Abstract
Plaisted and colleagues (J Child Psychol Psychiatry, 1998; JEP:HPP, 2001) demonstrated that children with autism are superior to typically developing children at visual search. They suggested that this superiority might be mediated by better memory for rejected distractors in autism. Horowitz & Wolfe (Nature, 1998) have previously argued that typical adults use little or no memory for rejected distractors. This conclusion relied on the randomized search paradigm in which a static control condition is compared to a dynamic condition in which stimuli are continually replotted during a trial, preventing any use of memory. If observers use memory in the static condition, RT X set size slopes would double in the dynamic condition. Studies on typical adults show similar slopes in the two conditions, though mean RTs are higher for dynamic search. We repeated this experiment with 18 children with autism and an age- and IQ-matched control group of typically developing children (ages 7–19). Measures of eye movement and RT were collected. The autism group responded faster than the control group. However, static and dynamic search were equally efficient for both groups. Children with autism do not use memory differently. Instead, they seem to respond more quickly once they locate a target. Analysis of eye movement patterns showed few differences between conditions or groups. Notably, neither group showed evidence of “sitting-and-waiting” for the target to come to them in the dynamic condition (c.f. von Mïhlenen et al., Psychol Sci, 2003).
NICHD/NIDCD CPEA U19-DC-03610, NIMH K01-MH-073944, AFOSR F49620-97-1-0045