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David Shiu, Jay Edelman; Instructing express saccades to shift in the face of large distractors. Journal of Vision 2006;6(6):483. doi: https://doi.org/10.1167/6.6.483.
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© ARVO (1962-2015); The Authors (2016-present)
Instructions (INS) to make a saccade to one side of a suddenly appearing visual stimulus array can affect the vector of express saccades (RTs: 80–110ms) with no sacrifice in RT (VSS 05). Here, we examined whether INS affected saccade vector when the stimulus array was placed at varying positions inside a much larger and more salient object. RTs and spatial effect of INS were measured in 6 tasks: Tasks 1–3) Frame present - 2 small squares (1°×1°) were separated horiz. (6°) inside a 16° x 6° frame (1° thick). Ss were instructed to saccade to the 1) left square 2) right square or 3) the stimulus display as whole. In each task, the frame appeared 0°,+/−3° horiz. w.r.t. the 2 squares. Ss were instructed to ignore the frame. Tasks 4–6) Like tasks 1–3, but no frame. INS were indicated by a central arrow prior to target onset. The 2 squares appeared at a random location on the screen. A 150–200ms gap was used to lower RT. The EMs of two Ss were recorded at 500Hz using an Eyelink II eyetracker. Saccade endpoint deviation in tasks 4–6 was regressed against instruction and of frame position. The effect of INS was found to be more than 2× that of frame position, despite the fact that the frame has an area 20× that of the 2 squares. Both instruction and frame presence had little effect on RT (<10ms). Thus, irrelevant visual objects of high salience can be rapidly filtered out by the saccadic system.
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