Abstract
This set of experiments revisits the issue whether all involuntary orienting is contingent on top-down goals. Specifically, the question was whether an abrupt onset captures attention in a non-contingent fashion. A variation of the Folk, Remington, and Johnston (1992) spatial pre-cueing paradigm was used. Observers searched a letter array for one of two target letters. Attention capture was assessed by the difference in reaction times to valid and invalid trials (target location correctly and incorrectly cued, respectively). To rule out the contingency explanation, one needs to ensure that (a) all features associated with the target, and (b) all visual features accompanying the search array's appearance, are excluded from the putative capture stimulus. We first established that when target location was color-defined, a color cue captured attention. But crucially, an onset cue also captured attention. In separate experiments, we ruled out explanations that (a) were based on the contingency between the onset cue and the transients accompanying the search array; (b) claimed that observers adopted a singleton-search strategy rather than monitoring specifically for the target-defining feature; and (c) assume that observers were monitoring motion, rather than specifically onset, transients. We showed that an onset captured attention even when the search array was not presented as an abrupt onset. We also showed that a color singleton failed to capture attention when the target's appearance may be construed as a singleton, suggesting that singleton-detection could not have been the observers' strategy. Finally, we showed that offset transients failed to capture attention when the target could be localized as a color singleton, implying that observers were not detecting transients per se. The evidence across the experiments support the view that an onset captures attention automatically, even though the top-down control settings may not be tuned specifically to monitoring onset transients.
NUS Grant R-581-000-078-750.