Eye movements, visual attention, and autism: a saccadic reaction time study using the gap and overlap paradigm

Abstract

Background: On the basis of the literature on autism, it was hypothesized that children with autism have deficits in attentional (dis-)engagement mechanisms.Methods: A saccadic gap-overlap task was used to study visual engagement and disengagement in 16 high-functioning autistic children of about 10 years of age and 15 age- and IQ-matched normal control children. Subjects were asked to make saccadic eye movements from a fixation point to a suddenly appearing target as fast as possible. The saccadic reaction time was compared in two conditions: 1) the overlap condition, in which the fixation point was continuously visible, and 2) the gap condition, in which the fixation point was turned off 200 msec before the target appeared.Results: Although no differences between the groups in either condition was observed, the gap effect (i.e., the difference in saccadic reaction time between the overlap condition and the gap condition) was smaller in the autistic group than in the control group.Conclusions: We concluded that autistic children show a lower level of attentional engagement.