Weak Central Coherence and Resistance to Distractor Inhibition in Children with Autism

Background:

Inhibition tasks that require resistance to distracting stimuli, such as Flanker Tasks, often reveal a deficit in children with autism (Christ et al., 2007).  However, on the classic Stroop task, a task requiring suppressing a prepotent response, children with autism appear to have intact inhibition, performing faster than typically developing children (Bryson, 1983).  These data may reflect a distinction between prepotent response and resistance to distractor inhibition (Friedman & Miyake, 2004), which may be differentially impaired in autism.

Objectives: : The current study investigated the possibility that children with autism may be impaired in resistance to distractor, while remaining unimpaired in prepotent response, inhibition.

Methods:

Three groups were assessed, 17 children with autism, 17 children with learning disabilities, and 17 typically developing children.  Groups were matched using the Raven’s Coloured Progressive Matrices Test.  All children were given 4 tasks, 2 of which were prepotent reponse tasks (antisaccade task, stop-signal task) and two of which were resistance to distractor tasks (flanker task, and abstract shape task).  During the antisaccade task, children identified the direction of arrows that appeared on uncued sides of the screen.  During the stop-signal task, children categorized pictures as animals or non-animals except when they heard a beep, where they were instructed to withhold response.  For the Flanker task, children identified the direction of a central arrow, which appeared flanked with congruently or incongruently pointing arrows.  Finally, in the abstract shape task children saw two green shapes side by side, sometimes with the left green shape overlapping a different red shape.  Children were asked to determine whether the two green shapes matched.

Results:

For the antisaccade task, the groups did not differ significantly in either time to make a response, F(1, 48) < 1, or number of errors, F(1, 48) < 1.  Similarly, on the stop-signal task there was no group effect on number of prepotent errors made, F(1,48) = 1.63, p = .21.  Interestingly, results from the 2 resistance to distractor tasks showed that while the groups performed comparably quickly on the tasks, F(1,48) < 1, children with autism made significantly less errors on the flanker task in the incongruent condition, F(1,48) = 4.29, p < .001.  The same trend, although not significant, was evident in the distractor condition of the shape task, F(1,48) = 1.71,  p= .19.

Conclusions:

These findings suggest that individuals with autism show intact inhibition, and certainly there is no evidence for problems on the prepotent response inhibition tasks.  However, while individuals with autism were as rapid as controls on the two resistance to distractor tasks, they made fewer errors in the conditions in which distractors were incongruent. This finding can clearly be explained in terms of a weak bias to central coherence in autism, which in this case makes competitor items in the global display less distracting.  This raises the question of whether individuals with autism would show inhibitory deficits on such tasks if they were made equally distracting for them as controls.