Autism and a deficit in broadening the spread of visual attention.

BACKGROUND This study examines if visual attention in autism is spatially overfocused (Townsend & Courchesne, 1994) and if there is an associated deficit in broadening the spatial spread of attention. METHOD Two crosshairs were presented on each trial separated by a brief (500 ms) interval. There was a modest difference in the lengths of the two hairs in each crosshair and participants had to decide which one was longest. Previous research (Mack & Rock, 1998) has revealed that in making this judgement people spread their visual attention to embrace the whole crosshair. Varying the overall size of each crosshair was intended to control participants' spread of attention. The impact of the size of the first crosshair gave an indication of participants' default setting for the spread of attention. The impact of the size transition between the first and second crosshair gave an indication of the fluency with which participants could change the spatial spread of visual attention. RESULTS Based on the first proposal it was predicted that individuals with autism (N = 13), relative to ability-matched moderately learning disabled (N = 15) and typically developing individuals (N = 15), would be more accurate and quicker to respond when the first crosshair was small rather than large. However, the results revealed no effects of the size of the first crosshair and no group differences. Based on the second proposal it was predicted that individuals with autism, relative to both control groups, would be less accurate and slower to respond to the second crosshair when the size transition from the first crosshair involved a change from small to large (in comparison with large to large), but would not differ when the change was from large to small (in comparison with small to small). This prediction was confirmed. CONCLUSION Autism is associated with a deficit in broadening the spatial spread of visual attention. The implications of this for other visual and attentional anomalies observed in autism are discussed.