Abstract
What happens when we shift attention towards a specific location? Most models of spatial attention assume that attention operates like a spotlight and that stimuli appearing in the focus of attention are mandatorily processed. In contrast to this claim, we provide evidence that shifting attention to a location can be dissociated from extracting an object's identity at that location (attentional engagement). Participants searched for two red targets embedded in one of two visual streams of gray distractors. Prior to the second target, a red distractor (cue) appeared either in the same or in the other stream relative to the target. It appeared either during the period of the attentional blink triggered by the first target or outside the blink. Finally, it enclosed a stimulus that elicited a response that was either compatible or incompatible with the response elicited by the target. We show that attentional capture by the cue remained intact during the blink, whereas the response compatibility effect (indicative of attentional engagement) was reduced during the AB. This dissociation allowed us to clarify the mechanisms underlying a widely used electrophysiological index of spatial attention, the N2pc. We replicated our first study, while also measuring ERPs. We show that the N2pc component was suppressed during the blink, whereas the lateralized P1 component, which is known to reflect spatial allocation of attention, was not. The contribution of these findings is twofold. First, they suggest that attentional engagement does not necessarily follow attentional shifting, which opens the door for a new model of spatial attention. Second, they show that the N2pc does not index attentional shifting but attentional engagement.
Meeting abstract presented at VSS 2018