Abstract
In attentional capture research it is a robust finding that suddenly appearing stimuli or ‘sudden-onsets’ can capture attention in a purely exogenous or bottom-up manner. While some theorists (e.g. Yantis & Hillstrom, 1994) propose that this is because sudden-onsets represent new perceptual objects, it also seems plausible that subjects may be ‘set’ to attend to such dramatic changes, and that these endogenous or ‘top-down’ control settings are responsible for capture (e.g. Folk, Remington, and Wright, 1992). One impediment to evaluating these explanations has been that demonstrations of top-down modulation of sudden-onset capture have involved changing pre-cues, while demonstrations of the strongly bottom-up nature of sudden-onset capture have involved new objects appearing in locations previously unoccupied by placeholders. In two experiments we investigate the extent to which top-down modulation of attentional capture by new object sudden-onsets is possible. In Experiment 1 we found that the extent to which new object sudden-onset pre-cues capture attention is affected by a subject's task-set. Experiment 2 evaluated the impact of a constantly changing task-set in a task-switching paradigm, and once again modulation of new object sudden-onset capture was found. While these findings support the notion that some component of attentional capture by sudden-onsets is top-down in origin, the relatively small effects obtained still suggest a large role for an exogenous mechanism activated by new objects.