Orienting of visual attention among persons with autism spectrum disorders : reading versus responding to symbolic cues

Persons with autism spectrum disorders (ASD) appear to be slower to interpret the meaning of symbolic cues. This could be because they are slower to read the symbolic cue, or because they are slower to select a response to the symbolic cue. Groups of participants with autism (n=11), participants with Asperger syndrome (n=9), and typically developing children (n=16) completed four forced-choice reaction time tasks to examine whether persons with ASD are slower to process the symbolic cue or slower to prepare a response to the cue. The participants completed two control conditions and two orienting conditions using non-predictive central arrow cues. In the Target and Cue conditions, participants gave a speeded response to the appearance of either a target (x) or a central arrow. In the Variable Cue Exposure (VCE) condition, the exposure time to the cue varied (100, 300, 600, or 1000 ms) and was followed by a 100 ms blank screen before the presentation of the target. In the Constant Cue Exposure (CCE) condition, all cues were presented for 100 ms and were followed by blank screens that varied in presentation length (100, 300, 600, or 1000 ms) before the presentation of the target. The results indicated that each group showed a unique pattern of responding. In both the Target and Cue conditions, participants with autism were slower than both Asperger syndrome and typically developing children. In both the VCE and CCE conditions, behavioural effects of the cue were found for participants with autism at longer SOAs than for Asperger syndrome, and at longer SOAs for Asperger syndrome than for typically developing children. These findings support the notion that persons with ASDs are impaired in their preparation of responses as opposed to impaired in reading the meaning of the cue. Further, both the ASD groups showed stronger facilitation effects at longer SOAs than typically developing children, indicating that they were less able to use cue predictability to mediate responding. The differences found between autism and Asperger syndrome are discussed in terms of developmental and clinical distinctions between the groups, and implications for theory and research design