Object-based attention: sensory enhancement or scanning prioritization.

The three experiments reported here test whether object-modulated attentional spreading can be obtained when the target location is 100% certain. Experiment 1 uses the reaction time (RT)-based flanker task similar to Shomstein and Yantis (2002), and replicates the null result of the object-modulated attentional spreading. RT and accuracy (ACC) have been shown to reflect different processes: postperceptual decision vs. perceptual process (Santee & Egeth, 1982). Experiment 2 adopts the data-limited ACC-based measure and reports that attention could spread within the attended object. To avoid ceiling effects, Experiment 3 adjusts the presentation time based on the trials where the target and flankers were compatible and on the same objects, and provides the convergent evidence supporting the object-modulated attentional spreading. These results suggest that because the RT-based measure is less sensitive in reflecting the quality of perceptual representations, it is not sufficiently a strong evidence to distinguish between sensory enhancement and scanning prioritization accounts.