Ming-Chou Ho and Paul Atchley
University of Kansas


Last year at OPAM, we demonstrated that the precedence of objects is necessary to evoke object-based attention (Ho, Atchley, Shellourne, and Hoffman, 2000). In the present work, we investigated how much time it takes for an object-based attentional representation to develop. Observers detected a target embedded in overlapping dashed lines. A cue (70% validity) was also presented. The SOA between the cue and objects was varied (cue before target/objects by 75 and 150 ms, cue and objects simultaneously presented, or object preceded cue by 75 and 150 ms). As before, when target and objects were presented simultaneously, no object-based effects were found. Also, object-based effects occurred in the 150 ms SOA case (objects before cue) but not the 75 ms SOA case, suggesting that object-based representations do not occur instantaneously.