Preparatory attention: Experiment and theory

This study investigated attention to a spatial location using a new spatial preparation task. Participants responded to a target dot presented in the center of a display and ignored a distracter dot presented to the right or left of the center. In an attempt to vary the level of preparatory attentio n directed to the target, the distracter dot was presented prior to the ons et time of the target and the relative frequency of distracter dots to targ et dots within a block of trials was varied. The results from the first thr ee experiments showed that when instructions induce weak preparatory attent ion to the target location, response times to a target on target-only trial s increase substantially as the percentage of trials containing a distracte r increases from 0 to 75%. In Experiments 2 and 3, instructions and display saliency were used to induce strong preparatory attention to the target lo cation, resulting in almost constant response times across distractor perce ntages. Experiment 4 varied percentage of target trials in the absence of d istracters, with the result that response times decreased as target trial p ercentage increased. Accounts of these data by early "activity-based" and l ate "criterion-based" attention theories are compared, and the early theory is given a more detailed description within the context of a cognitive neu roscience theory of attention. (C) 2000 Academic Press.