Abstract
Recently there has been increasing evidence for the predominant role top-down controls play in attentional selection. Here we showed that in the spatial cueing task, though only the goal-matched stimulus was selected, task-irrelevant salient stimuli still had higher priority in processing. In five experiments, the cue was designed to be either contingent on the target feature (i.e., a red cue) or it was not contingent (an onset, form, or luminance cue), and the cued item was manipulated to be the target, the response compatible/incompatible distractor, or the response unrelated distractor. Two effects were measured across different stimulus onset asynchronies (SOAs): the validity effect (i.e., the cued item was the target vs. non-target) and the response compatibility effect (i.e., the cued item was a response compatible distractor vs. incompatible distractor). We found both effects for the red cue at 0, 50, 100, and 250 ms SOAs, while the onset cue showed the compatibility effect at 100 ms SOA, and the validity effect at 250 ms SOA (Experiments 1–3). When the display size was increased from 4 to 8, the compatibility effect was observed for a form cue at 0 ms SOA (Experiment 4), so as a luminance cue at 150 ms SOA (Experiment 5). Thus, both the validity and compatibility effects were observed in all SOA conditions for a contingent cue; and only the compatibility effect at short SOAs and only the validity effect at long SOAs were observed for non-contingent cues. A parallel interactive model was proposed to explain these results. In this model, the activation level of each item is determined by bottom-up and top-down factors at the selection stage. After that, a decision is made if the decision threshold is met. With this model, results of the five experiments and several previous important findings are successfully simulated.
Supported by the National Science Council of Taiwan, NSC92-2413-H-002-026