Abstract
In the object substitution masking (OSM) phenomenon, briefly shown targets can be masked by presenting four small dots that surround the targets but do not touch it (Enns & Di Lollo, 1997). The purpose of the present study was to determine if masking stimuli that are present and visible, but not attended to, can generate OSM. In other words, must the masking stimuli be attended to in order for OSM to occur? To accomplish this, we used top-down attentional control settings, which have profound effects on what sort of stimuli capture attention; stimuli that have features that match a target capture attention while stimuli that mismatch with target features are ignored. In our experiment, subjects were told to locate a target (distinguished by color from distractors) and to identify a feature on the target, thus creating an attentional control set for that color. Four-dot masks with either the same (mask-target match) or different color (mask-target mismatch) as the target were presented at SOAs ranging from -144 to 144 ms. When subjects searched for green targets, masking was enhanced if the four-dot mask was also green (match) as opposed to red (mismatch). This difference was largest 48 ms after target offset. Also, there was no difference between color match and mismatch masks when there was no attentional control set for green. Thus, the present results cannot be attributed simply to mask-target color congruency effects but rather the interplay of attention and vision. Specifically, our results show that masking is considerably enhanced when the four-dot mask falls within the subject’s attentional control set. Overall, this suggests that object substitution masking is mediated partly by attention and subject to top-down attention control.
Meeting abstract presented at VSS 2012