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Leslie Drummond, Sarah Shomstein; Object-based attention: Attentional certainty vs. attentional shifting. Journal of Vision 2008;8(6):553. doi: 10.1167/8.6.553.
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© ARVO (1962-2015); The Authors (2016-present)
The finding that visual attention is often object-based (e.g., Egly et al., 1994) is no longer disputed in the literature. However, the mechanism underlying object-based attentional selection remains to be a subject of investigations. Recent studies put forth two different mechanisms that give rise to object-based attentional effects. The first suggests that attentional uncertainty is driving object-based effects (i.e., attentional prioritization account) — when target location is unknown, locations within the cued object receive greater attentional priority. The opposing view suggests that object-based effects are observed whenever attentional shifts are demanded, such that objects guide attentional shifting. We used a modified Egly paradigm to investigate directly, by pitting attentional certainty against attentional shifting, which of the two suggested mechanisms is indeed responsible for object-based effects. In a series of experiments we manipulated (1) certainty of target position, (2) shifting of attention (i.e., target appearing in a different location than a cue thus requiring an attentional shift), and (3) the cue to target SOA (100, 300, and 500ms). We observed a complete reduction of the object-based effect, across all SOAs, when attentional shifting was required but attentional certainty was high (i.e., 100% certainty). These results suggest that attentional uncertainty, and not a mere shift of attention, gives rise to object-based guidance of attentional selection. In addition, these results land further support for attentional prioritization account of object-based attention, and provide further constraints on the mechanisms of object-based selection.
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