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Michael Jenkins, Anna Grubert, Martin Eimer; The speed of Voluntary Shifts of Attention . Journal of Vision 2016;16(12):589. doi: 10.1167/16.12.589.
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© ARVO (1962-2015); The Authors (2016-present)
Serial selection models of visual search assume that sequential shifts of attention between different objects can occur rapidly (~50ms) when they are guided by features of these objects. This assumption was recently confirmed with ERPs (Grubert & Eimer, in press). However, fully voluntary movements of attention may take considerably longer (~150-300ms; Horowitz et al., 2009). The present study investigated the speed of such purely endogenously driven attention shifts by examining the N2pc component of the event-related potential (ERP) as a marker of attentional object selection. Letters and digits in four different colours appeared in four locations. Participants had to report the alphanumeric category of the object (T2) that was in a specific location relative to another object in a known colour (T1). In this task, attention should be allocated first to T1 and then move to T2. Because T2 colour was unpredictable, attention shifts from T1 to T2 were not feature-guided, but had to be based on voluntary control processes. In Experiment 1, the direction of these shifts was determined on a trial-by-trial basis by the shape of T1. In Experiment 2, shift direction was pre-defined (clockwise or anticlockwise). The N2pc to T2 emerged around 100 ms later than the N2pc to T1 in Experiment 1, and around 150 ms later in Experiment 2. These results show that voluntary attention shifts are slower than feature-guided shifts, but can still be completed within less than 200 ms.
Meeting abstract presented at VSS 2016
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