response.