Abstract
The issue whether attentional capture is determined by top-down control settings or it can be purely stimulus-driven remains unsolved. We have shown previously that only a visual onset, but not color, can capture attention in a purely stimulus-driven fashion (Yeh & Liao, 2008, 2010). Here we propose that whether top-down control settings take the determinative role in attentional capture depends on stimulus property. Visual onset is unique in capturing attention due to its transient property that can be escaped from the modulation of top-down controls. In contrast, a sustained color signal which allows more time for top-down signal to exert its effect captures attention only when the color is contingent with top-down control settings. We test this hypothesis by adopting a spatial cueing paradigm, in which two types of cues (onset and color) were followed by either one of the two types of targets to examine whether the cue captures attention depending on its contingency with the target-defining feature as well as the stimulus property. To further explore the underlying mechanisms of attentional capture by onset and color, we manipulated the cue-to-target stimulus-onset-asynchrony (SOA) to examine how the capture effect varies with time. Results showed that the onset cue captured attention regardless of the target type in short but not long SOA conditions. In contrast, the color cue captured attention only when the target was defined by color, and the capture effect lasted until long SOAs. Taken together, the results suggest that attentional capture by onset can be purely stimulus-driven whereas attentional capture by color is contingent on top-down control settings. We suggest that different underlying mechanisms are responsible for attentional capture by onset and color respectively, with the former resulting from exogenous orienting and the latter, feature-based attention enhancement.
This study is supported by grants from Taiwan's National Science Council, 96-2413-H-002-009-MY3, 98-2410-H-002-023-MY3, 098-2811-H-002-034, and 099-2811-H-002-038.