Age-Related Differences in Visual Interference Control in Adolescents with Autism Spectrum Disorder

Background: Given the countless sources of interference that one encounters on a moment-by-moment basis, the ability to filter and resist interference from visual distractors (RIVD) is essential for efficient functioning in everyday life.  Recent research in our laboratory (Christ et al., 2007, 2011) and others (e.g., Geurts et al., 2008) have documented impaired RIVD in individuals with autism spectrum disorder (ASD).  Within this context, results from a recent cross-sectional study (Christ et al., 2011) suggest that RIVD impairment may be more pronounced in young as compared to older adolescents with ASD.

Objectives: The objective of the present study was to replicate and extend previous findings of age-related differences in the magnitude of RIVD impairment experienced by children and adolescents with ASD.

Methods: A new sample of 36 participants with ASD (mean age: 14.5 years; range: 12.3 – 20 years) and a comparison group of 48 neurologically uncompromised participants without ASD (mean age: 15.6 yrs; range: 12.1-19.4 yrs) participated.  Similar to previous studies, we utilized a flanker visual filtering task to assess RIVD.  In this task, participants were shown a stimulus comprising a horizontal row of five fish-shaped stimuli (Rueda et al., 2004).  They were asked to respond as quickly as possible to the direction (left or right) that the center fish was facing.  The flanking stimuli (i.e., the two fish stimuli on each side of the target) could be either compatible (i.e., facing the same direction) or incompatible (i.e., facing the opposite direction) with the target.  RIVD ability was assessed by comparing performance between trials with incompatible flankers and trials with compatible flankers.

Results: Regression analyses were conducted to determine if a potential ASD-related impairment in RIVD emerged, remained static, or resolved across development. By utilizing this approach, we were able to control for the general contribution of age to RIVD, and evaluate whether any group differences in RIVD varied as a function of age.  The analysis revealed a significant interaction between age and group, pr²=.06, t(79)=2.19, p=.03.  Post hoc t-test comparisons confirmed that younger adolescents with ASD demonstrated a significantly larger RIVD effect (i.e., mean RT in the incompatible condition minus mean RT in the compatible condition) than their age-matched control counterparts (RIVD effect for participants age 16 years and younger:  ASD=56 ms, non-ASD=38 ms), t(57)=2.27, p=.03, d=.60.  No such difference, however, was observed for the older participants in the sample (RIVD effect for participants older than 16 years: ASD=37 ms, non-ASD=41 ms), t(23)<1, p=.69, d=.17. 

Conclusions: Taken together with other recent research (Christ et al., 2011), the present results support the hypothesis that children with ASD experience impairments in RIVD and this impairment is more evident in younger (as compared to older) children and adolescents with ASD. Given the potential clinical/academic implications associated with an age-related change in RIVD impairment (e.g., children may be at a major disadvantage if their early learning occurs with impaired RIVD), there is a clear need for additional longitudinal study to validate this finding.