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Michael Jenkins, Anna Grubert, Martin Eimer; The Effect of Distance on Voluntary Shifts of Attention between Visual Objects. Journal of Vision 2017;17(10):1327. doi: 10.1167/17.10.1327.
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© ARVO (1962-2015); The Authors (2016-present)
In many visual search tasks, attention shifts between objects can be guided by the visual properties of these objects, but there are conditions where such shifts are elicited in a fully endogenous (voluntary) fashion. Using the N2pc component of the event-related potential (ERP) as a marker of attentional object selection, we have previously shown that such voluntary movements of attention can be triggered within less than 200 ms. Here, we investigated whether the time required by voluntary attention shifts between two objects increases as a function of the spatial distance between them. Search displays contained seven grey letters or digits and an additional coloured circle (benchmark object) that were arranged in a circular fashion around central fixation. Participants' task was to report the identity (letter or digit) of one particular target object that was defined by its location relative to the benchmark. A cue presented prior to each search display signalled that the target would be one, two, or three positions from the benchmark (clockwise or anticlockwise, varied across blocks). N2pc components to benchmark objects preceded N2pcs to targets by about 100 ms, demonstrating that as intended, attention was first allocated to the benchmark before it was voluntarily re-allocated to the target object. Reaction times and errors increased linearly as a function of benchmark-target distance, suggesting longer shift times for larger distances. Surprisingly, the N2pc to target objects emerged at the same time for all distances. In a second experiment, we showed that N2pc components reflect the time point when the attentional focus moves into the contralateral hemifield rather than when it reaches the target. The N2pc associated with attention crossing the vertical meridian emerged later when the benchmark was further from the midline, suggesting that voluntary attention takes longer to shift to more distant locations.
Meeting abstract presented at VSS 2017
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